LCOV - code coverage report
Current view: top level - src/bin/pg_rewind - xlogreader.c (source / functions) Hit Total Coverage
Test: PostgreSQL 18devel Lines: 377 722 52.2 %
Date: 2024-07-19 16:11:31 Functions: 19 28 67.9 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * xlogreader.c
       4             :  *      Generic XLog reading facility
       5             :  *
       6             :  * Portions Copyright (c) 2013-2024, PostgreSQL Global Development Group
       7             :  *
       8             :  * IDENTIFICATION
       9             :  *      src/backend/access/transam/xlogreader.c
      10             :  *
      11             :  * NOTES
      12             :  *      See xlogreader.h for more notes on this facility.
      13             :  *
      14             :  *      This file is compiled as both front-end and backend code, so it
      15             :  *      may not use ereport, server-defined static variables, etc.
      16             :  *-------------------------------------------------------------------------
      17             :  */
      18             : #include "postgres.h"
      19             : 
      20             : #include <unistd.h>
      21             : #ifdef USE_LZ4
      22             : #include <lz4.h>
      23             : #endif
      24             : #ifdef USE_ZSTD
      25             : #include <zstd.h>
      26             : #endif
      27             : 
      28             : #include "access/transam.h"
      29             : #include "access/xlog_internal.h"
      30             : #include "access/xlogreader.h"
      31             : #include "access/xlogrecord.h"
      32             : #include "catalog/pg_control.h"
      33             : #include "common/pg_lzcompress.h"
      34             : #include "replication/origin.h"
      35             : 
      36             : #ifndef FRONTEND
      37             : #include "pgstat.h"
      38             : #else
      39             : #include "common/logging.h"
      40             : #endif
      41             : 
      42             : static void report_invalid_record(XLogReaderState *state, const char *fmt,...)
      43             :             pg_attribute_printf(2, 3);
      44             : static void allocate_recordbuf(XLogReaderState *state, uint32 reclength);
      45             : static int  ReadPageInternal(XLogReaderState *state, XLogRecPtr pageptr,
      46             :                              int reqLen);
      47             : static void XLogReaderInvalReadState(XLogReaderState *state);
      48             : static XLogPageReadResult XLogDecodeNextRecord(XLogReaderState *state, bool nonblocking);
      49             : static bool ValidXLogRecordHeader(XLogReaderState *state, XLogRecPtr RecPtr,
      50             :                                   XLogRecPtr PrevRecPtr, XLogRecord *record, bool randAccess);
      51             : static bool ValidXLogRecord(XLogReaderState *state, XLogRecord *record,
      52             :                             XLogRecPtr recptr);
      53             : static void ResetDecoder(XLogReaderState *state);
      54             : static void WALOpenSegmentInit(WALOpenSegment *seg, WALSegmentContext *segcxt,
      55             :                                int segsize, const char *waldir);
      56             : 
      57             : /* size of the buffer allocated for error message. */
      58             : #define MAX_ERRORMSG_LEN 1000
      59             : 
      60             : /*
      61             :  * Default size; large enough that typical users of XLogReader won't often need
      62             :  * to use the 'oversized' memory allocation code path.
      63             :  */
      64             : #define DEFAULT_DECODE_BUFFER_SIZE (64 * 1024)
      65             : 
      66             : /*
      67             :  * Construct a string in state->errormsg_buf explaining what's wrong with
      68             :  * the current record being read.
      69             :  */
      70             : static void
      71           0 : report_invalid_record(XLogReaderState *state, const char *fmt,...)
      72             : {
      73             :     va_list     args;
      74             : 
      75           0 :     fmt = _(fmt);
      76             : 
      77           0 :     va_start(args, fmt);
      78           0 :     vsnprintf(state->errormsg_buf, MAX_ERRORMSG_LEN, fmt, args);
      79           0 :     va_end(args);
      80             : 
      81           0 :     state->errormsg_deferred = true;
      82           0 : }
      83             : 
      84             : /*
      85             :  * Set the size of the decoding buffer.  A pointer to a caller supplied memory
      86             :  * region may also be passed in, in which case non-oversized records will be
      87             :  * decoded there.
      88             :  */
      89             : void
      90           0 : XLogReaderSetDecodeBuffer(XLogReaderState *state, void *buffer, size_t size)
      91             : {
      92             :     Assert(state->decode_buffer == NULL);
      93             : 
      94           0 :     state->decode_buffer = buffer;
      95           0 :     state->decode_buffer_size = size;
      96           0 :     state->decode_buffer_tail = buffer;
      97           0 :     state->decode_buffer_head = buffer;
      98           0 : }
      99             : 
     100             : /*
     101             :  * Allocate and initialize a new XLogReader.
     102             :  *
     103             :  * Returns NULL if the xlogreader couldn't be allocated.
     104             :  */
     105             : XLogReaderState *
     106          78 : XLogReaderAllocate(int wal_segment_size, const char *waldir,
     107             :                    XLogReaderRoutine *routine, void *private_data)
     108             : {
     109             :     XLogReaderState *state;
     110             : 
     111             :     state = (XLogReaderState *)
     112          78 :         palloc_extended(sizeof(XLogReaderState),
     113             :                         MCXT_ALLOC_NO_OOM | MCXT_ALLOC_ZERO);
     114          78 :     if (!state)
     115           0 :         return NULL;
     116             : 
     117             :     /* initialize caller-provided support functions */
     118          78 :     state->routine = *routine;
     119             : 
     120             :     /*
     121             :      * Permanently allocate readBuf.  We do it this way, rather than just
     122             :      * making a static array, for two reasons: (1) no need to waste the
     123             :      * storage in most instantiations of the backend; (2) a static char array
     124             :      * isn't guaranteed to have any particular alignment, whereas
     125             :      * palloc_extended() will provide MAXALIGN'd storage.
     126             :      */
     127          78 :     state->readBuf = (char *) palloc_extended(XLOG_BLCKSZ,
     128             :                                               MCXT_ALLOC_NO_OOM);
     129          78 :     if (!state->readBuf)
     130             :     {
     131           0 :         pfree(state);
     132           0 :         return NULL;
     133             :     }
     134             : 
     135             :     /* Initialize segment info. */
     136          78 :     WALOpenSegmentInit(&state->seg, &state->segcxt, wal_segment_size,
     137             :                        waldir);
     138             : 
     139             :     /* system_identifier initialized to zeroes above */
     140          78 :     state->private_data = private_data;
     141             :     /* ReadRecPtr, EndRecPtr and readLen initialized to zeroes above */
     142          78 :     state->errormsg_buf = palloc_extended(MAX_ERRORMSG_LEN + 1,
     143             :                                           MCXT_ALLOC_NO_OOM);
     144          78 :     if (!state->errormsg_buf)
     145             :     {
     146           0 :         pfree(state->readBuf);
     147           0 :         pfree(state);
     148           0 :         return NULL;
     149             :     }
     150          78 :     state->errormsg_buf[0] = '\0';
     151             : 
     152             :     /*
     153             :      * Allocate an initial readRecordBuf of minimal size, which can later be
     154             :      * enlarged if necessary.
     155             :      */
     156          78 :     allocate_recordbuf(state, 0);
     157          78 :     return state;
     158             : }
     159             : 
     160             : void
     161          78 : XLogReaderFree(XLogReaderState *state)
     162             : {
     163          78 :     if (state->seg.ws_file != -1)
     164           0 :         state->routine.segment_close(state);
     165             : 
     166          78 :     if (state->decode_buffer && state->free_decode_buffer)
     167          78 :         pfree(state->decode_buffer);
     168             : 
     169          78 :     pfree(state->errormsg_buf);
     170          78 :     if (state->readRecordBuf)
     171          78 :         pfree(state->readRecordBuf);
     172          78 :     pfree(state->readBuf);
     173          78 :     pfree(state);
     174          78 : }
     175             : 
     176             : /*
     177             :  * Allocate readRecordBuf to fit a record of at least the given length.
     178             :  *
     179             :  * readRecordBufSize is set to the new buffer size.
     180             :  *
     181             :  * To avoid useless small increases, round its size to a multiple of
     182             :  * XLOG_BLCKSZ, and make sure it's at least 5*Max(BLCKSZ, XLOG_BLCKSZ) to start
     183             :  * with.  (That is enough for all "normal" records, but very large commit or
     184             :  * abort records might need more space.)
     185             :  *
     186             :  * Note: This routine should *never* be called for xl_tot_len until the header
     187             :  * of the record has been fully validated.
     188             :  */
     189             : static void
     190          78 : allocate_recordbuf(XLogReaderState *state, uint32 reclength)
     191             : {
     192          78 :     uint32      newSize = reclength;
     193             : 
     194          78 :     newSize += XLOG_BLCKSZ - (newSize % XLOG_BLCKSZ);
     195          78 :     newSize = Max(newSize, 5 * Max(BLCKSZ, XLOG_BLCKSZ));
     196             : 
     197          78 :     if (state->readRecordBuf)
     198           0 :         pfree(state->readRecordBuf);
     199          78 :     state->readRecordBuf = (char *) palloc(newSize);
     200          78 :     state->readRecordBufSize = newSize;
     201          78 : }
     202             : 
     203             : /*
     204             :  * Initialize the passed segment structs.
     205             :  */
     206             : static void
     207          78 : WALOpenSegmentInit(WALOpenSegment *seg, WALSegmentContext *segcxt,
     208             :                    int segsize, const char *waldir)
     209             : {
     210          78 :     seg->ws_file = -1;
     211          78 :     seg->ws_segno = 0;
     212          78 :     seg->ws_tli = 0;
     213             : 
     214          78 :     segcxt->ws_segsize = segsize;
     215          78 :     if (waldir)
     216          78 :         snprintf(segcxt->ws_dir, MAXPGPATH, "%s", waldir);
     217          78 : }
     218             : 
     219             : /*
     220             :  * Begin reading WAL at 'RecPtr'.
     221             :  *
     222             :  * 'RecPtr' should point to the beginning of a valid WAL record.  Pointing at
     223             :  * the beginning of a page is also OK, if there is a new record right after
     224             :  * the page header, i.e. not a continuation.
     225             :  *
     226             :  * This does not make any attempt to read the WAL yet, and hence cannot fail.
     227             :  * If the starting address is not correct, the first call to XLogReadRecord()
     228             :  * will error out.
     229             :  */
     230             : void
     231        5148 : XLogBeginRead(XLogReaderState *state, XLogRecPtr RecPtr)
     232             : {
     233             :     Assert(!XLogRecPtrIsInvalid(RecPtr));
     234             : 
     235        5148 :     ResetDecoder(state);
     236             : 
     237             :     /* Begin at the passed-in record pointer. */
     238        5148 :     state->EndRecPtr = RecPtr;
     239        5148 :     state->NextRecPtr = RecPtr;
     240        5148 :     state->ReadRecPtr = InvalidXLogRecPtr;
     241        5148 :     state->DecodeRecPtr = InvalidXLogRecPtr;
     242        5148 : }
     243             : 
     244             : /*
     245             :  * Release the last record that was returned by XLogNextRecord(), if any, to
     246             :  * free up space.  Returns the LSN past the end of the record.
     247             :  */
     248             : XLogRecPtr
     249      355436 : XLogReleasePreviousRecord(XLogReaderState *state)
     250             : {
     251             :     DecodedXLogRecord *record;
     252             :     XLogRecPtr  next_lsn;
     253             : 
     254      355436 :     if (!state->record)
     255      182866 :         return InvalidXLogRecPtr;
     256             : 
     257             :     /*
     258             :      * Remove it from the decoded record queue.  It must be the oldest item
     259             :      * decoded, decode_queue_head.
     260             :      */
     261      172570 :     record = state->record;
     262      172570 :     next_lsn = record->next_lsn;
     263             :     Assert(record == state->decode_queue_head);
     264      172570 :     state->record = NULL;
     265      172570 :     state->decode_queue_head = record->next;
     266             : 
     267             :     /* It might also be the newest item decoded, decode_queue_tail. */
     268      172570 :     if (state->decode_queue_tail == record)
     269      172570 :         state->decode_queue_tail = NULL;
     270             : 
     271             :     /* Release the space. */
     272      172570 :     if (unlikely(record->oversized))
     273             :     {
     274             :         /* It's not in the decode buffer, so free it to release space. */
     275           0 :         pfree(record);
     276             :     }
     277             :     else
     278             :     {
     279             :         /* It must be the head (oldest) record in the decode buffer. */
     280             :         Assert(state->decode_buffer_head == (char *) record);
     281             : 
     282             :         /*
     283             :          * We need to update head to point to the next record that is in the
     284             :          * decode buffer, if any, being careful to skip oversized ones
     285             :          * (they're not in the decode buffer).
