From 022350b8495a8a7ff0ff8dd6791572e91e7cd6fe Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Sat, 1 Aug 2020 11:49:13 +0900 Subject: [PATCH] Minimize slot creation for multi-inserts of pg_shdepend When doing multiple insertions in pg_shdepend for the copy of dependencies from a template database in CREATE DATABASE, the same number of slots would have been created and used all the time. As the number of items to insert is not known in advance, this makes most of the slots created for nothing. This improves the slot handling so as slot creation only happens when needed, minimizing the overhead of the operation. Author: Michael Paquier Reviewed-by: Daniel Gustafsson Discussion: https://postgr.es/m/20200731024148.GB3317@paquier.xyz --- src/backend/catalog/pg_shdepend.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/src/backend/catalog/pg_shdepend.c b/src/backend/catalog/pg_shdepend.c index ef2b87927c..30b234e90e 100644 --- a/src/backend/catalog/pg_shdepend.c +++ b/src/backend/catalog/pg_shdepend.c @@ -809,15 +809,19 @@ copyTemplateDependencies(Oid templateDbId, Oid newDbId) int slotCount; CatalogIndexState indstate; TupleTableSlot **slot; - int nslots; + int nslots, + max_slots; + bool slot_init = true; sdepRel = table_open(SharedDependRelationId, RowExclusiveLock); sdepDesc = RelationGetDescr(sdepRel); - nslots = MAX_PGSHDEPEND_INSERT_BYTES / sizeof(FormData_pg_shdepend); - slot = palloc(sizeof(TupleTableSlot *) * nslots); - for (int i = 0; i < nslots; i++) - slot[i] = MakeSingleTupleTableSlot(sdepDesc, &TTSOpsHeapTuple); + /* + * Allocate the slots to use, but delay initialization until we know that + * they will be used. + */ + max_slots = MAX_PGSHDEPEND_INSERT_BYTES / sizeof(FormData_pg_shdepend); + slot = palloc(sizeof(TupleTableSlot *) * max_slots); indstate = CatalogOpenIndexes(sdepRel); @@ -842,6 +846,9 @@ copyTemplateDependencies(Oid templateDbId, Oid newDbId) { Form_pg_shdepend shdep; + if (slot_init) + slot[slotCount] = MakeSingleTupleTableSlot(sdepDesc, &TTSOpsHeapTuple); + ExecClearTuple(slot[slotCount]); shdep = (Form_pg_shdepend) GETSTRUCT(tup); @@ -858,10 +865,11 @@ copyTemplateDependencies(Oid templateDbId, Oid newDbId) slotCount++; /* If slots are full, insert a batch of tuples */ - if (slotCount == nslots) + if (slotCount == max_slots) { CatalogTuplesMultiInsertWithInfo(sdepRel, slot, slotCount, indstate); slotCount = 0; + slot_init = false; } } @@ -874,6 +882,8 @@ copyTemplateDependencies(Oid templateDbId, Oid newDbId) CatalogCloseIndexes(indstate); table_close(sdepRel, RowExclusiveLock); + /* Drop only the number of slots used */ + nslots = slot_init ? slotCount : max_slots; for (int i = 0; i < nslots; i++) ExecDropSingleTupleTableSlot(slot[i]); pfree(slot);