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Don't waste the last segment of each 4GB logical log file.

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The comments claimed that wasting the last segment made it easier to do
calculations with XLogRecPtrs, because you don't have problems representing
last-byte-position-plus-1 that way. In my experience, however, it only made
things more complicated, because the there was two ways to represent the
boundary at the beginning of a logical log file: logid = n+1 and xrecoff = 0,
or as xlogid = n and xrecoff = 4GB - XLOG_SEG_SIZE. Some functions were
picky about which representation was used.

Also, use a 64-bit segment number instead of the log/seg combination, to
point to a certain WAL segment. We assume that all platforms have a working
64-bit integer type nowadays.

This is an incompatible change in WAL format, so bumping WAL version number.
This commit is contained in:
Heikki Linnakangas
2012-06-24 18:06:38 +03:00
parent 47c7365e79
commit dfda6ebaec
12 changed files with 413 additions and 554 deletions
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71
src/backend/replication/walsender.c
View File

@@ -87,8 +87,7 @@ int replication_timeout = 60 * 1000; /* maximum time to send one
* but for walsender to read the XLOG.
*/
static int sendFile = -1;
static uint32 sendId = 0;
static uint32 sendSeg = 0;
static XLogSegNo sendSegNo = 0;
static uint32 sendOff = 0;
/*
@@ -977,10 +976,8 @@ XLogRead(char *buf, XLogRecPtr startptr, Size count)
char *p;
XLogRecPtr recptr;
Size nbytes;
uint32 lastRemovedLog;
uint32 lastRemovedSeg;
uint32 log;
uint32 seg;
XLogSegNo lastRemovedSegNo;
XLogSegNo segno;
retry:
p = buf;
@@ -995,7 +992,7 @@ retry:
startoff = recptr.xrecoff % XLogSegSize;
if (sendFile < 0 || !XLByteInSeg(recptr, sendId, sendSeg))
if (sendFile < 0 || !XLByteInSeg(recptr, sendSegNo))
{
char path[MAXPGPATH];
@@ -1003,8 +1000,8 @@ retry:
if (sendFile >= 0)
close(sendFile);
XLByteToSeg(recptr, sendId, sendSeg);
XLogFilePath(path, ThisTimeLineID, sendId, sendSeg);
XLByteToSeg(recptr, sendSegNo);
XLogFilePath(path, ThisTimeLineID, sendSegNo);
sendFile = BasicOpenFile(path, O_RDONLY | PG_BINARY, 0);
if (sendFile < 0)
@@ -1015,20 +1012,15 @@ retry:
* removed or recycled.
*/
if (errno == ENOENT)
{
char filename[MAXFNAMELEN];
XLogFileName(filename, ThisTimeLineID, sendId, sendSeg);
ereport(ERROR,
(errcode_for_file_access(),
errmsg("requested WAL segment %s has already been removed",
filename)));
}
XLogFileNameP(ThisTimeLineID, sendSegNo))));
else
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open file \"%s\" (log file %u, segment %u): %m",
path, sendId, sendSeg)));
errmsg("could not open file \"%s\": %m",
path)));
}
sendOff = 0;
}
@@ -1039,8 +1031,9 @@ retry:
if (lseek(sendFile, (off_t) startoff, SEEK_SET) < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not seek in log file %u, segment %u to offset %u: %m",
sendId, sendSeg, startoff)));
errmsg("could not seek in log segment %s to offset %u: %m",
XLogFileNameP(ThisTimeLineID, sendSegNo),
startoff)));
sendOff = startoff;
}
@@ -1052,11 +1045,13 @@ retry:
readbytes = read(sendFile, p, segbytes);
if (readbytes <= 0)
{
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read from log file %u, segment %u, offset %u, "
"length %lu: %m",
sendId, sendSeg, sendOff, (unsigned long) segbytes)));
errmsg("could not read from log segment %s, offset %u, length %lu: %m",
XLogFileNameP(ThisTimeLineID, sendSegNo),
sendOff, (unsigned long) segbytes)));
}
/* Update state for read */
XLByteAdvance(recptr, readbytes);
@@ -1073,19 +1068,13 @@ retry:
* read() succeeds in that case, but the data we tried to read might
* already have been overwritten with new WAL records.
*/
XLogGetLastRemoved(&lastRemovedLog, &lastRemovedSeg);
XLByteToSeg(startptr, log, seg);
if (log < lastRemovedLog ||
(log == lastRemovedLog && seg <= lastRemovedSeg))
{
char filename[MAXFNAMELEN];
XLogFileName(filename, ThisTimeLineID, log, seg);
XLogGetLastRemoved(&lastRemovedSegNo);
XLByteToSeg(startptr, segno);
if (segno <= lastRemovedSegNo)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("requested WAL segment %s has already been removed",
filename)));
}
XLogFileNameP(ThisTimeLineID, segno))));
/*
* During recovery, the currently-open WAL file might be replaced with the
@@ -1165,24 +1154,13 @@ XLogSend(char *msgbuf, bool *caughtup)
* SendRqstPtr never points to the middle of a WAL record.
*/
startptr = sentPtr;
if (startptr.xrecoff >= XLogFileSize)
{
/*
* crossing a logid boundary, skip the non-existent last log segment
* in previous logical log file.
*/
startptr.xlogid += 1;
startptr.xrecoff = 0;
}
endptr = startptr;
XLByteAdvance(endptr, MAX_SEND_SIZE);
if (endptr.xlogid != startptr.xlogid)
{
/* Don't cross a logfile boundary within one message */
Assert(endptr.xlogid == startptr.xlogid + 1);
endptr.xlogid = startptr.xlogid;
endptr.xrecoff = XLogFileSize;
endptr.xrecoff = 0;
}
/* if we went beyond SendRqstPtr, back off */
@@ -1198,7 +1176,10 @@ XLogSend(char *msgbuf, bool *caughtup)
*caughtup = false;
}
nbytes = endptr.xrecoff - startptr.xrecoff;
if (endptr.xrecoff == 0)
nbytes = 0x100000000L - (uint64) startptr.xrecoff;
else
nbytes = endptr.xrecoff - startptr.xrecoff;
Assert(nbytes <= MAX_SEND_SIZE);
/*