     286             :          */
     287      172570 :         record = record->next;
     288      172570 :         while (unlikely(record && record->oversized))
     289           0 :             record = record->next;
     290             : 
     291      172570 :         if (record)
     292             :         {
     293             :             /* Adjust head to release space up to the next record. */
     294           0 :             state->decode_buffer_head = (char *) record;
     295             :         }
     296             :         else
     297             :         {
     298             :             /*
     299             :              * Otherwise we might as well just reset head and tail to the
     300             :              * start of the buffer space, because we're empty.  This means
     301             :              * we'll keep overwriting the same piece of memory if we're not
     302             :              * doing any prefetching.
     303             :              */
     304      172570 :             state->decode_buffer_head = state->decode_buffer;
     305      172570 :             state->decode_buffer_tail = state->decode_buffer;
     306             :         }
     307             :     }
     308             : 
     309      172570 :     return next_lsn;
     310             : }
     311             : 
     312             : /*
     313             :  * Attempt to read an XLOG record.
     314             :  *
     315             :  * XLogBeginRead() or XLogFindNextRecord() and then XLogReadAhead() must be
     316             :  * called before the first call to XLogNextRecord().  This functions returns
     317             :  * records and errors that were put into an internal queue by XLogReadAhead().
     318             :  *
     319             :  * On success, a record is returned.
     320             :  *
     321             :  * The returned record (or *errormsg) points to an internal buffer that's
     322             :  * valid until the next call to XLogNextRecord.
     323             :  */
     324             : DecodedXLogRecord *
     325      177718 : XLogNextRecord(XLogReaderState *state, char **errormsg)
     326             : {
     327             :     /* Release the last record returned by XLogNextRecord(). */
     328      177718 :     XLogReleasePreviousRecord(state);
     329             : 
     330      177718 :     if (state->decode_queue_head == NULL)
     331             :     {
     332           0 :         *errormsg = NULL;
     333           0 :         if (state->errormsg_deferred)
     334             :         {
     335           0 :             if (state->errormsg_buf[0] != '\0')
     336           0 :                 *errormsg = state->errormsg_buf;
     337           0 :             state->errormsg_deferred = false;
     338             :         }
     339             : 
     340             :         /*
     341             :          * state->EndRecPtr is expected to have been set by the last call to
     342             :          * XLogBeginRead() or XLogNextRecord(), and is the location of the
     343             :          * error.
     344             :          */
     345             :         Assert(!XLogRecPtrIsInvalid(state->EndRecPtr));
     346             : 
     347           0 :         return NULL;
     348             :     }
     349             : 
     350             :     /*
     351             :      * Record this as the most recent record returned, so that we'll release
     352             :      * it next time.  This also exposes it to the traditional
     353             :      * XLogRecXXX(xlogreader) macros, which work with the decoder rather than
     354             :      * the record for historical reasons.
     355             :      */
     356      177718 :     state->record = state->decode_queue_head;
     357             : 
     358             :     /*
     359             :      * Update the pointers to the beginning and one-past-the-end of this
     360             :      * record, again for the benefit of historical code that expected the
     361             :      * decoder to track this rather than accessing these fields of the record
     362             :      * itself.
     363             :      */
     364      177718 :     state->ReadRecPtr = state->record->lsn;
     365      177718 :     state->EndRecPtr = state->record->next_lsn;
     366             : 
     367      177718 :     *errormsg = NULL;
     368             : 
     369      177718 :     return state->record;
     370             : }
     371             : 
     372             : /*
     373             :  * Attempt to read an XLOG record.
     374             :  *
     375             :  * XLogBeginRead() or XLogFindNextRecord() must be called before the first call
     376             :  * to XLogReadRecord().
     377             :  *
     378             :  * If the page_read callback fails to read the requested data, NULL is
     379             :  * returned.  The callback is expected to have reported the error; errormsg
     380             :  * is set to NULL.
     381             :  *
     382             :  * If the reading fails for some other reason, NULL is also returned, and
     383             :  * *errormsg is set to a string with details of the failure.
     384             :  *
     385             :  * The returned pointer (or *errormsg) points to an internal buffer that's
     386             :  * valid until the next call to XLogReadRecord.
     387             :  */
     388             : XLogRecord *
     389      177718 : XLogReadRecord(XLogReaderState *state, char **errormsg)
     390             : {
     391             :     DecodedXLogRecord *decoded;
     392             : 
     393             :     /*
     394             :      * Release last returned record, if there is one.  We need to do this so
     395             :      * that we can check for empty decode queue accurately.
     396             :      */
     397      177718 :     XLogReleasePreviousRecord(state);
     398             : 
     399             :     /*
     400             :      * Call XLogReadAhead() in blocking mode to make sure there is something
     401             :      * in the queue, though we don't use the result.
     402             :      */
     403      177718 :     if (!XLogReaderHasQueuedRecordOrError(state))
     404      177718 :         XLogReadAhead(state, false /* nonblocking */ );
     405             : 
     406             :     /* Consume the head record or error. */
     407      177718 :     decoded = XLogNextRecord(state, errormsg);
     408      177718 :     if (decoded)
     409             :     {
     410             :         /*
     411             :          * This function returns a pointer to the record's header, not the
     412             :          * actual decoded record.  The caller will access the decoded record
     413             :          * through the XLogRecGetXXX() macros, which reach the decoded
     414             :          * recorded as xlogreader->record.
     415             :          */
     416             :         Assert(state->record == decoded);
     417      177718 :         return &decoded->header;
     418             :     }
     419             : 
     420           0 :     return NULL;
     421             : }
     422             : 
     423             : /*
     424             :  * Allocate space for a decoded record.  The only member of the returned
     425             :  * object that is initialized is the 'oversized' flag, indicating that the
     426             :  * decoded record wouldn't fit in the decode buffer and must eventually be
     427             :  * freed explicitly.
     428             :  *
     429             :  * The caller is responsible for adjusting decode_buffer_tail with the real
     430             :  * size after successfully decoding a record into this space.  This way, if
     431             :  * decoding fails, then there is nothing to undo unless the 'oversized' flag
     432             :  * was set and pfree() must be called.
     433             :  *
     434             :  * Return NULL if there is no space in the decode buffer and allow_oversized
     435             :  * is false, or if memory allocation fails for an oversized buffer.
     436             :  */
     437             : static DecodedXLogRecord *
     438      177718 : XLogReadRecordAlloc(XLogReaderState *state, size_t xl_tot_len, bool allow_oversized)
     439             : {
     440      177718 :     size_t      required_space = DecodeXLogRecordRequiredSpace(xl_tot_len);
     441      177718 :     DecodedXLogRecord *decoded = NULL;
     442             : 
     443             :     /* Allocate a circular decode buffer if we don't have one already. */
     444      177718 :     if (unlikely(state->decode_buffer == NULL))
     445             :     {
     446          78 :         if (state->decode_buffer_size == 0)
     447          78 :             state->decode_buffer_size = DEFAULT_DECODE_BUFFER_SIZE;
     448          78 :         state->decode_buffer = palloc(state->decode_buffer_size);
     449          78 :         state->decode_buffer_head = state->decode_buffer;
     450          78 :         state->decode_buffer_tail = state->decode_buffer;
     451          78 :         state->free_decode_buffer = true;
     452             :     }
     453             : 
     454             :     /* Try to allocate space in the circular decode buffer. */
     455      177718 :     if (state->decode_buffer_tail >= state->decode_buffer_head)
     456             :     {
     457             :         /* Empty, or tail is to the right of head. */
     458      177718 :         if (required_space <=
     459      177718 :             state->decode_buffer_size -
     460      177718 :             (state->decode_buffer_tail - state->decode_buffer))
     461             :         {
     462             :             /*-
     463             :              * There is space between tail and end.
     464             :              *
     465             :              * +-----+--------------------+-----+
     466             :              * |     |////////////////////|here!|
     467             :              * +-----+--------------------+-----+
     468             :              *       ^                    ^
     469             :              *       |                    |
     470             :              *       h                    t
     471             :              */
     472      177718 :             decoded = (DecodedXLogRecord *) state->decode_buffer_tail;
     473      177718 :             decoded->oversized = false;
     474      177718 :             return decoded;
     475             :         }
     476           0 :         else if (required_space <
     477           0 :                  state->decode_buffer_head - state->decode_buffer)
     478             :         {
     479             :             /*-
     480             :              * There is space between start and head.
     481             :              *
     482             :              * +-----+--------------------+-----+
     483             :              * |here!|////////////////////|     |
     484             :              * +-----+--------------------+-----+
     485             :              *       ^                    ^
     486             :              *       |                    |
     487             :              *       h                    t
     488             :              */
     489           0 :             decoded = (DecodedXLogRecord *) state->decode_buffer;
     490           0 :             decoded->oversized = false;
     491           0 :             return decoded;
     492             :         }
     493             :     }
     494             :     else
     495             :     {
     496             :         /* Tail is to the left of head. */
     497           0 :         if (required_space <
     498           0 :             state->decode_buffer_head - state->decode_buffer_tail)
     499             :         {
     500             :             /*-
     501             :              * There is space between tail and head.
     502             :              *
     503             :              * +-----+--------------------+-----+
     504             :              * |/////|here!               |/////|
     505             :              * +-----+--------------------+-----+
     506             :              *       ^                    ^
     507             :              *       |                    |
     508             :              *       t                    h
     509             :              */
     510           0 :             decoded = (DecodedXLogRecord *) state->decode_buffer_tail;
     511           0 :             decoded->oversized = false;
     512           0 :             return decoded;
     513             :         }
     514             :     }
     515             : 
     516             :     /* Not enough space in the decode buffer.  Are we allowed to allocate? */
     517           0 :     if (allow_oversized)
     518             :     {
     519           0 :         decoded = palloc(required_space);
     520           0 :         decoded->oversized = true;
     521           0 :         return decoded;
     522             :     }
     523             : 
     524           0 :     return NULL;
     525             : }
     526             : 
     527             : static XLogPageReadResult
     528      177718 : XLogDecodeNextRecord(XLogReaderState *state, bool nonblocking)
     529             : {
     530             :     XLogRecPtr  RecPtr;
     531             :     XLogRecord *record;
     532             :     XLogRecPtr  targetPagePtr;
     533             :     bool        randAccess;
     534             :     uint32      len,
     535             :                 total_len;
     536             :     uint32      targetRecOff;
     537             :     uint32      pageHeaderSize;
     538             :     bool        assembled;
     539             :     bool        gotheader;
     540             :     int         readOff;
     541             :     DecodedXLogRecord *decoded;
     542             :     char       *errormsg;       /* not used */
     543             : 
     544             :     /*
     545             :      * randAccess indicates whether to verify the previous-record pointer of
     546             :      * the record we're reading.  We only do this if we're reading
     547             :      * sequentially, which is what we initially assume.
     548             :      */
     549      177718 :     randAccess = false;
     550             : 
     551             :     /* reset error state */
     552      177718 :     state->errormsg_buf[0] = '\0';
     553      177718 :     decoded = NULL;
     554             : 
     555      177718 :     state->abortedRecPtr = InvalidXLogRecPtr;
     556      177718 :     state->missingContrecPtr = InvalidXLogRecPtr;
     557             : 
     558      177718 :     RecPtr = state->NextRecPtr;
     559             : 
     560      177718 :     if (state->DecodeRecPtr != InvalidXLogRecPtr)
     561             :     {
     562             :         /* read the record after the one we just read */
     563             : 
     564             :         /*
     565             :          * NextRecPtr is pointing to end+1 of the previous WAL record.  If
     566             :          * we're at a page boundary, no more records can fit on the current
     567             :          * page. We must skip over the page header, but we can't do that until
     568             :          * we've read in the page, since the header size is variable.
     569             :          */
     570             :     }
     571             :     else
     572             :     {
     573             :         /*
     574             :          * Caller supplied a position to start at.
     575             :          *
     576             :          * In this case, NextRecPtr should already be pointing either to a
     577             :          * valid record starting position or alternatively to the beginning of
     578             :          * a page. See the header comments for XLogBeginRead.
