From d28dff3f6cd6a7562fb2c211ac0fb74a33ffd032 Mon Sep 17 00:00:00 2001 From: David Rowley Date: Tue, 3 Dec 2024 16:50:59 +1300 Subject: Introduce CompactAttribute array in TupleDesc The new compact_attrs array stores a few select fields from FormData_pg_attribute in a more compact way, using only 16 bytes per column instead of the 104 bytes that FormData_pg_attribute uses. Using CompactAttribute allows performance-critical operations such as tuple deformation to be performed without looking at the FormData_pg_attribute element in TupleDesc which means fewer cacheline accesses. With this change, NAMEDATALEN could be increased with a much smaller negative impact on performance. For some workloads, tuple deformation can be the most CPU intensive part of processing the query. Some testing with 16 columns on a table where the first column is variable length showed around a 10% increase in transactions per second for an OLAP type query performing aggregation on the 16th column. However, in certain cases, the increases were much higher, up to ~25% on one AMD Zen4 machine. This also makes pg_attribute.attcacheoff redundant. A follow-on commit will remove it, thus shrinking the FormData_pg_attribute struct by 4 bytes. Author: David Rowley Discussion: https://postgr.es/m/CAApHDvrBztXP3yx=NKNmo3xwFAFhEdyPnvrDg3=M0RhDs+4vYw@mail.gmail.com Reviewed-by: Andres Freund, Victor Yegorov --- src/backend/commands/tablecmds.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'src/backend/commands/tablecmds.c') diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c index 6ccae4cb4a8..49374782625 100644 --- a/src/backend/commands/tablecmds.c +++ b/src/backend/commands/tablecmds.c @@ -980,6 +980,8 @@ DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId, cookedDefaults = lappend(cookedDefaults, cooked); attr->atthasdef = true; } + + populate_compact_attribute(descriptor, attnum - 1); } /* @@ -1396,6 +1398,8 @@ BuildDescForRelation(const List *columns) att->attstorage = entry->storage; else if (entry->storage_name) att->attstorage = GetAttributeStorage(att->atttypid, entry->storage_name); + + populate_compact_attribute(desc, attnum - 1); } return desc; -- cgit v1.2.3