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Avoid useless palloc during transaction commit

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We can allocate the initial relations-to-drop array when first needed,
instead of at function entry; this avoids allocating it when the
function is not going to do anything, which is most of the time.

Backpatch to 9.3, where this behavior was introduced by commit
279628a0a7.

There's more that could be done here, such as possible reworking of the
code to avoid having to palloc anything, but that doesn't sound as
backpatchable as this relatively minor change.

Per complaint from Noah Misch in
20131031145234.GA621493@tornado.leadboat.com
This commit is contained in:
Alvaro Herrera 2013-12-20 12:37:30 -03:00
parent c32afe53c2
commit 6130208e75
1 changed files with 11 additions and 7 deletions
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18
src/backend/catalog/storage.c
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@ -314,8 +314,8 @@ smgrDoPendingDeletes(bool isCommit)
PendingRelDelete *next;
int nrels = 0,
i = 0,
maxrels = 8;
SMgrRelation *srels = palloc(maxrels * sizeof(SMgrRelation));
maxrels = 0;
SMgrRelation *srels = NULL;
prev = NULL;
for (pending = pendingDeletes; pending != NULL; pending = next)
@ -340,8 +340,13 @@ smgrDoPendingDeletes(bool isCommit)
srel = smgropen(pending->relnode, pending->backend);
/* extend the array if needed (double the size) */
if (maxrels <= nrels)
/* allocate the initial array, or extend it, if needed */
if (maxrels == 0)
{
maxrels = 8;
srels = palloc(sizeof(SMgrRelation) * maxrels );
}
else if (maxrels <= nrels)
{
maxrels *= 2;
srels = repalloc(srels, sizeof(SMgrRelation) * maxrels);
@ -361,10 +366,9 @@ smgrDoPendingDeletes(bool isCommit)
for (i = 0; i < nrels; i++)
smgrclose(srels[i]);
pfree(srels);
}
pfree(srels);
}
/*