     579             :          */
     580             :         Assert(RecPtr % XLOG_BLCKSZ == 0 || XRecOffIsValid(RecPtr));
     581        5148 :         randAccess = true;
     582             :     }
     583             : 
     584      177718 : restart:
     585      177718 :     state->nonblocking = nonblocking;
     586      177718 :     state->currRecPtr = RecPtr;
     587      177718 :     assembled = false;
     588             : 
     589      177718 :     targetPagePtr = RecPtr - (RecPtr % XLOG_BLCKSZ);
     590      177718 :     targetRecOff = RecPtr % XLOG_BLCKSZ;
     591             : 
     592             :     /*
     593             :      * Read the page containing the record into state->readBuf. Request enough
     594             :      * byte to cover the whole record header, or at least the part of it that
     595             :      * fits on the same page.
     596             :      */
     597      177718 :     readOff = ReadPageInternal(state, targetPagePtr,
     598      177718 :                                Min(targetRecOff + SizeOfXLogRecord, XLOG_BLCKSZ));
     599      177718 :     if (readOff == XLREAD_WOULDBLOCK)
     600           0 :         return XLREAD_WOULDBLOCK;
     601      177718 :     else if (readOff < 0)
     602           0 :         goto err;
     603             : 
     604             :     /*
     605             :      * ReadPageInternal always returns at least the page header, so we can
     606             :      * examine it now.
     607             :      */
     608      177718 :     pageHeaderSize = XLogPageHeaderSize((XLogPageHeader) state->readBuf);
     609      177718 :     if (targetRecOff == 0)
     610             :     {
     611             :         /*
     612             :          * At page start, so skip over page header.
     613             :          */
     614         188 :         RecPtr += pageHeaderSize;
     615         188 :         targetRecOff = pageHeaderSize;
     616             :     }
     617      177530 :     else if (targetRecOff < pageHeaderSize)
     618             :     {
     619           0 :         report_invalid_record(state, "invalid record offset at %X/%X: expected at least %u, got %u",
     620           0 :                               LSN_FORMAT_ARGS(RecPtr),
     621             :                               pageHeaderSize, targetRecOff);
     622           0 :         goto err;
     623             :     }
     624             : 
     625      177718 :     if ((((XLogPageHeader) state->readBuf)->xlp_info & XLP_FIRST_IS_CONTRECORD) &&
     626             :         targetRecOff == pageHeaderSize)
     627             :     {
     628           0 :         report_invalid_record(state, "contrecord is requested by %X/%X",
     629           0 :                               LSN_FORMAT_ARGS(RecPtr));
     630           0 :         goto err;
     631             :     }
     632             : 
     633             :     /* ReadPageInternal has verified the page header */
     634             :     Assert(pageHeaderSize <= readOff);
     635             : 
     636             :     /*
     637             :      * Read the record length.
     638             :      *
     639             :      * NB: Even though we use an XLogRecord pointer here, the whole record
     640             :      * header might not fit on this page. xl_tot_len is the first field of the
     641             :      * struct, so it must be on this page (the records are MAXALIGNed), but we
     642             :      * cannot access any other fields until we've verified that we got the
     643             :      * whole header.
     644             :      */
     645      177718 :     record = (XLogRecord *) (state->readBuf + RecPtr % XLOG_BLCKSZ);
     646      177718 :     total_len = record->xl_tot_len;
     647             : 
     648             :     /*
     649             :      * If the whole record header is on this page, validate it immediately.
     650             :      * Otherwise do just a basic sanity check on xl_tot_len, and validate the
     651             :      * rest of the header after reading it from the next page.  The xl_tot_len
     652             :      * check is necessary here to ensure that we enter the "Need to reassemble
     653             :      * record" code path below; otherwise we might fail to apply
     654             :      * ValidXLogRecordHeader at all.
     655             :      */
     656      177718 :     if (targetRecOff <= XLOG_BLCKSZ - SizeOfXLogRecord)
     657             :     {
     658      177362 :         if (!ValidXLogRecordHeader(state, RecPtr, state->DecodeRecPtr, record,
     659             :                                    randAccess))
     660           0 :             goto err;
     661      177362 :         gotheader = true;
     662             :     }
     663             :     else
     664             :     {
     665             :         /* There may be no next page if it's too small. */
     666         356 :         if (total_len < SizeOfXLogRecord)
     667             :         {
     668           0 :             report_invalid_record(state,
     669             :                                   "invalid record length at %X/%X: expected at least %u, got %u",
     670           0 :                                   LSN_FORMAT_ARGS(RecPtr),
     671             :                                   (uint32) SizeOfXLogRecord, total_len);
     672           0 :             goto err;
     673             :         }
     674             :         /* We'll validate the header once we have the next page. */
     675         356 :         gotheader = false;
     676             :     }
     677             : 
     678             :     /*
     679             :      * Try to find space to decode this record, if we can do so without
     680             :      * calling palloc.  If we can't, we'll try again below after we've
     681             :      * validated that total_len isn't garbage bytes from a recycled WAL page.
     682             :      */
     683      177718 :     decoded = XLogReadRecordAlloc(state,
     684             :                                   total_len,
     685             :                                   false /* allow_oversized */ );
     686      177718 :     if (decoded == NULL && nonblocking)
     687             :     {
     688             :         /*
     689             :          * There is no space in the circular decode buffer, and the caller is
     690             :          * only reading ahead.  The caller should consume existing records to
     691             :          * make space.
     692             :          */
     693           0 :         return XLREAD_WOULDBLOCK;
     694             :     }
     695             : 
     696      177718 :     len = XLOG_BLCKSZ - RecPtr % XLOG_BLCKSZ;
     697      177718 :     if (total_len > len)
     698             :     {
     699             :         /* Need to reassemble record */
     700             :         char       *contdata;
     701             :         XLogPageHeader pageHeader;
     702             :         char       *buffer;
     703             :         uint32      gotlen;
     704             : 
     705        8468 :         assembled = true;
     706             : 
     707             :         /*
     708             :          * We always have space for a couple of pages, enough to validate a
     709             :          * boundary-spanning record header.
     710             :          */
     711             :         Assert(state->readRecordBufSize >= XLOG_BLCKSZ * 2);
     712             :         Assert(state->readRecordBufSize >= len);
     713             : 
     714             :         /* Copy the first fragment of the record from the first page. */
     715        8468 :         memcpy(state->readRecordBuf,
     716        8468 :                state->readBuf + RecPtr % XLOG_BLCKSZ, len);
     717        8468 :         buffer = state->readRecordBuf + len;
     718        8468 :         gotlen = len;
     719             : 
     720             :         do
     721             :         {
     722             :             /* Calculate pointer to beginning of next page */
     723        8476 :             targetPagePtr += XLOG_BLCKSZ;
     724             : 
     725             :             /* Wait for the next page to become available */
     726        8476 :             readOff = ReadPageInternal(state, targetPagePtr,
     727        8476 :                                        Min(total_len - gotlen + SizeOfXLogShortPHD,
     728             :                                            XLOG_BLCKSZ));
     729             : 
     730        8476 :             if (readOff == XLREAD_WOULDBLOCK)
     731           0 :                 return XLREAD_WOULDBLOCK;
     732        8476 :             else if (readOff < 0)
     733           0 :                 goto err;
     734             : 
     735             :             Assert(SizeOfXLogShortPHD <= readOff);
     736             : 
     737        8476 :             pageHeader = (XLogPageHeader) state->readBuf;
     738             : 
     739             :             /*
     740             :              * If we were expecting a continuation record and got an
     741             :              * "overwrite contrecord" flag, that means the continuation record
     742             :              * was overwritten with a different record.  Restart the read by
     743             :              * assuming the address to read is the location where we found
     744             :              * this flag; but keep track of the LSN of the record we were
     745             :              * reading, for later verification.
     746             :              */
     747        8476 :             if (pageHeader->xlp_info & XLP_FIRST_IS_OVERWRITE_CONTRECORD)
     748             :             {
     749           0 :                 state->overwrittenRecPtr = RecPtr;
     750           0 :                 RecPtr = targetPagePtr;
     751           0 :                 goto restart;
     752             :             }
     753             : 
     754             :             /* Check that the continuation on next page looks valid */
     755        8476 :             if (!(pageHeader->xlp_info & XLP_FIRST_IS_CONTRECORD))
     756             :             {
     757           0 :                 report_invalid_record(state,
     758             :                                       "there is no contrecord flag at %X/%X",
     759           0 :                                       LSN_FORMAT_ARGS(RecPtr));
     760           0 :                 goto err;
     761             :             }
     762             : 
     763             :             /*
     764             :              * Cross-check that xlp_rem_len agrees with how much of the record
     765             :              * we expect there to be left.
     766             :              */
     767        8476 :             if (pageHeader->xlp_rem_len == 0 ||
     768        8476 :                 total_len != (pageHeader->xlp_rem_len + gotlen))
     769             :             {
     770           0 :                 report_invalid_record(state,
     771             :                                       "invalid contrecord length %u (expected %lld) at %X/%X",
     772             :                                       pageHeader->xlp_rem_len,
     773           0 :                                       ((long long) total_len) - gotlen,
     774           0 :                                       LSN_FORMAT_ARGS(RecPtr));
     775           0 :                 goto err;
     776             :             }
     777             : 
     778             :             /* Append the continuation from this page to the buffer */
     779        8476 :             pageHeaderSize = XLogPageHeaderSize(pageHeader);
     780             : 
     781        8476 :             if (readOff < pageHeaderSize)
     782           0 :                 readOff = ReadPageInternal(state, targetPagePtr,
     783             :                                            pageHeaderSize);
     784             : 
     785             :             Assert(pageHeaderSize <= readOff);
     786             : 
     787        8476 :             contdata = (char *) state->readBuf + pageHeaderSize;
     788        8476 :             len = XLOG_BLCKSZ - pageHeaderSize;
     789        8476 :             if (pageHeader->xlp_rem_len < len)
     790        8468 :                 len = pageHeader->xlp_rem_len;
     791             : 
     792        8476 :             if (readOff < pageHeaderSize + len)
     793           0 :                 readOff = ReadPageInternal(state, targetPagePtr,
     794           0 :                                            pageHeaderSize + len);
     795             : 
     796        8476 :             memcpy(buffer, (char *) contdata, len);
     797        8476 :             buffer += len;
     798        8476 :             gotlen += len;
     799             : 
     800             :             /* If we just reassembled the record header, validate it. */
     801        8476 :             if (!gotheader)
     802             :             {
     803         356 :                 record = (XLogRecord *) state->readRecordBuf;
     804         356 :                 if (!ValidXLogRecordHeader(state, RecPtr, state->DecodeRecPtr,
     805             :                                            record, randAccess))
     806           0 :                     goto err;
     807         356 :                 gotheader = true;
     808             :             }
     809             : 
     810             :             /*
     811             :              * We might need a bigger buffer.  We have validated the record
     812             :              * header, in the case that it split over a page boundary.  We've
     813             :              * also cross-checked total_len against xlp_rem_len on the second
     814             :              * page, and verified xlp_pageaddr on both.
     815             :              */
     816        8476 :             if (total_len > state->readRecordBufSize)
     817             :             {
     818             :                 char        save_copy[XLOG_BLCKSZ * 2];
     819             : 
     820             :                 /*
     821             :                  * Save and restore the data we already had.  It can't be more
     822             :                  * than two pages.
     823             :                  */
     824             :                 Assert(gotlen <= lengthof(save_copy));
     825             :                 Assert(gotlen <= state->readRecordBufSize);
     826           0 :                 memcpy(save_copy, state->readRecordBuf, gotlen);
     827           0 :                 allocate_recordbuf(state, total_len);
     828           0 :                 memcpy(state->readRecordBuf, save_copy, gotlen);
     829           0 :                 buffer = state->readRecordBuf + gotlen;
     830             :             }
     831        8476 :         } while (gotlen < total_len);
     832             :         Assert(gotheader);
     833             : 
     834        8468 :         record = (XLogRecord *) state->readRecordBuf;
     835        8468 :         if (!ValidXLogRecord(state, record, RecPtr))
     836           0 :             goto err;
     837             : 
     838        8468 :         pageHeaderSize = XLogPageHeaderSize((XLogPageHeader) state->readBuf);
     839        8468 :         state->DecodeRecPtr = RecPtr;
     840        8468 :         state->NextRecPtr = targetPagePtr + pageHeaderSize
     841        8468 :             + MAXALIGN(pageHeader->xlp_rem_len);
     842             :     }
     843             :     else
     844             :     {
     845             :         /* Wait for the record data to become available */
     846      169250 :         readOff = ReadPageInternal(state, targetPagePtr,
     847      169250 :                                    Min(targetRecOff + total_len, XLOG_BLCKSZ));
     848      169250 :         if (readOff == XLREAD_WOULDBLOCK)
     849           0 :             return XLREAD_WOULDBLOCK;
     850      169250 :         else if (readOff < 0)
     851           0 :             goto err;
     852             : 
     853             :         /* Record does not cross a page boundary */
     854      169250 :         if (!ValidXLogRecord(state, record, RecPtr))
     855           0 :             goto err;
     856             : 
     857      169250 :         state->NextRecPtr = RecPtr + MAXALIGN(total_len);
     858             : 
     859      169250 :         state->DecodeRecPtr = RecPtr;
     860             :     }
     861             : 
     862             :     /*
     863             :      * Special processing if it's an XLOG SWITCH record
     864             :      */
     865      177718 :     if (record->xl_rmid == RM_XLOG_ID &&
     866       11942 :         (record->xl_info & ~XLR_INFO_MASK) == XLOG_SWITCH)
     867             :     {
     868             :         /* Pretend it extends to end of segment */
     869          16 :         state->NextRecPtr += state->segcxt.ws_segsize - 1;
     870          16 :         state->NextRecPtr -= XLogSegmentOffset(state->NextRecPtr, state->segcxt.ws_segsize);
     871             :     }
     872             : 
     873             :     /*
     874             :      * If we got here without a DecodedXLogRecord, it means we needed to
     875             :      * validate total_len before trusting it, but by now we've done that.
