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/utils/cache/relcache.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) (limited to 'src/backend/utils/cache/relcache.c') diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c index d0892cee24d..e230450d2c3 100644 --- a/src/backend/utils/cache/relcache.c +++ b/src/backend/utils/cache/relcache.c @@ -585,6 +585,8 @@ RelationBuildTupleDesc(Relation relation) attp, ATTRIBUTE_FIXED_PART_SIZE); + populate_compact_attribute(relation->rd_att, attnum - 1); + /* Update constraint/default info */ if (attp->attnotnull) constr->has_not_null = true; @@ -674,12 +676,12 @@ RelationBuildTupleDesc(Relation relation) #endif /* - * However, we can easily set the attcacheoff value for the first - * attribute: it must be zero. This eliminates the need for special cases - * for attnum=1 that used to exist in fastgetattr() and index_getattr(). + * We can easily set the attcacheoff value for the first attribute: it + * must be zero. This eliminates the need for special cases for attnum=1 + * that used to exist in fastgetattr() and index_getattr(). */ if (RelationGetNumberOfAttributes(relation) > 0) - TupleDescAttr(relation->rd_att, 0)->attcacheoff = 0; + TupleDescCompactAttr(relation->rd_att, 0)->attcacheoff = 0; /* * Set up constraint/default info @@ -1965,10 +1967,12 @@ formrdesc(const char *relationName, Oid relationReltype, has_not_null |= attrs[i].attnotnull; /* make sure attcacheoff is valid */ TupleDescAttr(relation->rd_att, i)->attcacheoff = -1; + + populate_compact_attribute(relation->rd_att, i); } /* initialize first attribute's attcacheoff, cf RelationBuildTupleDesc */ - TupleDescAttr(relation->rd_att, 0)->attcacheoff = 0; + TupleDescCompactAttr(relation->rd_att, 0)->attcacheoff = 0; /* mark not-null status */ if (has_not_null) @@ -3579,6 +3583,7 @@ RelationBuildLocalRelation(const char *relname, datt->attgenerated = satt->attgenerated; datt->attnotnull = satt->attnotnull; has_not_null |= satt->attnotnull; + populate_compact_attribute(rel->rd_att, i); } if (has_not_null) @@ -4399,10 +4404,12 @@ BuildHardcodedDescriptor(int natts, const FormData_pg_attribute *attrs) memcpy(TupleDescAttr(result, i), &attrs[i], ATTRIBUTE_FIXED_PART_SIZE); /* make sure attcacheoff is valid */ TupleDescAttr(result, i)->attcacheoff = -1; + + populate_compact_attribute(result, i); } /* initialize first attribute's attcacheoff, cf RelationBuildTupleDesc */ - TupleDescAttr(result, 0)->attcacheoff = 0; + TupleDescCompactAttr(result, 0)->attcacheoff = 0; /* Note: we don't bother to set up a TupleConstr entry */ @@ -6166,6 +6173,8 @@ load_relcache_init_file(bool shared) goto read_failed; has_not_null |= attr->attnotnull; + + populate_compact_attribute(rel->rd_att, i); } /* next read the access method specific field */ -- cgit v1.2.3