Line data    Source code

       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * timeline.c
       4             :  *    timeline-related functions.
       5             :  *
       6             :  * Portions Copyright (c) 1996-2025, 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          30 : rewind_parseTimeLineHistory(char *buffer, TimeLineID targetTLI, int *nentries)
      29             : {
      30             :     char       *fline;
      31             :     TimeLineHistoryEntry *entry;
      32          30 :     TimeLineHistoryEntry *entries = NULL;
      33          30 :     int         nlines = 0;
      34          30 :     TimeLineID  lasttli = 0;
      35             :     XLogRecPtr  prevend;
      36             :     char       *bufptr;
      37          30 :     bool        lastline = false;
      38             : 
      39             :     /*
      40             :      * Parse the file...
      41             :      */
      42          30 :     prevend = InvalidXLogRecPtr;
      43          30 :     bufptr = buffer;
      44          94 :     while (!lastline)
      45             :     {
      46             :         char       *ptr;
      47             :         TimeLineID  tli;
      48             :         uint32      switchpoint_hi;
      49             :         uint32      switchpoint_lo;
      50             :         int         nfields;
      51             : 
      52          64 :         fline = bufptr;
      53        1344 :         while (*bufptr && *bufptr != '\n')
      54        1280 :             bufptr++;
      55          64 :         if (!(*bufptr))
      56          30 :             lastline = true;
      57             :         else
      58          34 :             *bufptr++ = '\0';
      59             : 
      60             :         /* skip leading whitespace and check for # comment */
      61          64 :         for (ptr = fline; *ptr; ptr++)
      62             :         {
      63          32 :             if (!isspace((unsigned char) *ptr))
      64          32 :                 break;
      65             :         }
      66          64 :         if (*ptr == '\0' || *ptr == '#')
      67          32 :             continue;
      68             : 
      69          32 :         nfields = sscanf(fline, "%u\t%X/%X", &tli, &switchpoint_hi, &switchpoint_lo);
      70             : 
      71          32 :         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          32 :         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          32 :         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          32 :         lasttli = tli;
      92             : 
      93          32 :         nlines++;
      94          32 :         entries = pg_realloc(entries, nlines * sizeof(TimeLineHistoryEntry));
      95             : 
      96          32 :         entry = &entries[nlines - 1];
      97          32 :         entry->tli = tli;
      98          32 :         entry->begin = prevend;
      99          32 :         entry->end = ((uint64) (switchpoint_hi)) << 32 | (uint64) switchpoint_lo;
     100          32 :         prevend = entry->end;
     101             : 
     102             :         /* we ignore the remainder of each line */
     103             :     }
     104             : 
     105          30 :     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          30 :     nlines++;
     117          30 :     if (entries)
     118          30 :         entries = pg_realloc(entries, nlines * sizeof(TimeLineHistoryEntry));
     119             :     else
     120           0 :         entries = pg_malloc(1 * sizeof(TimeLineHistoryEntry));
     121             : 
     122          30 :     entry = &entries[nlines - 1];
     123          30 :     entry->tli = targetTLI;
     124          30 :     entry->begin = prevend;
     125          30 :     entry->end = InvalidXLogRecPtr;
     126             : 
     127          30 :     *nentries = nlines;
     128          30 :     return entries;
     129             : }