     876             :      */
     877      177718 :     if (decoded == NULL)
     878             :     {
     879             :         Assert(!nonblocking);
     880           0 :         decoded = XLogReadRecordAlloc(state,
     881             :                                       total_len,
     882             :                                       true /* allow_oversized */ );
     883             :         /* allocation should always happen under allow_oversized */
     884             :         Assert(decoded != NULL);
     885             :     }
     886             : 
     887      177718 :     if (DecodeXLogRecord(state, decoded, record, RecPtr, &errormsg))
     888             :     {
     889             :         /* Record the location of the next record. */
     890      177718 :         decoded->next_lsn = state->NextRecPtr;
     891             : 
     892             :         /*
     893             :          * If it's in the decode buffer, mark the decode buffer space as
     894             :          * occupied.
     895             :          */
     896      177718 :         if (!decoded->oversized)
     897             :         {
     898             :             /* The new decode buffer head must be MAXALIGNed. */
     899             :             Assert(decoded->size == MAXALIGN(decoded->size));
     900      177718 :             if ((char *) decoded == state->decode_buffer)
     901      177718 :                 state->decode_buffer_tail = state->decode_buffer + decoded->size;
     902             :             else
     903           0 :                 state->decode_buffer_tail += decoded->size;
     904             :         }
     905             : 
     906             :         /* Insert it into the queue of decoded records. */
     907             :         Assert(state->decode_queue_tail != decoded);
     908      177718 :         if (state->decode_queue_tail)
     909           0 :             state->decode_queue_tail->next = decoded;
     910      177718 :         state->decode_queue_tail = decoded;
     911      177718 :         if (!state->decode_queue_head)
     912      177718 :             state->decode_queue_head = decoded;
     913      177718 :         return XLREAD_SUCCESS;
     914             :     }
     915             : 
     916           0 : err:
     917           0 :     if (assembled)
     918             :     {
     919             :         /*
     920             :          * We get here when a record that spans multiple pages needs to be
     921             :          * assembled, but something went wrong -- perhaps a contrecord piece
     922             :          * was lost.  If caller is WAL replay, it will know where the aborted
     923             :          * record was and where to direct followup WAL to be written, marking
     924             :          * the next piece with XLP_FIRST_IS_OVERWRITE_CONTRECORD, which will
     925             :          * in turn signal downstream WAL consumers that the broken WAL record
     926             :          * is to be ignored.
     927             :          */
     928           0 :         state->abortedRecPtr = RecPtr;
     929           0 :         state->missingContrecPtr = targetPagePtr;
     930             : 
     931             :         /*
     932             :          * If we got here without reporting an error, make sure an error is
     933             :          * queued so that XLogPrefetcherReadRecord() doesn't bring us back a
     934             :          * second time and clobber the above state.
     935             :          */
     936           0 :         state->errormsg_deferred = true;
     937             :     }
     938             : 
     939           0 :     if (decoded && decoded->oversized)
     940           0 :         pfree(decoded);
     941             : 
     942             :     /*
     943             :      * Invalidate the read state. We might read from a different source after
     944             :      * failure.
     945             :      */
     946           0 :     XLogReaderInvalReadState(state);
     947             : 
     948             :     /*
     949             :      * If an error was written to errmsg_buf, it'll be returned to the caller
     950             :      * of XLogReadRecord() after all successfully decoded records from the
     951             :      * read queue.
     952             :      */
     953             : 
     954           0 :     return XLREAD_FAIL;
     955             : }
     956             : 
     957             : /*
     958             :  * Try to decode the next available record, and return it.  The record will
     959             :  * also be returned to XLogNextRecord(), which must be called to 'consume'
     960             :  * each record.
     961             :  *
     962             :  * If nonblocking is true, may return NULL due to lack of data or WAL decoding
     963             :  * space.
     964             :  */
     965             : DecodedXLogRecord *
     966      177718 : XLogReadAhead(XLogReaderState *state, bool nonblocking)
     967             : {
     968             :     XLogPageReadResult result;
     969             : 
     970      177718 :     if (state->errormsg_deferred)
     971           0 :         return NULL;
     972             : 
     973      177718 :     result = XLogDecodeNextRecord(state, nonblocking);
     974      177718 :     if (result == XLREAD_SUCCESS)
     975             :     {
     976             :         Assert(state->decode_queue_tail != NULL);
     977      177718 :         return state->decode_queue_tail;
     978             :     }
     979             : 
     980           0 :     return NULL;
     981             : }
     982             : 
     983             : /*
     984             :  * Read a single xlog page including at least [pageptr, reqLen] of valid data
     985             :  * via the page_read() callback.
     986             :  *
     987             :  * Returns XLREAD_FAIL if the required page cannot be read for some
     988             :  * reason; errormsg_buf is set in that case (unless the error occurs in the
     989             :  * page_read callback).
     990             :  *
     991             :  * Returns XLREAD_WOULDBLOCK if the requested data can't be read without
     992             :  * waiting.  This can be returned only if the installed page_read callback
     993             :  * respects the state->nonblocking flag, and cannot read the requested data
     994             :  * immediately.
     995             :  *
     996             :  * We fetch the page from a reader-local cache if we know we have the required
     997             :  * data and if there hasn't been any error since caching the data.
     998             :  */
     999             : static int
    1000      355444 : ReadPageInternal(XLogReaderState *state, XLogRecPtr pageptr, int reqLen)
    1001             : {
    1002             :     int         readLen;
    1003             :     uint32      targetPageOff;
    1004             :     XLogSegNo   targetSegNo;
    1005             :     XLogPageHeader hdr;
    1006             : 
    1007             :     Assert((pageptr % XLOG_BLCKSZ) == 0);
    1008             : 
    1009      355444 :     XLByteToSeg(pageptr, targetSegNo, state->segcxt.ws_segsize);
    1010      355444 :     targetPageOff = XLogSegmentOffset(pageptr, state->segcxt.ws_segsize);
    1011             : 
    1012             :     /* check whether we have all the requested data already */
    1013      355444 :     if (targetSegNo == state->seg.ws_segno &&
    1014      355350 :         targetPageOff == state->segoff && reqLen <= state->readLen)
    1015      344170 :         return state->readLen;
    1016             : 
    1017             :     /*
    1018             :      * Invalidate contents of internal buffer before read attempt.  Just set
    1019             :      * the length to 0, rather than a full XLogReaderInvalReadState(), so we
    1020             :      * don't forget the segment we last successfully read.
    1021             :      */
    1022       11274 :     state->readLen = 0;
    1023             : 
    1024             :     /*
    1025             :      * Data is not in our buffer.
    1026             :      *
    1027             :      * Every time we actually read the segment, even if we looked at parts of
    1028             :      * it before, we need to do verification as the page_read callback might
    1029             :      * now be rereading data from a different source.
    1030             :      *
    1031             :      * Whenever switching to a new WAL segment, we read the first page of the
    1032             :      * file and validate its header, even if that's not where the target
    1033             :      * record is.  This is so that we can check the additional identification
    1034             :      * info that is present in the first page's "long" header.
    1035             :      */
    1036       11274 :     if (targetSegNo != state->seg.ws_segno && targetPageOff != 0)
    1037             :     {
    1038          36 :         XLogRecPtr  targetSegmentPtr = pageptr - targetPageOff;
    1039             : 
    1040          36 :         readLen = state->routine.page_read(state, targetSegmentPtr, XLOG_BLCKSZ,
    1041             :                                            state->currRecPtr,
    1042             :                                            state->readBuf);
    1043          36 :         if (readLen == XLREAD_WOULDBLOCK)
    1044           0 :             return XLREAD_WOULDBLOCK;
    1045          36 :         else if (readLen < 0)
    1046           0 :             goto err;
    1047             : 
    1048             :         /* we can be sure to have enough WAL available, we scrolled back */
    1049             :         Assert(readLen == XLOG_BLCKSZ);
    1050             : 
    1051          36 :         if (!XLogReaderValidatePageHeader(state, targetSegmentPtr,
    1052             :                                           state->readBuf))
    1053           0 :             goto err;
    1054             :     }
    1055             : 
    1056             :     /*
    1057             :      * First, read the requested data length, but at least a short page header
    1058             :      * so that we can validate it.
    1059             :      */
    1060       11274 :     readLen = state->routine.page_read(state, pageptr, Max(reqLen, SizeOfXLogShortPHD),
    1061             :                                        state->currRecPtr,
    1062             :                                        state->readBuf);
    1063       11274 :     if (readLen == XLREAD_WOULDBLOCK)
    1064           0 :         return XLREAD_WOULDBLOCK;
    1065       11274 :     else if (readLen < 0)
    1066           0 :         goto err;
    1067             : 
    1068             :     Assert(readLen <= XLOG_BLCKSZ);
    1069             : 
    1070             :     /* Do we have enough data to check the header length? */
    1071       11274 :     if (readLen <= SizeOfXLogShortPHD)
    1072           0 :         goto err;
    1073             : 
    1074             :     Assert(readLen >= reqLen);
    1075             : 
    1076       11274 :     hdr = (XLogPageHeader) state->readBuf;
    1077             : 
    1078             :     /* still not enough */
    1079       11274 :     if (readLen < XLogPageHeaderSize(hdr))
    1080             :     {
    1081           0 :         readLen = state->routine.page_read(state, pageptr, XLogPageHeaderSize(hdr),
    1082             :                                            state->currRecPtr,
    1083             :                                            state->readBuf);
    1084           0 :         if (readLen == XLREAD_WOULDBLOCK)
    1085           0 :             return XLREAD_WOULDBLOCK;
    1086           0 :         else if (readLen < 0)
    1087           0 :             goto err;
    1088             :     }
    1089             : 
    1090             :     /*
    1091             :      * Now that we know we have the full header, validate it.
    1092             :      */
    1093       11274 :     if (!XLogReaderValidatePageHeader(state, pageptr, (char *) hdr))
    1094           0 :         goto err;
    1095             : 
    1096             :     /* update read state information */
    1097       11274 :     state->seg.ws_segno = targetSegNo;
    1098       11274 :     state->segoff = targetPageOff;
    1099       11274 :     state->readLen = readLen;
    1100             : 
    1101       11274 :     return readLen;
    1102             : 
    1103           0 : err:
    1104           0 :     XLogReaderInvalReadState(state);
    1105             : 
    1106           0 :     return XLREAD_FAIL;
    1107             : }
    1108             : 
    1109             : /*
    1110             :  * Invalidate the xlogreader's read state to force a re-read.
    1111             :  */
    1112             : static void
    1113           0 : XLogReaderInvalReadState(XLogReaderState *state)
    1114             : {
    1115           0 :     state->seg.ws_segno = 0;
    1116           0 :     state->segoff = 0;
    1117           0 :     state->readLen = 0;
    1118           0 : }
    1119             : 
    1120             : /*
    1121             :  * Validate an XLOG record header.
    1122             :  *
    1123             :  * This is just a convenience subroutine to avoid duplicated code in
    1124             :  * XLogReadRecord.  It's not intended for use from anywhere else.
