Line data    Source code

       1              : /*-------------------------------------------------------------------------
       2              :  *
       3              :  * timeline.c
       4              :  *    timeline-related functions.
       5              :  *
       6              :  * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
       7              :  *
       8              :  *-------------------------------------------------------------------------
       9              :  */
      10              : #include "postgres_fe.h"
      11              : 
      12              : #include "access/timeline.h"
      13              : #include "pg_rewind.h"
      14              : 
      15              : /*
      16              :  * This is copy-pasted from the backend readTimeLineHistory, modified to
      17              :  * return a malloc'd array and to work without backend functions.
      18              :  */
      19              : /*
      20              :  * Try to read a timeline's history file.
      21              :  *
      22              :  * If successful, return the list of component TLIs (the given TLI followed by
      23              :  * its ancestor TLIs).  If we can't find the history file, assume that the
      24              :  * timeline has no parents, and return a list of just the specified timeline
      25              :  * ID.
      26              :  */
      27              : TimeLineHistoryEntry *
      28           16 : rewind_parseTimeLineHistory(char *buffer, TimeLineID targetTLI, int *nentries)
      29              : {
      30              :     char       *fline;
      31              :     TimeLineHistoryEntry *entry;
      32           16 :     TimeLineHistoryEntry *entries = NULL;
      33           16 :     int         nlines = 0;
      34           16 :     TimeLineID  lasttli = 0;
      35              :     XLogRecPtr  prevend;
      36              :     char       *bufptr;
      37           16 :     bool        lastline = false;
      38              : 
      39              :     /*
      40              :      * Parse the file...
      41              :      */
      42           16 :     prevend = InvalidXLogRecPtr;
      43           16 :     bufptr = buffer;
      44           50 :     while (!lastline)
      45              :     {
      46              :         char       *ptr;
      47              :         TimeLineID  tli;
      48              :         uint32      switchpoint_hi;
      49              :         uint32      switchpoint_lo;
      50              :         int         nfields;
      51              : 
      52           34 :         fline = bufptr;
      53          731 :         while (*bufptr && *bufptr != '\n')
      54          697 :             bufptr++;
      55           34 :         if (!(*bufptr))
      56           16 :             lastline = true;
      57              :         else
      58           18 :             *bufptr++ = '\0';
      59              : 
      60              :         /* skip leading whitespace and check for # comment */
      61           34 :         for (ptr = fline; *ptr; ptr++)
      62              :         {
      63           17 :             if (!isspace((unsigned char) *ptr))
      64           17 :                 break;
      65              :         }
      66           34 :         if (*ptr == '\0' || *ptr == '#')
      67           17 :             continue;
      68              : 
      69           17 :         nfields = sscanf(fline, "%u\t%X/%08X", &tli, &switchpoint_hi, &switchpoint_lo);
      70              : 
      71           17 :         if (nfields < 1)
      72              :         {
      73              :             /* expect a numeric timeline ID as first field of line */
      74            0 :             pg_log_error("syntax error in history file: %s", fline);
      75            0 :             pg_log_error_detail("Expected a numeric timeline ID.");
      76            0 :             exit(1);
      77              :         }
      78           17 :         if (nfields != 3)
      79              :         {
      80            0 :             pg_log_error("syntax error in history file: %s", fline);
      81            0 :             pg_log_error_detail("Expected a write-ahead log switchpoint location.");
      82            0 :             exit(1);
      83              :         }
      84           17 :         if (entries && tli <= lasttli)
      85              :         {
      86            0 :             pg_log_error("invalid data in history file: %s", fline);
      87            0 :             pg_log_error_detail("Timeline IDs must be in increasing sequence.");
      88            0 :             exit(1);
      89              :         }
      90              : 
      91           17 :         lasttli = tli;
      92              : 
      93           17 :         nlines++;
      94           17 :         entries = pg_realloc(entries, nlines * sizeof(TimeLineHistoryEntry));
      95              : 
      96           17 :         entry = &entries[nlines - 1];
      97           17 :         entry->tli = tli;
      98           17 :         entry->begin = prevend;
      99           17 :         entry->end = ((uint64) (switchpoint_hi)) << 32 | (uint64) switchpoint_lo;
     100           17 :         prevend = entry->end;
     101              : 
     102              :         /* we ignore the remainder of each line */
     103              :     }
     104              : 
     105           16 :     if (entries && targetTLI <= lasttli)
     106              :     {
     107            0 :         pg_log_error("invalid data in history file");
     108            0 :         pg_log_error_detail("Timeline IDs must be less than child timeline's ID.");
     109            0 :         exit(1);
     110              :     }
     111              : 
     112              :     /*
     113              :      * Create one more entry for the "tip" of the timeline, which has no entry
     114              :      * in the history file.
     115              :      */
     116           16 :     nlines++;
     117           16 :     if (entries)
     118           16 :         entries = pg_realloc(entries, nlines * sizeof(TimeLineHistoryEntry));
     119              :     else
     120            0 :         entries = pg_malloc(1 * sizeof(TimeLineHistoryEntry));
     121              : 
     122           16 :     entry = &entries[nlines - 1];
     123           16 :     entry->tli = targetTLI;
     124           16 :     entry->begin = prevend;
     125           16 :     entry->end = InvalidXLogRecPtr;
     126              : 
     127           16 :     *nentries = nlines;
     128           16 :     return entries;
     129              : }