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Make WAL segment size configurable at initdb time.

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For performance reasons a larger segment size than the default 16MB
can be useful. A larger segment size has two main benefits: Firstly,
in setups using archiving, it makes it easier to write scripts that
can keep up with higher amounts of WAL, secondly, the WAL has to be
written and synced to disk less frequently.

But at the same time large segment size are disadvantageous for
smaller databases. So far the segment size had to be configured at
compile time, often making it unrealistic to choose one fitting to a
particularly load. Therefore change it to a initdb time setting.

This includes a breaking changes to the xlogreader.h API, which now
requires the current segment size to be configured.  For that and
similar reasons a number of binaries had to be taught how to recognize
the current segment size.

Author: Beena Emerson, editorialized by Andres Freund
Reviewed-By: Andres Freund, David Steele, Kuntal Ghosh, Michael
    Paquier, Peter Eisentraut, Robert Hass, Tushar Ahuja
Discussion: https://postgr.es/m/CAOG9ApEAcQ--1ieKbhFzXSQPw_YLmepaa4hNdnY5+ZULpt81Mw@mail.gmail.com
This commit is contained in:
Andres Freund
2017-09-19 22:03:48 -07:00
parent 5ada1fcd0c
commit fc49e24fa6
46 changed files with 898 additions and 501 deletions
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34
src/backend/replication/basebackup.c
View File

@ -357,10 +357,10 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
* shouldn't be such files, but if there are, there's little harm in
* including them.
*/
XLByteToSeg(startptr, startsegno);
XLogFileName(firstoff, ThisTimeLineID, startsegno);
XLByteToPrevSeg(endptr, endsegno);
XLogFileName(lastoff, ThisTimeLineID, endsegno);
XLByteToSeg(startptr, startsegno, wal_segment_size);
XLogFileName(firstoff, ThisTimeLineID, startsegno, wal_segment_size);
XLByteToPrevSeg(endptr, endsegno, wal_segment_size);
XLogFileName(lastoff, ThisTimeLineID, endsegno, wal_segment_size);
dir = AllocateDir("pg_wal");
if (!dir)
@ -415,12 +415,13 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
* Sanity check: the first and last segment should cover startptr and
* endptr, with no gaps in between.
*/
XLogFromFileName(walFiles[0], &tli, &segno);
XLogFromFileName(walFiles[0], &tli, &segno, wal_segment_size);
if (segno != startsegno)
{
char startfname[MAXFNAMELEN];
XLogFileName(startfname, ThisTimeLineID, startsegno);
XLogFileName(startfname, ThisTimeLineID, startsegno,
wal_segment_size);
ereport(ERROR,
(errmsg("could not find WAL file \"%s\"", startfname)));
}
@ -429,12 +430,13 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
XLogSegNo currsegno = segno;
XLogSegNo nextsegno = segno + 1;
XLogFromFileName(walFiles[i], &tli, &segno);
XLogFromFileName(walFiles[i], &tli, &segno, wal_segment_size);
if (!(nextsegno == segno || currsegno == segno))
{
char nextfname[MAXFNAMELEN];
XLogFileName(nextfname, ThisTimeLineID, nextsegno);
XLogFileName(nextfname, ThisTimeLineID, nextsegno,
wal_segment_size);
ereport(ERROR,
(errmsg("could not find WAL file \"%s\"", nextfname)));
}
@ -443,7 +445,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
{
char endfname[MAXFNAMELEN];
XLogFileName(endfname, ThisTimeLineID, endsegno);
XLogFileName(endfname, ThisTimeLineID, endsegno, wal_segment_size);
ereport(ERROR,
(errmsg("could not find WAL file \"%s\"", endfname)));
}
@ -457,7 +459,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
pgoff_t len = 0;
snprintf(pathbuf, MAXPGPATH, XLOGDIR "/%s", walFiles[i]);
XLogFromFileName(walFiles[i], &tli, &segno);
XLogFromFileName(walFiles[i], &tli, &segno, wal_segment_size);
fp = AllocateFile(pathbuf, "rb");
if (fp == NULL)
@ -479,7 +481,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
(errcode_for_file_access(),
errmsg("could not stat file \"%s\": %m",
pathbuf)));
if (statbuf.st_size != XLogSegSize)
if (statbuf.st_size != wal_segment_size)
{
CheckXLogRemoved(segno, tli);
ereport(ERROR,
@ -490,7 +492,9 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
/* send the WAL file itself */
_tarWriteHeader(pathbuf, NULL, &statbuf, false);
while ((cnt = fread(buf, 1, Min(sizeof(buf), XLogSegSize - len), fp)) > 0)
while ((cnt = fread(buf, 1,
Min(sizeof(buf), wal_segment_size - len),
fp)) > 0)
{
CheckXLogRemoved(segno, tli);
/* Send the chunk as a CopyData message */
@ -501,11 +505,11 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
len += cnt;
throttle(cnt);
if (len == XLogSegSize)
if (len == wal_segment_size)
break;
}
if (len != XLogSegSize)
if (len != wal_segment_size)
{
CheckXLogRemoved(segno, tli);
ereport(ERROR,
@ -513,7 +517,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
errmsg("unexpected WAL file size \"%s\"", walFiles[i])));
}
/* XLogSegSize is a multiple of 512, so no need for padding */
/* wal_segment_size is a multiple of 512, so no need for padding */
FreeFile(fp);