    1125             :  */
    1126             : static bool
    1127      177718 : ValidXLogRecordHeader(XLogReaderState *state, XLogRecPtr RecPtr,
    1128             :                       XLogRecPtr PrevRecPtr, XLogRecord *record,
    1129             :                       bool randAccess)
    1130             : {
    1131      177718 :     if (record->xl_tot_len < SizeOfXLogRecord)
    1132             :     {
    1133           0 :         report_invalid_record(state,
    1134             :                               "invalid record length at %X/%X: expected at least %u, got %u",
    1135           0 :                               LSN_FORMAT_ARGS(RecPtr),
    1136             :                               (uint32) SizeOfXLogRecord, record->xl_tot_len);
    1137           0 :         return false;
    1138             :     }
    1139      177718 :     if (!RmgrIdIsValid(record->xl_rmid))
    1140             :     {
    1141           0 :         report_invalid_record(state,
    1142             :                               "invalid resource manager ID %u at %X/%X",
    1143           0 :                               record->xl_rmid, LSN_FORMAT_ARGS(RecPtr));
    1144           0 :         return false;
    1145             :     }
    1146      177718 :     if (randAccess)
    1147             :     {
    1148             :         /*
    1149             :          * We can't exactly verify the prev-link, but surely it should be less
    1150             :          * than the record's own address.
    1151             :          */
    1152        5148 :         if (!(record->xl_prev < RecPtr))
    1153             :         {
    1154           0 :             report_invalid_record(state,
    1155             :                                   "record with incorrect prev-link %X/%X at %X/%X",
    1156           0 :                                   LSN_FORMAT_ARGS(record->xl_prev),
    1157           0 :                                   LSN_FORMAT_ARGS(RecPtr));
    1158           0 :             return false;
    1159             :         }
    1160             :     }
    1161             :     else
    1162             :     {
    1163             :         /*
    1164             :          * Record's prev-link should exactly match our previous location. This
    1165             :          * check guards against torn WAL pages where a stale but valid-looking
    1166             :          * WAL record starts on a sector boundary.
    1167             :          */
    1168      172570 :         if (record->xl_prev != PrevRecPtr)
    1169             :         {
    1170           0 :             report_invalid_record(state,
    1171             :                                   "record with incorrect prev-link %X/%X at %X/%X",
    1172           0 :                                   LSN_FORMAT_ARGS(record->xl_prev),
    1173           0 :                                   LSN_FORMAT_ARGS(RecPtr));
    1174           0 :             return false;
    1175             :         }
    1176             :     }
    1177             : 
    1178      177718 :     return true;
    1179             : }
    1180             : 
    1181             : 
    1182             : /*
    1183             :  * CRC-check an XLOG record.  We do not believe the contents of an XLOG
    1184             :  * record (other than to the minimal extent of computing the amount of
    1185             :  * data to read in) until we've checked the CRCs.
    1186             :  *
    1187             :  * We assume all of the record (that is, xl_tot_len bytes) has been read
    1188             :  * into memory at *record.  Also, ValidXLogRecordHeader() has accepted the
    1189             :  * record's header, which means in particular that xl_tot_len is at least
    1190             :  * SizeOfXLogRecord.
    1191             :  */
    1192             : static bool
    1193      177718 : ValidXLogRecord(XLogReaderState *state, XLogRecord *record, XLogRecPtr recptr)
    1194             : {
    1195             :     pg_crc32c   crc;
    1196             : 
    1197             :     Assert(record->xl_tot_len >= SizeOfXLogRecord);
    1198             : 
    1199             :     /* Calculate the CRC */
    1200      177718 :     INIT_CRC32C(crc);
    1201      177718 :     COMP_CRC32C(crc, ((char *) record) + SizeOfXLogRecord, record->xl_tot_len - SizeOfXLogRecord);
    1202             :     /* include the record header last */
    1203      177718 :     COMP_CRC32C(crc, (char *) record, offsetof(XLogRecord, xl_crc));
    1204      177718 :     FIN_CRC32C(crc);
    1205             : 
    1206      177718 :     if (!EQ_CRC32C(record->xl_crc, crc))
    1207             :     {
    1208           0 :         report_invalid_record(state,
    1209             :                               "incorrect resource manager data checksum in record at %X/%X",
    1210           0 :                               LSN_FORMAT_ARGS(recptr));
    1211           0 :         return false;
    1212             :     }
    1213             : 
    1214      177718 :     return true;
    1215             : }
    1216             : 
    1217             : /*
    1218             :  * Validate a page header.
    1219             :  *
    1220             :  * Check if 'phdr' is valid as the header of the XLog page at position
    1221             :  * 'recptr'.
    1222             :  */
    1223             : bool
    1224       11310 : XLogReaderValidatePageHeader(XLogReaderState *state, XLogRecPtr recptr,
    1225             :                              char *phdr)
    1226             : {
    1227             :     XLogSegNo   segno;
    1228             :     int32       offset;
    1229       11310 :     XLogPageHeader hdr = (XLogPageHeader) phdr;
    1230             : 
    1231             :     Assert((recptr % XLOG_BLCKSZ) == 0);
    1232             : 
    1233       11310 :     XLByteToSeg(recptr, segno, state->segcxt.ws_segsize);
    1234       11310 :     offset = XLogSegmentOffset(recptr, state->segcxt.ws_segsize);
    1235             : 
    1236       11310 :     if (hdr->xlp_magic != XLOG_PAGE_MAGIC)
    1237             :     {
    1238             :         char        fname[MAXFNAMELEN];
    1239             : 
    1240           0 :         XLogFileName(fname, state->seg.ws_tli, segno, state->segcxt.ws_segsize);
    1241             : 
    1242           0 :         report_invalid_record(state,
    1243             :                               "invalid magic number %04X in WAL segment %s, LSN %X/%X, offset %u",
    1244           0 :                               hdr->xlp_magic,
    1245             :                               fname,
    1246           0 :                               LSN_FORMAT_ARGS(recptr),
    1247             :                               offset);
    1248           0 :         return false;
    1249             :     }
    1250             : 
    1251       11310 :     if ((hdr->xlp_info & ~XLP_ALL_FLAGS) != 0)
    1252             :     {
    1253             :         char        fname[MAXFNAMELEN];
    1254             : 
    1255           0 :         XLogFileName(fname, state->seg.ws_tli, segno, state->segcxt.ws_segsize);
    1256             : 
    1257           0 :         report_invalid_record(state,
    1258             :                               "invalid info bits %04X in WAL segment %s, LSN %X/%X, offset %u",
    1259           0 :                               hdr->xlp_info,
    1260             :                               fname,
    1261           0 :                               LSN_FORMAT_ARGS(recptr),
    1262             :                               offset);
    1263           0 :         return false;
    1264             :     }
    1265             : 
    1266       11310 :     if (hdr->xlp_info & XLP_LONG_HEADER)
    1267             :     {
    1268         106 :         XLogLongPageHeader longhdr = (XLogLongPageHeader) hdr;
    1269             : 
    1270         106 :         if (state->system_identifier &&
    1271           0 :             longhdr->xlp_sysid != state->system_identifier)
    1272             :         {
    1273           0 :             report_invalid_record(state,
    1274             :                                   "WAL file is from different database system: WAL file database system identifier is %llu, pg_control database system identifier is %llu",
    1275           0 :                                   (unsigned long long) longhdr->xlp_sysid,
    1276           0 :                                   (unsigned long long) state->system_identifier);
    1277           0 :             return false;
    1278             :         }
    1279         106 :         else if (longhdr->xlp_seg_size != state->segcxt.ws_segsize)
    1280             :         {
    1281           0 :             report_invalid_record(state,
    1282             :                                   "WAL file is from different database system: incorrect segment size in page header");
    1283           0 :             return false;
    1284             :         }
    1285         106 :         else if (longhdr->xlp_xlog_blcksz != XLOG_BLCKSZ)
    1286             :         {
    1287           0 :             report_invalid_record(state,
    1288             :                                   "WAL file is from different database system: incorrect XLOG_BLCKSZ in page header");
    1289           0 :             return false;
    1290             :         }
    1291             :     }
    1292       11204 :     else if (offset == 0)
    1293             :     {
    1294             :         char        fname[MAXFNAMELEN];
    1295             : 
    1296           0 :         XLogFileName(fname, state->seg.ws_tli, segno, state->segcxt.ws_segsize);
    1297             : 
    1298             :         /* hmm, first page of file doesn't have a long header? */
    1299           0 :         report_invalid_record(state,
    1300             :                               "invalid info bits %04X in WAL segment %s, LSN %X/%X, offset %u",
    1301           0 :                               hdr->xlp_info,
    1302             :                               fname,
    1303           0 :                               LSN_FORMAT_ARGS(recptr),
    1304             :                               offset);
    1305           0 :         return false;
    1306             :     }
    1307             : 
    1308             :     /*
    1309             :      * Check that the address on the page agrees with what we expected. This
    1310             :      * check typically fails when an old WAL segment is recycled, and hasn't
    1311             :      * yet been overwritten with new data yet.
    1312             :      */
    1313       11310 :     if (hdr->xlp_pageaddr != recptr)
    1314             :     {
    1315             :         char        fname[MAXFNAMELEN];
    1316             : 
    1317           0 :         XLogFileName(fname, state->seg.ws_tli, segno, state->segcxt.ws_segsize);
    1318             : 
    1319           0 :         report_invalid_record(state,
    1320             :                               "unexpected pageaddr %X/%X in WAL segment %s, LSN %X/%X, offset %u",
    1321           0 :                               LSN_FORMAT_ARGS(hdr->xlp_pageaddr),
    1322             :                               fname,
    1323           0 :                               LSN_FORMAT_ARGS(recptr),
    1324             :                               offset);
    1325           0 :         return false;
    1326             :     }
    1327             : 
    1328             :     /*
    1329             :      * Since child timelines are always assigned a TLI greater than their
    1330             :      * immediate parent's TLI, we should never see TLI go backwards across
    1331             :      * successive pages of a consistent WAL sequence.
    1332             :      *
    1333             :      * Sometimes we re-read a segment that's already been (partially) read. So
    1334             :      * we only verify TLIs for pages that are later than the last remembered
    1335             :      * LSN.
    1336             :      */
    1337       11310 :     if (recptr > state->latestPagePtr)
    1338             :     {
    1339        8778 :         if (hdr->xlp_tli < state->latestPageTLI)
    1340             :         {
    1341             :             char        fname[MAXFNAMELEN];
    1342             : 
    1343           0 :             XLogFileName(fname, state->seg.ws_tli, segno, state->segcxt.ws_segsize);
    1344             : 
    1345           0 :             report_invalid_record(state,
    1346             :                                   "out-of-sequence timeline ID %u (after %u) in WAL segment %s, LSN %X/%X, offset %u",
    1347             :                                   hdr->xlp_tli,
    1348             :                                   state->latestPageTLI,
    1349             :                                   fname,
    1350           0 :                                   LSN_FORMAT_ARGS(recptr),
    1351             :                                   offset);
    1352           0 :             return false;
    1353             :         }
    1354             :     }
    1355       11310 :     state->latestPagePtr = recptr;
    1356       11310 :     state->latestPageTLI = hdr->xlp_tli;
    1357             : 
    1358       11310 :     return true;
    1359             : }
    1360             : 
    1361             : /*
    1362             :  * Forget about an error produced by XLogReaderValidatePageHeader().
    1363             :  */
    1364             : void
    1365           0 : XLogReaderResetError(XLogReaderState *state)
    1366             : {
    1367           0 :     state->errormsg_buf[0] = '\0';
    1368           0 :     state->errormsg_deferred = false;
    1369           0 : }
    1370             : 
    1371             : /*
    1372             :  * Find the first record with an lsn >= RecPtr.
    1373             :  *
    1374             :  * This is different from XLogBeginRead() in that RecPtr doesn't need to point
    1375             :  * to a valid record boundary.  Useful for checking whether RecPtr is a valid
    1376             :  * xlog address for reading, and to find the first valid address after some
    1377             :  * address when dumping records for debugging purposes.
    1378             :  *
    1379             :  * This positions the reader, like XLogBeginRead(), so that the next call to
    1380             :  * XLogReadRecord() will read the next valid record.
