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| author | David Rowley <drowley@postgresql.org> | 2024-12-03 16:50:59 +1300 |
|---|---|---|
| committer | David Rowley <drowley@postgresql.org> | 2024-12-03 16:50:59 +1300 |
| commit | d28dff3f6cd6a7562fb2c211ac0fb74a33ffd032 (patch) | |
| tree | 4b7126eba2dcbed5e08714b4ab2d8577058814c3 /src/backend/commands/tablecmds.c | |
| parent | e4c8865196f6ad6bb3473bcad1d2ad51147e4513 (diff) | |
| download | postgresql-d28dff3f6cd6a7562fb2c211ac0fb74a33ffd032.tar.gz postgresql-d28dff3f6cd6a7562fb2c211ac0fb74a33ffd032.zip | |
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
Diffstat (limited to 'src/backend/commands/tablecmds.c')
| -rw-r--r-- | src/backend/commands/tablecmds.c | 4 |
1 files changed, 4 insertions, 0 deletions
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; |