From 6130208e75c98d76b526ac2ac08cedbd17b9f00d Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Fri, 20 Dec 2013 12:37:30 -0300
Subject: [PATCH] Avoid useless palloc during transaction commit
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
279628a0a7cf5.
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
---
src/backend/catalog/storage.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
diff --git a/src/backend/catalog/storage.c b/src/backend/catalog/storage.c
index 971a149d590..892f1636a90 100644
--- a/src/backend/catalog/storage.c
+++ b/src/backend/catalog/storage.c
@@ -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);
+ }
}
/*
--
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