    1381             :  */
    1382             : XLogRecPtr
    1383           0 : XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr)
    1384             : {
    1385             :     XLogRecPtr  tmpRecPtr;
    1386           0 :     XLogRecPtr  found = InvalidXLogRecPtr;
    1387             :     XLogPageHeader header;
    1388             :     char       *errormsg;
    1389             : 
    1390             :     Assert(!XLogRecPtrIsInvalid(RecPtr));
    1391             : 
    1392             :     /* Make sure ReadPageInternal() can't return XLREAD_WOULDBLOCK. */
    1393           0 :     state->nonblocking = false;
    1394             : 
    1395             :     /*
    1396             :      * skip over potential continuation data, keeping in mind that it may span
    1397             :      * multiple pages
    1398             :      */
    1399           0 :     tmpRecPtr = RecPtr;
    1400             :     while (true)
    1401           0 :     {
    1402             :         XLogRecPtr  targetPagePtr;
    1403             :         int         targetRecOff;
    1404             :         uint32      pageHeaderSize;
    1405             :         int         readLen;
    1406             : 
    1407             :         /*
    1408             :          * Compute targetRecOff. It should typically be equal or greater than
    1409             :          * short page-header since a valid record can't start anywhere before
    1410             :          * that, except when caller has explicitly specified the offset that
    1411             :          * falls somewhere there or when we are skipping multi-page
    1412             :          * continuation record. It doesn't matter though because
    1413             :          * ReadPageInternal() is prepared to handle that and will read at
    1414             :          * least short page-header worth of data
    1415             :          */
    1416           0 :         targetRecOff = tmpRecPtr % XLOG_BLCKSZ;
    1417             : 
    1418             :         /* scroll back to page boundary */
    1419           0 :         targetPagePtr = tmpRecPtr - targetRecOff;
    1420             : 
    1421             :         /* Read the page containing the record */
    1422           0 :         readLen = ReadPageInternal(state, targetPagePtr, targetRecOff);
    1423           0 :         if (readLen < 0)
    1424           0 :             goto err;
    1425             : 
    1426           0 :         header = (XLogPageHeader) state->readBuf;
    1427             : 
    1428           0 :         pageHeaderSize = XLogPageHeaderSize(header);
    1429             : 
    1430             :         /* make sure we have enough data for the page header */
    1431           0 :         readLen = ReadPageInternal(state, targetPagePtr, pageHeaderSize);
    1432           0 :         if (readLen < 0)
    1433           0 :             goto err;
    1434             : 
    1435             :         /* skip over potential continuation data */
    1436           0 :         if (header->xlp_info & XLP_FIRST_IS_CONTRECORD)
    1437             :         {
    1438             :             /*
    1439             :              * If the length of the remaining continuation data is more than
    1440             :              * what can fit in this page, the continuation record crosses over
    1441             :              * this page. Read the next page and try again. xlp_rem_len in the
    1442             :              * next page header will contain the remaining length of the
    1443             :              * continuation data
    1444             :              *
    1445             :              * Note that record headers are MAXALIGN'ed
    1446             :              */
    1447           0 :             if (MAXALIGN(header->xlp_rem_len) >= (XLOG_BLCKSZ - pageHeaderSize))
    1448           0 :                 tmpRecPtr = targetPagePtr + XLOG_BLCKSZ;
    1449             :             else
    1450             :             {
    1451             :                 /*
    1452             :                  * The previous continuation record ends in this page. Set
    1453             :                  * tmpRecPtr to point to the first valid record
    1454             :                  */
    1455           0 :                 tmpRecPtr = targetPagePtr + pageHeaderSize
    1456           0 :                     + MAXALIGN(header->xlp_rem_len);
    1457           0 :                 break;
    1458             :             }
    1459             :         }
    1460             :         else
    1461             :         {
    1462           0 :             tmpRecPtr = targetPagePtr + pageHeaderSize;
    1463           0 :             break;
    1464             :         }
    1465             :     }
    1466             : 
    1467             :     /*
    1468             :      * we know now that tmpRecPtr is an address pointing to a valid XLogRecord
    1469             :      * because either we're at the first record after the beginning of a page
    1470             :      * or we just jumped over the remaining data of a continuation.
    1471             :      */
    1472           0 :     XLogBeginRead(state, tmpRecPtr);
    1473           0 :     while (XLogReadRecord(state, &errormsg) != NULL)
    1474             :     {
    1475             :         /* past the record we've found, break out */
    1476           0 :         if (RecPtr <= state->ReadRecPtr)
    1477             :         {
    1478             :             /* Rewind the reader to the beginning of the last record. */
    1479           0 :             found = state->ReadRecPtr;
    1480           0 :             XLogBeginRead(state, found);
    1481           0 :             return found;
    1482             :         }
    1483             :     }
    1484             : 
    1485           0 : err:
    1486           0 :     XLogReaderInvalReadState(state);
    1487             : 
    1488           0 :     return InvalidXLogRecPtr;
    1489             : }
    1490             : 
    1491             : /*
    1492             :  * Helper function to ease writing of XLogReaderRoutine->page_read callbacks.
    1493             :  * If this function is used, caller must supply a segment_open callback in
    1494             :  * 'state', as that is used here.
    1495             :  *
    1496             :  * Read 'count' bytes into 'buf', starting at location 'startptr', from WAL
    1497             :  * fetched from timeline 'tli'.
    1498             :  *
    1499             :  * Returns true if succeeded, false if an error occurs, in which case
    1500             :  * 'errinfo' receives error details.
    1501             :  */
    1502             : bool
    1503           0 : WALRead(XLogReaderState *state,
    1504             :         char *buf, XLogRecPtr startptr, Size count, TimeLineID tli,
    1505             :         WALReadError *errinfo)
    1506             : {
    1507             :     char       *p;
    1508             :     XLogRecPtr  recptr;
    1509             :     Size        nbytes;
    1510             : 
    1511           0 :     p = buf;
    1512           0 :     recptr = startptr;
    1513           0 :     nbytes = count;
    1514             : 
    1515           0 :     while (nbytes > 0)
    1516             :     {
    1517             :         uint32      startoff;
    1518             :         int         segbytes;
    1519             :         int         readbytes;
    1520             : 
    1521           0 :         startoff = XLogSegmentOffset(recptr, state->segcxt.ws_segsize);
    1522             : 
    1523             :         /*
    1524             :          * If the data we want is not in a segment we have open, close what we
    1525             :          * have (if anything) and open the next one, using the caller's
    1526             :          * provided segment_open callback.
    1527             :          */
    1528           0 :         if (state->seg.ws_file < 0 ||
    1529           0 :             !XLByteInSeg(recptr, state->seg.ws_segno, state->segcxt.ws_segsize) ||
    1530           0 :             tli != state->seg.ws_tli)
    1531             :         {
    1532             :             XLogSegNo   nextSegNo;
    1533             : 
    1534           0 :             if (state->seg.ws_file >= 0)
    1535           0 :                 state->routine.segment_close(state);
    1536             : 
    1537           0 :             XLByteToSeg(recptr, nextSegNo, state->segcxt.ws_segsize);
    1538           0 :             state->routine.segment_open(state, nextSegNo, &tli);
    1539             : 
    1540             :             /* This shouldn't happen -- indicates a bug in segment_open */
    1541             :             Assert(state->seg.ws_file >= 0);
    1542             : 
    1543             :             /* Update the current segment info. */
    1544           0 :             state->seg.ws_tli = tli;
    1545           0 :             state->seg.ws_segno = nextSegNo;
    1546             :         }
    1547             : 
    1548             :         /* How many bytes are within this segment? */
    1549           0 :         if (nbytes > (state->segcxt.ws_segsize - startoff))
    1550           0 :             segbytes = state->segcxt.ws_segsize - startoff;
    1551             :         else
    1552           0 :             segbytes = nbytes;
    1553             : 
    1554             : #ifndef FRONTEND
    1555             :         pgstat_report_wait_start(WAIT_EVENT_WAL_READ);
    1556             : #endif
    1557             : 
    1558             :         /* Reset errno first; eases reporting non-errno-affecting errors */
    1559           0 :         errno = 0;
    1560           0 :         readbytes = pg_pread(state->seg.ws_file, p, segbytes, (off_t) startoff);
    1561             : 
    1562             : #ifndef FRONTEND
    1563             :         pgstat_report_wait_end();
    1564             : #endif
    1565             : 
    1566           0 :         if (readbytes <= 0)
    1567             :         {
    1568           0 :             errinfo->wre_errno = errno;
    1569           0 :             errinfo->wre_req = segbytes;
    1570           0 :             errinfo->wre_read = readbytes;
    1571           0 :             errinfo->wre_off = startoff;
    1572           0 :             errinfo->wre_seg = state->seg;
    1573           0 :             return false;
    1574             :         }
    1575             : 
    1576             :         /* Update state for read */
    1577           0 :         recptr += readbytes;
    1578           0 :         nbytes -= readbytes;
    1579           0 :         p += readbytes;
    1580             :     }
    1581             : 
    1582           0 :     return true;
    1583             : }
    1584             : 
    1585             : /* ----------------------------------------
    1586             :  * Functions for decoding the data and block references in a record.
    1587             :  * ----------------------------------------
    1588             :  */
    1589             : 
    1590             : /*
    1591             :  * Private function to reset the state, forgetting all decoded records, if we
    1592             :  * are asked to move to a new read position.
    1593             :  */
    1594             : static void
    1595        5148 : ResetDecoder(XLogReaderState *state)
    1596             : {
    1597             :     DecodedXLogRecord *r;
    1598             : 
    1599             :     /* Reset the decoded record queue, freeing any oversized records. */
    1600       10218 :     while ((r = state->decode_queue_head) != NULL)
    1601             :     {
    1602        5070 :         state->decode_queue_head = r->next;
    1603        5070 :         if (r->oversized)
    1604           0 :             pfree(r);
    1605             :     }
    1606        5148 :     state->decode_queue_tail = NULL;
    1607        5148 :     state->decode_queue_head = NULL;
    1608        5148 :     state->record = NULL;
    1609             : 
    1610             :     /* Reset the decode buffer to empty. */
    1611        5148 :     state->decode_buffer_tail = state->decode_buffer;
    1612        5148 :     state->decode_buffer_head = state->decode_buffer;
    1613             : 
    1614             :     /* Clear error state. */
    1615        5148 :     state->errormsg_buf[0] = '\0';
    1616        5148 :     state->errormsg_deferred = false;
    1617        5148 : }
    1618             : 
    1619             : /*
    1620             :  * Compute the maximum possible amount of padding that could be required to
    1621             :  * decode a record, given xl_tot_len from the record's header.  This is the
    1622             :  * amount of output buffer space that we need to decode a record, though we
    1623             :  * might not finish up using it all.
    1624             :  *
    1625             :  * This computation is pessimistic and assumes the maximum possible number of
    1626             :  * blocks, due to lack of better information.
    1627             :  */
    1628             : size_t
    1629      177718 : DecodeXLogRecordRequiredSpace(size_t xl_tot_len)
    1630             : {
    1631      177718 :     size_t      size = 0;
    1632             : 
    1633             :     /* Account for the fixed size part of the decoded record struct. */
    1634      177718 :     size += offsetof(DecodedXLogRecord, blocks[0]);
    1635             :     /* Account for the flexible blocks array of maximum possible size. */
    1636      177718 :     size += sizeof(DecodedBkpBlock) * (XLR_MAX_BLOCK_ID + 1);
    1637             :     /* Account for all the raw main and block data. */
    1638      177718 :     size += xl_tot_len;
    1639             :     /* We might insert padding before main_data. */
    1640      177718 :     size += (MAXIMUM_ALIGNOF - 1);
    1641             :     /* We might insert padding before each block's data. */
    1642      177718 :     size += (MAXIMUM_ALIGNOF - 1) * (XLR_MAX_BLOCK_ID + 1);
    1643             :     /* We might insert padding at the end. */
    1644      177718 :     size += (MAXIMUM_ALIGNOF - 1);
    1645             : 
    1646      177718 :     return size;
    1647             : }
    1648             : 
    1649             : /*
    1650             :  * Decode a record.  "decoded" must point to a MAXALIGNed memory area that has
    1651             :  * space for at least DecodeXLogRecordRequiredSpace(record) bytes.  On
    1652             :  * success, decoded->size contains the actual space occupied by the decoded
    1653             :  * record, which may turn out to be less.
    1654             :  *
    1655             :  * Only decoded->oversized member must be initialized already, and will not be
    1656             :  * modified.  Other members will be initialized as required.
    1657             :  *
    1658             :  * On error, a human-readable error message is returned in *errormsg, and
    1659             :  * the return value is false.
    1660             :  */
    1661             : bool
    1662      177718 : DecodeXLogRecord(XLogReaderState *state,
    1663             :                  DecodedXLogRecord *decoded,
    1664             :                  XLogRecord *record,
    1665             :                  XLogRecPtr lsn,
    1666             :                  char **errormsg)
    1667             : {
    1668             :     /*
    1669             :      * read next _size bytes from record buffer, but check for overrun first.
