From bbaf315309ed1194d451326cc8f4f59a45906408 Mon Sep 17 00:00:00 2001 From: Peter Eisentraut Date: Wed, 10 Mar 2021 15:19:37 +0100 Subject: [PATCH] Add bound check before bsearch() for performance In the current lazy vacuum implementation, some index AMs such as btree indexes call lazy_tid_reaped() for each index tuple during ambulkdelete to check if the index tuple points to the (collected) garbage tuple. In that function, we simply call bsearch(), but we should be able to know the result without bsearch() if the index tuple points to the heap tuple that is out of range of the collected garbage tuples. Therefore, add a simple bound check before resorting to bsearch(). Testing has shown that this can give significant performance benefits. Author: Masahiko Sawada Discussion: https://www.postgresql.org/message-id/flat/CA+fd4k76j8jKzJzcx8UqEugvayaMSnQz0iLUt_XgBp-_-bd22A@mail.gmail.com --- src/backend/access/heap/vacuumlazy.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c index d8f847b0e6..4b65205cd1 100644 --- a/src/backend/access/heap/vacuumlazy.c +++ b/src/backend/access/heap/vacuumlazy.c @@ -61,6 +61,7 @@ #include "access/visibilitymap.h" #include "access/xact.h" #include "access/xlog.h" +#include "catalog/index.h" #include "catalog/storage.h" #include "commands/dbcommands.h" #include "commands/progress.h" @@ -2923,8 +2924,24 @@ static bool lazy_tid_reaped(ItemPointer itemptr, void *state) { LVDeadTuples *dead_tuples = (LVDeadTuples *) state; + int64 litem, + ritem, + item; ItemPointer res; + litem = itemptr_encode(&dead_tuples->itemptrs[0]); + ritem = itemptr_encode(&dead_tuples->itemptrs[dead_tuples->num_tuples - 1]); + item = itemptr_encode(itemptr); + + /* + * Doing a simple bound check before bsearch() is useful to avoid the + * extra cost of bsearch(), especially if dead tuples on the heap are + * concentrated in a certain range. Since this function is called for + * every index tuple, it pays to be really fast. + */ + if (item < litem || item > ritem) + return false; + res = (ItemPointer) bsearch((void *) itemptr, (void *) dead_tuples->itemptrs, dead_tuples->num_tuples,