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Repair two problems with WAL logging of sequence nextvalI() ops, as

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per recent pghackers discussion: force a new WAL record at first nextval
after a checkpoint, and ensure that xlog is flushed to disk if a nextval
record is the only thing emitted by a transaction.
This commit is contained in:
Tom Lane
2002-03-15 19:20:36 +00:00
parent 0b73fe14f1
commit 01747692fe
6 changed files with 147 additions and 68 deletions
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36
src/backend/commands/sequence.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/commands/sequence.c,v 1.70 2002/03/06 06:09:35 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/commands/sequence.c,v 1.71 2002/03/15 19:20:35 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -286,6 +286,7 @@ nextval(PG_FUNCTION_ARGS)
char *seqname = get_seq_name(seqin);
SeqTable elm;
Buffer buf;
Page page;
Form_pg_sequence seq;
int64 incby,
maxv,
@ -316,6 +317,7 @@ nextval(PG_FUNCTION_ARGS)
seq = read_info("nextval", elm, &buf); /* lock page' buffer and
* read tuple */
page = BufferGetPage(buf);
last = next = result = seq->last_value;
incby = seq->increment_by;
@ -331,11 +333,33 @@ nextval(PG_FUNCTION_ARGS)
log--;
}
/*
* Decide whether we should emit a WAL log record. If so, force up
* the fetch count to grab SEQ_LOG_VALS more values than we actually
* need to cache. (These will then be usable without logging.)
*
* If this is the first nextval after a checkpoint, we must force
* a new WAL record to be written anyway, else replay starting from the
* checkpoint would fail to advance the sequence past the logged
* values. In this case we may as well fetch extra values.
*/
if (log < fetch)
{
fetch = log = fetch - log + SEQ_LOG_VALS;
/* forced log to satisfy local demand for values */
fetch = log = fetch + SEQ_LOG_VALS;
logit = true;
}
else
{
XLogRecPtr redoptr = GetRedoRecPtr();
if (XLByteLE(PageGetLSN(page), redoptr))
{
/* last update of seq was before checkpoint */
fetch = log = fetch + SEQ_LOG_VALS;
logit = true;
}
}
while (fetch) /* try to fetch cache [+ log ] numbers */
{
@ -386,6 +410,9 @@ nextval(PG_FUNCTION_ARGS)
}
}
log -= fetch; /* adjust for any unfetched numbers */
Assert(log >= 0);
/* save info in local cache */
elm->last = result; /* last returned number */
elm->cached = last; /* last fetched number */
@ -396,7 +423,6 @@ nextval(PG_FUNCTION_ARGS)
xl_seq_rec xlrec;
XLogRecPtr recptr;
XLogRecData rdata[2];
Page page = BufferGetPage(buf);
xlrec.node = elm->rel->rd_node;
rdata[0].buffer = InvalidBuffer;
@ -417,15 +443,11 @@ nextval(PG_FUNCTION_ARGS)
PageSetLSN(page, recptr);
PageSetSUI(page, ThisStartUpID);
if (fetch) /* not all numbers were fetched */
log -= fetch;
}
/* update on-disk data */
seq->last_value = last; /* last fetched number */
seq->is_called = true;
Assert(log >= 0);
seq->log_cnt = log; /* how much is logged */
END_CRIT_SECTION();