    1670             :      */
    1671             : #define COPY_HEADER_FIELD(_dst, _size)          \
    1672             :     do {                                        \
    1673             :         if (remaining < _size)                   \
    1674             :             goto shortdata_err;                 \
    1675             :         memcpy(_dst, ptr, _size);               \
    1676             :         ptr += _size;                           \
    1677             :         remaining -= _size;                     \
    1678             :     } while(0)
    1679             : 
    1680             :     char       *ptr;
    1681             :     char       *out;
    1682             :     uint32      remaining;
    1683             :     uint32      datatotal;
    1684      177718 :     RelFileLocator *rlocator = NULL;
    1685             :     uint8       block_id;
    1686             : 
    1687      177718 :     decoded->header = *record;
    1688      177718 :     decoded->lsn = lsn;
    1689      177718 :     decoded->next = NULL;
    1690      177718 :     decoded->record_origin = InvalidRepOriginId;
    1691      177718 :     decoded->toplevel_xid = InvalidTransactionId;
    1692      177718 :     decoded->main_data = NULL;
    1693      177718 :     decoded->main_data_len = 0;
    1694      177718 :     decoded->max_block_id = -1;
    1695      177718 :     ptr = (char *) record;
    1696      177718 :     ptr += SizeOfXLogRecord;
    1697      177718 :     remaining = record->xl_tot_len - SizeOfXLogRecord;
    1698             : 
    1699             :     /* Decode the headers */
    1700      177718 :     datatotal = 0;
    1701      352228 :     while (remaining > datatotal)
    1702             :     {
    1703      340434 :         COPY_HEADER_FIELD(&block_id, sizeof(uint8));
    1704             : 
    1705      340434 :         if (block_id == XLR_BLOCK_ID_DATA_SHORT)
    1706             :         {
    1707             :             /* XLogRecordDataHeaderShort */
    1708             :             uint8       main_data_len;
    1709             : 
    1710      165892 :             COPY_HEADER_FIELD(&main_data_len, sizeof(uint8));
    1711             : 
    1712      165892 :             decoded->main_data_len = main_data_len;
    1713      165892 :             datatotal += main_data_len;
    1714      165892 :             break;              /* by convention, the main data fragment is
    1715             :                                  * always last */
    1716             :         }
    1717      174542 :         else if (block_id == XLR_BLOCK_ID_DATA_LONG)
    1718             :         {
    1719             :             /* XLogRecordDataHeaderLong */
    1720             :             uint32      main_data_len;
    1721             : 
    1722          32 :             COPY_HEADER_FIELD(&main_data_len, sizeof(uint32));
    1723          32 :             decoded->main_data_len = main_data_len;
    1724          32 :             datatotal += main_data_len;
    1725          32 :             break;              /* by convention, the main data fragment is
    1726             :                                  * always last */
    1727             :         }
    1728      174510 :         else if (block_id == XLR_BLOCK_ID_ORIGIN)
    1729             :         {
    1730           0 :             COPY_HEADER_FIELD(&decoded->record_origin, sizeof(RepOriginId));
    1731             :         }
    1732      174510 :         else if (block_id == XLR_BLOCK_ID_TOPLEVEL_XID)
    1733             :         {
    1734           0 :             COPY_HEADER_FIELD(&decoded->toplevel_xid, sizeof(TransactionId));
    1735             :         }
    1736      174510 :         else if (block_id <= XLR_MAX_BLOCK_ID)
    1737             :         {
    1738             :             /* XLogRecordBlockHeader */
    1739             :             DecodedBkpBlock *blk;
    1740             :             uint8       fork_flags;
    1741             : 
    1742             :             /* mark any intervening block IDs as not in use */
    1743      174510 :             for (int i = decoded->max_block_id + 1; i < block_id; ++i)
    1744           0 :                 decoded->blocks[i].in_use = false;
    1745             : 
    1746      174510 :             if (block_id <= decoded->max_block_id)
    1747             :             {
    1748           0 :                 report_invalid_record(state,
    1749             :                                       "out-of-order block_id %u at %X/%X",
    1750             :                                       block_id,
    1751           0 :                                       LSN_FORMAT_ARGS(state->ReadRecPtr));
    1752           0 :                 goto err;
    1753             :             }
    1754      174510 :             decoded->max_block_id = block_id;
    1755             : 
    1756      174510 :             blk = &decoded->blocks[block_id];
    1757      174510 :             blk->in_use = true;
    1758      174510 :             blk->apply_image = false;
    1759             : 
    1760      174510 :             COPY_HEADER_FIELD(&fork_flags, sizeof(uint8));
    1761      174510 :             blk->forknum = fork_flags & BKPBLOCK_FORK_MASK;
    1762      174510 :             blk->flags = fork_flags;
    1763      174510 :             blk->has_image = ((fork_flags & BKPBLOCK_HAS_IMAGE) != 0);
    1764      174510 :             blk->has_data = ((fork_flags & BKPBLOCK_HAS_DATA) != 0);
    1765             : 
    1766      174510 :             blk->prefetch_buffer = InvalidBuffer;
    1767             : 
    1768      174510 :             COPY_HEADER_FIELD(&blk->data_len, sizeof(uint16));
    1769             :             /* cross-check that the HAS_DATA flag is set iff data_length > 0 */
    1770      174510 :             if (blk->has_data && blk->data_len == 0)
    1771             :             {
    1772           0 :                 report_invalid_record(state,
    1773             :                                       "BKPBLOCK_HAS_DATA set, but no data included at %X/%X",
    1774           0 :                                       LSN_FORMAT_ARGS(state->ReadRecPtr));
    1775           0 :                 goto err;
    1776             :             }
    1777      174510 :             if (!blk->has_data && blk->data_len != 0)
    1778             :             {
    1779           0 :                 report_invalid_record(state,
    1780             :                                       "BKPBLOCK_HAS_DATA not set, but data length is %u at %X/%X",
    1781           0 :                                       (unsigned int) blk->data_len,
    1782           0 :                                       LSN_FORMAT_ARGS(state->ReadRecPtr));
    1783           0 :                 goto err;
    1784             :             }
    1785      174510 :             datatotal += blk->data_len;
    1786             : 
    1787      174510 :             if (blk->has_image)
    1788             :             {
    1789       11874 :                 COPY_HEADER_FIELD(&blk->bimg_len, sizeof(uint16));
    1790       11874 :                 COPY_HEADER_FIELD(&blk->hole_offset, sizeof(uint16));
    1791       11874 :                 COPY_HEADER_FIELD(&blk->bimg_info, sizeof(uint8));
    1792             : 
    1793       11874 :                 blk->apply_image = ((blk->bimg_info & BKPIMAGE_APPLY) != 0);
    1794             : 
    1795       11874 :                 if (BKPIMAGE_COMPRESSED(blk->bimg_info))
    1796             :                 {
    1797           0 :                     if (blk->bimg_info & BKPIMAGE_HAS_HOLE)
    1798           0 :                         COPY_HEADER_FIELD(&blk->hole_length, sizeof(uint16));
    1799             :                     else
    1800           0 :                         blk->hole_length = 0;
    1801             :                 }
    1802             :                 else
    1803       11874 :                     blk->hole_length = BLCKSZ - blk->bimg_len;
    1804       11874 :                 datatotal += blk->bimg_len;
    1805             : 
    1806             :                 /*
    1807             :                  * cross-check that hole_offset > 0, hole_length > 0 and
    1808             :                  * bimg_len < BLCKSZ if the HAS_HOLE flag is set.
    1809             :                  */
    1810       11874 :                 if ((blk->bimg_info & BKPIMAGE_HAS_HOLE) &&
    1811       11742 :                     (blk->hole_offset == 0 ||
    1812       11742 :                      blk->hole_length == 0 ||
    1813       11742 :                      blk->bimg_len == BLCKSZ))
    1814             :                 {
    1815           0 :                     report_invalid_record(state,
    1816             :                                           "BKPIMAGE_HAS_HOLE set, but hole offset %u length %u block image length %u at %X/%X",
    1817           0 :                                           (unsigned int) blk->hole_offset,
    1818           0 :                                           (unsigned int) blk->hole_length,
    1819           0 :                                           (unsigned int) blk->bimg_len,
    1820           0 :                                           LSN_FORMAT_ARGS(state->ReadRecPtr));
    1821           0 :                     goto err;
    1822             :                 }
    1823             : 
    1824             :                 /*
    1825             :                  * cross-check that hole_offset == 0 and hole_length == 0 if
    1826             :                  * the HAS_HOLE flag is not set.
    1827             :                  */
    1828       11874 :                 if (!(blk->bimg_info & BKPIMAGE_HAS_HOLE) &&
    1829         132 :                     (blk->hole_offset != 0 || blk->hole_length != 0))
    1830             :                 {
    1831           0 :                     report_invalid_record(state,
    1832             :                                           "BKPIMAGE_HAS_HOLE not set, but hole offset %u length %u at %X/%X",
    1833           0 :                                           (unsigned int) blk->hole_offset,
    1834           0 :                                           (unsigned int) blk->hole_length,
    1835           0 :                                           LSN_FORMAT_ARGS(state->ReadRecPtr));
    1836           0 :                     goto err;
    1837             :                 }
    1838             : 
    1839             :                 /*
    1840             :                  * Cross-check that bimg_len < BLCKSZ if it is compressed.
    1841             :                  */
    1842       11874 :                 if (BKPIMAGE_COMPRESSED(blk->bimg_info) &&
    1843           0 :                     blk->bimg_len == BLCKSZ)
    1844             :                 {
    1845           0 :                     report_invalid_record(state,
    1846             :                                           "BKPIMAGE_COMPRESSED set, but block image length %u at %X/%X",
    1847           0 :                                           (unsigned int) blk->bimg_len,
    1848           0 :                                           LSN_FORMAT_ARGS(state->ReadRecPtr));
    1849           0 :                     goto err;
    1850             :                 }
    1851             : 
    1852             :                 /*
    1853             :                  * cross-check that bimg_len = BLCKSZ if neither HAS_HOLE is
    1854             :                  * set nor COMPRESSED().
    1855             :                  */
    1856       11874 :                 if (!(blk->bimg_info & BKPIMAGE_HAS_HOLE) &&
    1857         132 :                     !BKPIMAGE_COMPRESSED(blk->bimg_info) &&
    1858         132 :                     blk->bimg_len != BLCKSZ)
    1859             :                 {
    1860           0 :                     report_invalid_record(state,
    1861             :                                           "neither BKPIMAGE_HAS_HOLE nor BKPIMAGE_COMPRESSED set, but block image length is %u at %X/%X",
    1862           0 :                                           (unsigned int) blk->data_len,
    1863           0 :                                           LSN_FORMAT_ARGS(state->ReadRecPtr));
    1864           0 :                     goto err;
    1865             :                 }
    1866             :             }
    1867      174510 :             if (!(fork_flags & BKPBLOCK_SAME_REL))
    1868             :             {
    1869      173814 :                 COPY_HEADER_FIELD(&blk->rlocator, sizeof(RelFileLocator));
    1870      173814 :                 rlocator = &blk->rlocator;
    1871             :             }
    1872             :             else
    1873             :             {
    1874         696 :                 if (rlocator == NULL)
    1875             :                 {
    1876           0 :                     report_invalid_record(state,
    1877             :                                           "BKPBLOCK_SAME_REL set but no previous rel at %X/%X",
    1878           0 :                                           LSN_FORMAT_ARGS(state->ReadRecPtr));
    1879           0 :                     goto err;
    1880             :                 }
    1881             : 
    1882         696 :                 blk->rlocator = *rlocator;
    1883             :             }
    1884      174510 :             COPY_HEADER_FIELD(&blk->blkno, sizeof(BlockNumber));
    1885             :         }
    1886             :         else
    1887             :         {
    1888           0 :             report_invalid_record(state,
    1889             :                                   "invalid block_id %u at %X/%X",
    1890           0 :                                   block_id, LSN_FORMAT_ARGS(state->ReadRecPtr));
    1891           0 :             goto err;
    1892             :         }
    1893             :     }
    1894             : 
    1895      177718 :     if (remaining != datatotal)
    1896           0 :         goto shortdata_err;
    1897             : 
    1898             :     /*
    1899             :      * Ok, we've parsed the fragment headers, and verified that the total
    1900             :      * length of the payload in the fragments is equal to the amount of data
    1901             :      * left.  Copy the data of each fragment to contiguous space after the
    1902             :      * blocks array, inserting alignment padding before the data fragments so
    1903             :      * they can be cast to struct pointers by REDO routines.
