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In UpdateStats(), don't bother to update the pg_class row if it already

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contains the correct statistics.  This is a partial solution for the
problem of allowing concurrent CREATE INDEX commands: unless they commit
at nearly the same instant, the second one will see the first one's
pg_class updates as committed, and won't try to update again, thus
avoiding the 'tuple concurrently updated' failure.
This commit is contained in:
Tom Lane 2002-09-22 23:03:58 +00:00
parent 1d01d484c1
commit df3e7b3a51
1 changed files with 40 additions and 54 deletions
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94
src/backend/catalog/index.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/catalog/index.c,v 1.198 2002/09/22 19:42:50 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/catalog/index.c,v 1.199 2002/09/22 23:03:58 tgl Exp $
*
*
* INTERFACE ROUTINES
@ -1168,13 +1168,8 @@ setRelhasindex(Oid relid, bool hasindex, bool isprimary, Oid reltoastidxid)
}
if (!HeapTupleIsValid(tuple))
{
if (pg_class_scan)
heap_endscan(pg_class_scan);
heap_close(pg_class, RowExclusiveLock);
elog(ERROR, "setRelhasindex: cannot find relation %u in pg_class",
relid);
}
/*
* Update fields in the pg_class tuple.
@ -1319,11 +1314,7 @@ UpdateStats(Oid relid, double reltuples)
HeapTuple tuple;
HeapTuple newtup;
BlockNumber relpages;
int i;
Form_pg_class rd_rel;
Datum values[Natts_pg_class];
char nulls[Natts_pg_class];
char replace[Natts_pg_class];
HeapScanDesc pg_class_scan = NULL;
bool in_place_upd;
@ -1375,13 +1366,8 @@ UpdateStats(Oid relid, double reltuples)
}
if (!HeapTupleIsValid(tuple))
{
if (pg_class_scan)
heap_endscan(pg_class_scan);
heap_close(pg_class, RowExclusiveLock);
elog(ERROR, "UpdateStats: cannot find relation %u in pg_class",
relid);
}
/*
* Figure values to insert.
@ -1417,50 +1403,41 @@ UpdateStats(Oid relid, double reltuples)
}
/*
* We shouldn't have to do this, but we do... Modify the reldesc in
* place with the new values so that the cache contains the latest
* copy.
* Update statistics in pg_class, if they changed. (Avoiding an
* unnecessary update is not just a tiny performance improvement;
* it also reduces the window wherein concurrent CREATE INDEX commands
* may conflict.)
*/
whichRel->rd_rel->relpages = (int32) relpages;
whichRel->rd_rel->reltuples = reltuples;
rd_rel = (Form_pg_class) GETSTRUCT(tuple);
/*
* Update statistics in pg_class.
*/
if (in_place_upd)
if (rd_rel->relpages != (int32) relpages ||
rd_rel->reltuples != (float4) reltuples)
{
/*
* At bootstrap time, we don't need to worry about concurrency or
* visibility of changes, so we cheat. Also cheat if REINDEX.
*/
rd_rel = (Form_pg_class) GETSTRUCT(tuple);
LockBuffer(pg_class_scan->rs_cbuf, BUFFER_LOCK_EXCLUSIVE);
rd_rel->relpages = (int32) relpages;
rd_rel->reltuples = reltuples;
LockBuffer(pg_class_scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
WriteNoReleaseBuffer(pg_class_scan->rs_cbuf);
if (!IsBootstrapProcessingMode())
CacheInvalidateHeapTuple(pg_class, tuple);
}
else
{
/* During normal processing, must work harder. */
for (i = 0; i < Natts_pg_class; i++)
if (in_place_upd)
{
nulls[i] = ' ';
replace[i] = ' ';
values[i] = (Datum) NULL;
/*
* At bootstrap time, we don't need to worry about concurrency or
* visibility of changes, so we cheat. Also cheat if REINDEX.
*/
LockBuffer(pg_class_scan->rs_cbuf, BUFFER_LOCK_EXCLUSIVE);
rd_rel->relpages = (int32) relpages;
rd_rel->reltuples = (float4) reltuples;
LockBuffer(pg_class_scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
WriteNoReleaseBuffer(pg_class_scan->rs_cbuf);
if (!IsBootstrapProcessingMode())
CacheInvalidateHeapTuple(pg_class, tuple);
}
else
{
/* During normal processing, must work harder. */
newtup = heap_copytuple(tuple);
rd_rel = (Form_pg_class) GETSTRUCT(newtup);
rd_rel->relpages = (int32) relpages;
rd_rel->reltuples = (float4) reltuples;
simple_heap_update(pg_class, &tuple->t_self, newtup);
CatalogUpdateIndexes(pg_class, newtup);
heap_freetuple(newtup);
}
replace[Anum_pg_class_relpages - 1] = 'r';
values[Anum_pg_class_relpages - 1] = Int32GetDatum((int32) relpages);
replace[Anum_pg_class_reltuples - 1] = 'r';
values[Anum_pg_class_reltuples - 1] = Float4GetDatum((float4) reltuples);
newtup = heap_modifytuple(tuple, pg_class, values, nulls, replace);
simple_heap_update(pg_class, &tuple->t_self, newtup);
CatalogUpdateIndexes(pg_class, newtup);
heap_freetuple(newtup);
}
if (!pg_class_scan)
@ -1468,6 +1445,15 @@ UpdateStats(Oid relid, double reltuples)
else
heap_endscan(pg_class_scan);
/*
* We shouldn't have to do this, but we do... Modify the reldesc in
* place with the new values so that the cache contains the latest
* copy. (XXX is this really still necessary? The relcache will get
* fixed at next CommandCounterIncrement, so why bother here?)
*/
whichRel->rd_rel->relpages = (int32) relpages;
whichRel->rd_rel->reltuples = (float4) reltuples;
heap_close(pg_class, RowExclusiveLock);
relation_close(whichRel, NoLock);
}