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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/include/access/tupmacs.h | |
| 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/include/access/tupmacs.h')
| -rw-r--r-- | src/include/access/tupmacs.h | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/src/include/access/tupmacs.h b/src/include/access/tupmacs.h index 58b3a58cfd0..622adfa5f86 100644 --- a/src/include/access/tupmacs.h +++ b/src/include/access/tupmacs.h @@ -14,6 +14,7 @@ #ifndef TUPMACS_H #define TUPMACS_H +#include "access/tupdesc.h" #include "catalog/pg_type_d.h" /* for TYPALIGN macros */ @@ -30,8 +31,8 @@ att_isnull(int ATT, const bits8 *BITS) #ifndef FRONTEND /* - * Given a Form_pg_attribute and a pointer into a tuple's data area, - * return the correct value or pointer. + * Given a Form_pg_attribute or CompactAttribute and a pointer into a tuple's + * data area, return the correct value or pointer. * * We return a Datum value in all cases. If the attribute has "byval" false, * we return the same pointer into the tuple data area that we're passed. |