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/*-------------------------------------------------------------------------
*
* timeline.c
* timeline-related functions.
*
* Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
*
*-------------------------------------------------------------------------
*/
#include "postgres_fe.h"
#include "access/timeline.h"
#include "pg_rewind.h"
/*
* This is copy-pasted from the backend readTimeLineHistory, modified to
* return a malloc'd array and to work without backend functions.
*/
/*
* Try to read a timeline's history file.
*
* If successful, return the list of component TLIs (the given TLI followed by
* its ancestor TLIs). If we can't find the history file, assume that the
* timeline has no parents, and return a list of just the specified timeline
* ID.
*/
TimeLineHistoryEntry *
rewind_parseTimeLineHistory(char *buffer, TimeLineID targetTLI, int *nentries)
{
char *fline;
TimeLineHistoryEntry *entry;
TimeLineHistoryEntry *entries = NULL;
int nlines = 0;
TimeLineID lasttli = 0;
XLogRecPtr prevend;
char *bufptr;
bool lastline = false;
/*
* Parse the file...
*/
prevend = InvalidXLogRecPtr;
bufptr = buffer;
while (!lastline)
{
char *ptr;
TimeLineID tli;
uint32 switchpoint_hi;
uint32 switchpoint_lo;
int nfields;
fline = bufptr;
while (*bufptr && *bufptr != '\n')
bufptr++;
if (!(*bufptr))
lastline = true;
else
*bufptr++ = '\0';
/* skip leading whitespace and check for # comment */
for (ptr = fline; *ptr; ptr++)
{
if (!isspace((unsigned char) *ptr))
break;
}
if (*ptr == '\0' || *ptr == '#')
continue;
nfields = sscanf(fline, "%u\t%X/%X", &tli, &switchpoint_hi, &switchpoint_lo);
if (nfields < 1)
{
/* expect a numeric timeline ID as first field of line */
pg_log_error("syntax error in history file: %s", fline);
pg_log_error_detail("Expected a numeric timeline ID.");
exit(1);
}
if (nfields != 3)
{
pg_log_error("syntax error in history file: %s", fline);
pg_log_error_detail("Expected a write-ahead log switchpoint location.");
exit(1);
}
if (entries && tli <= lasttli)
{
pg_log_error("invalid data in history file: %s", fline);
pg_log_error_detail("Timeline IDs must be in increasing sequence.");
exit(1);
}
lasttli = tli;
nlines++;
entries = pg_realloc(entries, nlines * sizeof(TimeLineHistoryEntry));
entry = &entries[nlines - 1];
entry->tli = tli;
entry->begin = prevend;
entry->end = ((uint64) (switchpoint_hi)) << 32 | (uint64) switchpoint_lo;
prevend = entry->end;
/* we ignore the remainder of each line */
}
if (entries && targetTLI <= lasttli)
{
pg_log_error("invalid data in history file");
pg_log_error_detail("Timeline IDs must be less than child timeline's ID.");
exit(1);
}
/*
* Create one more entry for the "tip" of the timeline, which has no entry
* in the history file.
*/
nlines++;
if (entries)
entries = pg_realloc(entries, nlines * sizeof(TimeLineHistoryEntry));
else
entries = pg_malloc(1 * sizeof(TimeLineHistoryEntry));
entry = &entries[nlines - 1];
entry->tli = targetTLI;
entry->begin = prevend;
entry->end = InvalidXLogRecPtr;
*nentries = nlines;
return entries;
}
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