Line data    Source code

       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * timeline.c
       4             :  *    timeline-related functions.
       5             :  *
       6             :  * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
       7             :  *
       8             :  *-------------------------------------------------------------------------
       9             :  */
      10             : #include "postgres_fe.h"
      11             : 
      12             : #include "access/timeline.h"
      13             : #include "access/xlog_internal.h"
      14             : #include "pg_rewind.h"
      15             : 
      16             : /*
      17             :  * This is copy-pasted from the backend readTimeLineHistory, modified to
      18             :  * return a malloc'd array and to work without backend functions.
      19             :  */
      20             : /*
      21             :  * Try to read a timeline's history file.
      22             :  *
      23             :  * If successful, return the list of component TLIs (the given TLI followed by
      24             :  * its ancestor TLIs).  If we can't find the history file, assume that the
      25             :  * timeline has no parents, and return a list of just the specified timeline
      26             :  * ID.
      27             :  */
      28             : TimeLineHistoryEntry *
      29          28 : rewind_parseTimeLineHistory(char *buffer, TimeLineID targetTLI, int *nentries)
      30             : {
      31             :     char       *fline;
      32             :     TimeLineHistoryEntry *entry;
      33          28 :     TimeLineHistoryEntry *entries = NULL;
      34          28 :     int         nlines = 0;
      35          28 :     TimeLineID  lasttli = 0;
      36             :     XLogRecPtr  prevend;
      37             :     char       *bufptr;
      38          28 :     bool        lastline = false;
      39             : 
      40             :     /*
      41             :      * Parse the file...
      42             :      */
      43          28 :     prevend = InvalidXLogRecPtr;
      44          28 :     bufptr = buffer;
      45          88 :     while (!lastline)
      46             :     {
      47             :         char       *ptr;
      48             :         TimeLineID  tli;
      49             :         uint32      switchpoint_hi;
      50             :         uint32      switchpoint_lo;
      51             :         int         nfields;
      52             : 
      53          60 :         fline = bufptr;
      54        1260 :         while (*bufptr && *bufptr != '\n')
      55        1200 :             bufptr++;
      56          60 :         if (!(*bufptr))
      57          28 :             lastline = true;
      58             :         else
      59          32 :             *bufptr++ = '\0';
      60             : 
      61             :         /* skip leading whitespace and check for # comment */
      62          60 :         for (ptr = fline; *ptr; ptr++)
      63             :         {
      64          30 :             if (!isspace((unsigned char) *ptr))
      65          30 :                 break;
      66             :         }
      67          60 :         if (*ptr == '\0' || *ptr == '#')
      68          30 :             continue;
      69             : 
      70          30 :         nfields = sscanf(fline, "%u\t%X/%X", &tli, &switchpoint_hi, &switchpoint_lo);
      71             : 
      72          30 :         if (nfields < 1)
      73             :         {
      74             :             /* expect a numeric timeline ID as first field of line */
      75           0 :             pg_log_error("syntax error in history file: %s", fline);
      76           0 :             pg_log_error_detail("Expected a numeric timeline ID.");
      77           0 :             exit(1);
      78             :         }
      79          30 :         if (nfields != 3)
      80             :         {
      81           0 :             pg_log_error("syntax error in history file: %s", fline);
      82           0 :             pg_log_error_detail("Expected a write-ahead log switchpoint location.");
      83           0 :             exit(1);
      84             :         }
      85          30 :         if (entries && tli <= lasttli)
      86             :         {
      87           0 :             pg_log_error("invalid data in history file: %s", fline);
      88           0 :             pg_log_error_detail("Timeline IDs must be in increasing sequence.");
      89           0 :             exit(1);
      90             :         }
      91             : 
      92          30 :         lasttli = tli;
      93             : 
      94          30 :         nlines++;
      95          30 :         entries = pg_realloc(entries, nlines * sizeof(TimeLineHistoryEntry));
      96             : 
      97          30 :         entry = &entries[nlines - 1];
      98          30 :         entry->tli = tli;
      99          30 :         entry->begin = prevend;
     100          30 :         entry->end = ((uint64) (switchpoint_hi)) << 32 | (uint64) switchpoint_lo;
     101          30 :         prevend = entry->end;
     102             : 
     103             :         /* we ignore the remainder of each line */
     104             :     }
     105             : 
     106          28 :     if (entries && targetTLI <= lasttli)
     107             :     {
     108           0 :         pg_log_error("invalid data in history file");
     109           0 :         pg_log_error_detail("Timeline IDs must be less than child timeline's ID.");
     110           0 :         exit(1);
     111             :     }
     112             : 
     113             :     /*
     114             :      * Create one more entry for the "tip" of the timeline, which has no entry
     115             :      * in the history file.
     116             :      */
     117          28 :     nlines++;
     118          28 :     if (entries)
     119          28 :         entries = pg_realloc(entries, nlines * sizeof(TimeLineHistoryEntry));
     120             :     else
     121           0 :         entries = pg_malloc(1 * sizeof(TimeLineHistoryEntry));
     122             : 
     123          28 :     entry = &entries[nlines - 1];
     124          28 :     entry->tli = targetTLI;
     125          28 :     entry->begin = prevend;
     126          28 :     entry->end = InvalidXLogRecPtr;
     127             : 
     128          28 :     *nentries = nlines;
     129          28 :     return entries;
     130             : }