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neon_walreader: check after local read that the segment still exists.

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Otherwise read might receive zeros/garbage if the file is recycled (renamed) for
as a future segment.
This commit is contained in:
Arseny Sher
2024-05-28 21:28:44 +03:00
committed by Arseny Sher
parent 98dadf8543
commit e6db8069b0
1 changed files with 20 additions and 2 deletions
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22
pgxn/neon/neon_walreader.c
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@@ -184,8 +184,8 @@ NeonWALRead(NeonWALReader *state, char *buf, XLogRecPtr startptr, Size count, Ti
}
else if (state->wre_errno == ENOENT)
{
nwr_log(LOG, "local read failed as segment at %X/%X doesn't exist, attempting remote",
LSN_FORMAT_ARGS(startptr));
nwr_log(LOG, "local read at %X/%X len %zu failed as segment file doesn't exist, attempting remote",
LSN_FORMAT_ARGS(startptr), count);
return NeonWALReadRemote(state, buf, startptr, count, tli);
}
else
@@ -614,6 +614,7 @@ NeonWALReadLocal(NeonWALReader *state, char *buf, XLogRecPtr startptr, Size coun
uint32 startoff;
int segbytes;
int readbytes;
XLogSegNo lastRemovedSegNo;
startoff = XLogSegmentOffset(recptr, state->segcxt.ws_segsize);
@@ -689,6 +690,23 @@ NeonWALReadLocal(NeonWALReader *state, char *buf, XLogRecPtr startptr, Size coun
return false;
}
/*
* Recheck that the segment hasn't been removed while we were reading
* it.
*/
lastRemovedSegNo = XLogGetLastRemovedSegno();
if (state->seg.ws_segno <= lastRemovedSegNo)
{
char fname[MAXFNAMELEN];
state->wre_errno = ENOENT;
XLogFileName(fname, tli, state->seg.ws_segno, state->segcxt.ws_segsize);
snprintf(state->err_msg, sizeof(state->err_msg), "WAL segment %s has been removed during the read, lastRemovedSegNo " UINT64_FORMAT,
fname, lastRemovedSegNo);
return false;
}
/* Update state for read */
recptr += readbytes;
nbytes -= readbytes;