    1904             :      */
    1905      177718 :     out = ((char *) decoded) +
    1906      177718 :         offsetof(DecodedXLogRecord, blocks) +
    1907      177718 :         sizeof(decoded->blocks[0]) * (decoded->max_block_id + 1);
    1908             : 
    1909             :     /* block data first */
    1910      352228 :     for (block_id = 0; block_id <= decoded->max_block_id; block_id++)
    1911             :     {
    1912      174510 :         DecodedBkpBlock *blk = &decoded->blocks[block_id];
    1913             : 
    1914      174510 :         if (!blk->in_use)
    1915           0 :             continue;
    1916             : 
    1917             :         Assert(blk->has_image || !blk->apply_image);
    1918             : 
    1919      174510 :         if (blk->has_image)
    1920             :         {
    1921             :             /* no need to align image */
    1922       11874 :             blk->bkp_image = out;
    1923       11874 :             memcpy(out, ptr, blk->bimg_len);
    1924       11874 :             ptr += blk->bimg_len;
    1925       11874 :             out += blk->bimg_len;
    1926             :         }
    1927      174510 :         if (blk->has_data)
    1928             :         {
    1929       81124 :             out = (char *) MAXALIGN(out);
    1930       81124 :             blk->data = out;
    1931       81124 :             memcpy(blk->data, ptr, blk->data_len);
    1932       81124 :             ptr += blk->data_len;
    1933       81124 :             out += blk->data_len;
    1934             :         }
    1935             :     }
    1936             : 
    1937             :     /* and finally, the main data */
    1938      177718 :     if (decoded->main_data_len > 0)
    1939             :     {
    1940      165924 :         out = (char *) MAXALIGN(out);
    1941      165924 :         decoded->main_data = out;
    1942      165924 :         memcpy(decoded->main_data, ptr, decoded->main_data_len);
    1943      165924 :         ptr += decoded->main_data_len;
    1944      165924 :         out += decoded->main_data_len;
    1945             :     }
    1946             : 
    1947             :     /* Report the actual size we used. */
    1948      177718 :     decoded->size = MAXALIGN(out - (char *) decoded);
    1949             :     Assert(DecodeXLogRecordRequiredSpace(record->xl_tot_len) >=
    1950             :            decoded->size);
    1951             : 
    1952      177718 :     return true;
    1953             : 
    1954           0 : shortdata_err:
    1955           0 :     report_invalid_record(state,
    1956             :                           "record with invalid length at %X/%X",
    1957           0 :                           LSN_FORMAT_ARGS(state->ReadRecPtr));
    1958           0 : err:
    1959           0 :     *errormsg = state->errormsg_buf;
    1960             : 
    1961           0 :     return false;
    1962             : }
    1963             : 
    1964             : /*
    1965             :  * Returns information about the block that a block reference refers to.
    1966             :  *
    1967             :  * This is like XLogRecGetBlockTagExtended, except that the block reference
    1968             :  * must exist and there's no access to prefetch_buffer.
    1969             :  */
    1970             : void
    1971           0 : XLogRecGetBlockTag(XLogReaderState *record, uint8 block_id,
    1972             :                    RelFileLocator *rlocator, ForkNumber *forknum,
    1973             :                    BlockNumber *blknum)
    1974             : {
    1975           0 :     if (!XLogRecGetBlockTagExtended(record, block_id, rlocator, forknum,
    1976             :                                     blknum, NULL))
    1977             :     {
    1978             : #ifndef FRONTEND
    1979             :         elog(ERROR, "could not locate backup block with ID %d in WAL record",
    1980             :              block_id);
    1981             : #else
    1982           0 :         pg_fatal("could not locate backup block with ID %d in WAL record",
    1983             :                  block_id);
    1984             : #endif
    1985             :     }
    1986           0 : }
    1987             : 
    1988             : /*
    1989             :  * Returns information about the block that a block reference refers to,
    1990             :  * optionally including the buffer that the block may already be in.
    1991             :  *
    1992             :  * If the WAL record contains a block reference with the given ID, *rlocator,
    1993             :  * *forknum, *blknum and *prefetch_buffer are filled in (if not NULL), and
    1994             :  * returns true.  Otherwise returns false.
    1995             :  */
    1996             : bool
    1997      170658 : XLogRecGetBlockTagExtended(XLogReaderState *record, uint8 block_id,
    1998             :                            RelFileLocator *rlocator, ForkNumber *forknum,
    1999             :                            BlockNumber *blknum,
    2000             :                            Buffer *prefetch_buffer)
    2001             : {
    2002             :     DecodedBkpBlock *bkpb;
    2003             : 
    2004      170658 :     if (!XLogRecHasBlockRef(record, block_id))
    2005           0 :         return false;
    2006             : 
    2007      170658 :     bkpb = &record->record->blocks[block_id];
    2008      170658 :     if (rlocator)
    2009      170658 :         *rlocator = bkpb->rlocator;
    2010      170658 :     if (forknum)
    2011      170658 :         *forknum = bkpb->forknum;
    2012      170658 :     if (blknum)
    2013      170658 :         *blknum = bkpb->blkno;
    2014      170658 :     if (prefetch_buffer)
    2015           0 :         *prefetch_buffer = bkpb->prefetch_buffer;
    2016      170658 :     return true;
    2017             : }
    2018             : 
    2019             : /*
    2020             :  * Returns the data associated with a block reference, or NULL if there is
    2021             :  * no data (e.g. because a full-page image was taken instead). The returned
    2022             :  * pointer points to a MAXALIGNed buffer.
    2023             :  */
    2024             : char *
    2025           0 : XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
    2026             : {
    2027             :     DecodedBkpBlock *bkpb;
    2028             : 
    2029           0 :     if (block_id > record->record->max_block_id ||
    2030           0 :         !record->record->blocks[block_id].in_use)
    2031           0 :         return NULL;
    2032             : 
    2033           0 :     bkpb = &record->record->blocks[block_id];
    2034             : 
    2035           0 :     if (!bkpb->has_data)
    2036             :     {
    2037           0 :         if (len)
    2038           0 :             *len = 0;
    2039           0 :         return NULL;
    2040             :     }
    2041             :     else
    2042             :     {
    2043           0 :         if (len)
    2044           0 :             *len = bkpb->data_len;
    2045           0 :         return bkpb->data;
    2046             :     }
    2047             : }
    2048             : 
    2049             : /*
    2050             :  * Restore a full-page image from a backup block attached to an XLOG record.
    2051             :  *
    2052             :  * Returns true if a full-page image is restored, and false on failure with
    2053             :  * an error to be consumed by the caller.
    2054             :  */
    2055             : bool
    2056           0 : RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
    2057             : {
    2058             :     DecodedBkpBlock *bkpb;
    2059             :     char       *ptr;
    2060             :     PGAlignedBlock tmp;
    2061             : 
    2062           0 :     if (block_id > record->record->max_block_id ||
    2063           0 :         !record->record->blocks[block_id].in_use)
    2064             :     {
    2065           0 :         report_invalid_record(record,
    2066             :                               "could not restore image at %X/%X with invalid block %d specified",
    2067           0 :                               LSN_FORMAT_ARGS(record->ReadRecPtr),
    2068             :                               block_id);
    2069           0 :         return false;
    2070             :     }
    2071           0 :     if (!record->record->blocks[block_id].has_image)
    2072             :     {
    2073           0 :         report_invalid_record(record, "could not restore image at %X/%X with invalid state, block %d",
    2074           0 :                               LSN_FORMAT_ARGS(record->ReadRecPtr),
    2075             :                               block_id);
    2076           0 :         return false;
    2077             :     }
    2078             : 
    2079           0 :     bkpb = &record->record->blocks[block_id];
    2080           0 :     ptr = bkpb->bkp_image;
    2081             : 
    2082           0 :     if (BKPIMAGE_COMPRESSED(bkpb->bimg_info))
    2083             :     {
    2084             :         /* If a backup block image is compressed, decompress it */
    2085           0 :         bool        decomp_success = true;
    2086             : 
    2087           0 :         if ((bkpb->bimg_info & BKPIMAGE_COMPRESS_PGLZ) != 0)
    2088             :         {
    2089           0 :             if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
    2090           0 :                                 BLCKSZ - bkpb->hole_length, true) < 0)
    2091           0 :                 decomp_success = false;
    2092             :         }
    2093           0 :         else if ((bkpb->bimg_info & BKPIMAGE_COMPRESS_LZ4) != 0)
    2094             :         {
    2095             : #ifdef USE_LZ4
    2096           0 :             if (LZ4_decompress_safe(ptr, tmp.data,
    2097           0 :                                     bkpb->bimg_len, BLCKSZ - bkpb->hole_length) <= 0)
    2098           0 :                 decomp_success = false;
    2099             : #else
    2100             :             report_invalid_record(record, "could not restore image at %X/%X compressed with %s not supported by build, block %d",
    2101             :                                   LSN_FORMAT_ARGS(record->ReadRecPtr),
    2102             :                                   "LZ4",
    2103             :                                   block_id);
    2104             :             return false;
    2105             : #endif
    2106             :         }
    2107           0 :         else if ((bkpb->bimg_info & BKPIMAGE_COMPRESS_ZSTD) != 0)
    2108             :         {
    2109             : #ifdef USE_ZSTD
    2110             :             size_t      decomp_result = ZSTD_decompress(tmp.data,
    2111             :                                                         BLCKSZ - bkpb->hole_length,
    2112             :                                                         ptr, bkpb->bimg_len);
    2113             : 
    2114             :             if (ZSTD_isError(decomp_result))
    2115             :                 decomp_success = false;
    2116             : #else
    2117           0 :             report_invalid_record(record, "could not restore image at %X/%X compressed with %s not supported by build, block %d",
    2118           0 :                                   LSN_FORMAT_ARGS(record->ReadRecPtr),
    2119             :                                   "zstd",
    2120             :                                   block_id);
    2121           0 :             return false;
    2122             : #endif
    2123             :         }
    2124             :         else
    2125             :         {
    2126           0 :             report_invalid_record(record, "could not restore image at %X/%X compressed with unknown method, block %d",
    2127           0 :                                   LSN_FORMAT_ARGS(record->ReadRecPtr),
    2128             :                                   block_id);
    2129           0 :             return false;
    2130             :         }
    2131             : 
    2132           0 :         if (!decomp_success)
    2133             :         {
    2134           0 :             report_invalid_record(record, "could not decompress image at %X/%X, block %d",
    2135           0 :                                   LSN_FORMAT_ARGS(record->ReadRecPtr),
    2136             :                                   block_id);
    2137           0 :             return false;
    2138             :         }
    2139             : 
    2140           0 :         ptr = tmp.data;
    2141             :     }
    2142             : 
    2143             :     /* generate page, taking into account hole if necessary */
    2144           0 :     if (bkpb->hole_length == 0)
    2145             :     {
    2146           0 :         memcpy(page, ptr, BLCKSZ);
    2147             :     }
    2148             :     else
    2149             :     {
    2150           0 :         memcpy(page, ptr, bkpb->hole_offset);
    2151             :         /* must zero-fill the hole */
    2152           0 :         MemSet(page + bkpb->hole_offset, 0, bkpb->hole_length);
    2153           0 :         memcpy(page + (bkpb->hole_offset + bkpb->hole_length),
    2154           0 :                ptr + bkpb->hole_offset,
    2155           0 :                BLCKSZ - (bkpb->hole_offset + bkpb->hole_length));
    2156             :     }
    2157             : 
    2158           0 :     return true;
    2159             : }
    2160             : 
    2161             : #ifndef FRONTEND
    2162             : 
    2163             : /*
    2164             :  * Extract the FullTransactionId from a WAL record.
    2165             :  */
    2166             : FullTransactionId
    2167             : XLogRecGetFullXid(XLogReaderState *record)
    2168             : {
    2169             :     TransactionId xid,
    2170             :                 next_xid;
    2171             :     uint32      epoch;
    2172             : 
    2173             :     /*
    2174             :      * This function is only safe during replay, because it depends on the
    2175             :      * replay state.  See AdvanceNextFullTransactionIdPastXid() for more.
    2176             :      */
    2177             :     Assert(AmStartupProcess() || !IsUnderPostmaster);
    2178             : 
    2179             :     xid = XLogRecGetXid(record);
    2180             :     next_xid = XidFromFullTransactionId(TransamVariables->nextXid);
    2181             :     epoch = EpochFromFullTransactionId(TransamVariables->nextXid);
    2182             : 
    2183             :     /*
    2184             :      * If xid is numerically greater than next_xid, it has to be from the last
    2185             :      * epoch.
    2186             :      */
    2187             :     if (unlikely(xid > next_xid))
    2188             :         --epoch;
    2189             : 
    2190             :     return FullTransactionIdFromEpochAndXid(epoch, xid);
    2191             : }
    2192             : 
    2193             : #endif

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