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+4...@mail.gmail.com Reviewed-by: Andres Freund, Victor Yegorov Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/d28dff3f6cd6a7562fb2c211ac0fb74a33ffd032 Modified Files -------------- src/backend/access/common/heaptuple.c | 53 ++++++++++--------- src/backend/access/common/indextuple.c | 26 ++++----- src/backend/access/common/tupdesc.c | 70 ++++++++++++++++++++---- src/backend/access/spgist/spgutils.c | 4 +- src/backend/catalog/index.c | 2 + src/backend/commands/tablecmds.c | 4 ++ src/backend/executor/execTuples.c | 4 +- src/backend/utils/cache/relcache.c | 21 +++++--- src/backend/utils/cache/typcache.c | 13 +++++ src/include/access/htup_details.h | 4 +- src/include/access/itup.h | 10 ++-- src/include/access/tupdesc.h | 97 ++++++++++++++++++++++++++++++++-- src/include/access/tupmacs.h | 5 +- src/tools/pgindent/typedefs.list | 1 + 14 files changed, 246 insertions(+), 68 deletions(-)
