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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/executor | |
| 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/executor')
| -rw-r--r-- | src/backend/executor/execTuples.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/src/backend/executor/execTuples.c b/src/backend/executor/execTuples.c index 00dc3396156..a09aa251e67 100644 --- a/src/backend/executor/execTuples.c +++ b/src/backend/executor/execTuples.c @@ -1044,7 +1044,7 @@ slot_deform_heap_tuple(TupleTableSlot *slot, HeapTuple tuple, uint32 *offp, for (; attnum < natts; attnum++) { - Form_pg_attribute thisatt = TupleDescAttr(tupleDesc, attnum); + CompactAttribute *thisatt = TupleDescCompactAttr(tupleDesc, attnum); if (hasnulls && att_isnull(attnum, bp)) { @@ -2237,7 +2237,7 @@ BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values) */ for (i = 0; i < natts; i++) { - if (!TupleDescAttr(tupdesc, i)->attisdropped) + if (!TupleDescCompactAttr(tupdesc, i)->attisdropped) { /* Non-dropped attributes */ dvalues[i] = InputFunctionCall(&attinmeta->attinfuncs[i], |