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/access/spgist/spgutils.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'src/backend/access/spgist/spgutils.c') diff --git a/src/backend/access/spgist/spgutils.c b/src/backend/access/spgist/spgutils.c index e93d9869b27..da858182173 100644 --- a/src/backend/access/spgist/spgutils.c +++ b/src/backend/access/spgist/spgutils.c @@ -331,7 +331,9 @@ getSpGistTupleDesc(Relation index, SpGistTypeDesc *keyType) att->attcollation = InvalidOid; /* In case we changed typlen, we'd better reset following offsets */ for (int i = spgFirstIncludeColumn; i < outTupDesc->natts; i++) - TupleDescAttr(outTupDesc, i)->attcacheoff = -1; + TupleDescCompactAttr(outTupDesc, i)->attcacheoff = -1; + + populate_compact_attribute(outTupDesc, spgKeyColumn); } return outTupDesc; } -- cgit v1.2.3