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/access/common/indextuple.c | 26 +++++++++++++------------- 1 file changed, 13 insertions(+), 13 deletions(-) (limited to 'src/backend/access/common/indextuple.c') diff --git a/src/backend/access/common/indextuple.c b/src/backend/access/common/indextuple.c index bb2c6a2bcc1..37133ed7f80 100644 --- a/src/backend/access/common/indextuple.c +++ b/src/backend/access/common/indextuple.c @@ -303,13 +303,13 @@ nocache_index_getattr(IndexTuple tup, if (!slow) { - Form_pg_attribute att; + CompactAttribute *att; /* * If we get here, there are no nulls up to and including the target * attribute. If we have a cached offset, we can use it. */ - att = TupleDescAttr(tupleDesc, attnum); + att = TupleDescCompactAttr(tupleDesc, attnum); if (att->attcacheoff >= 0) return fetchatt(att, tp + att->attcacheoff); @@ -324,7 +324,7 @@ nocache_index_getattr(IndexTuple tup, for (j = 0; j <= attnum; j++) { - if (TupleDescAttr(tupleDesc, j)->attlen <= 0) + if (TupleDescCompactAttr(tupleDesc, j)->attlen <= 0) { slow = true; break; @@ -347,18 +347,18 @@ nocache_index_getattr(IndexTuple tup, * fixed-width columns, in hope of avoiding future visits to this * routine. */ - TupleDescAttr(tupleDesc, 0)->attcacheoff = 0; + TupleDescCompactAttr(tupleDesc, 0)->attcacheoff = 0; /* we might have set some offsets in the slow path previously */ - while (j < natts && TupleDescAttr(tupleDesc, j)->attcacheoff > 0) + while (j < natts && TupleDescCompactAttr(tupleDesc, j)->attcacheoff > 0) j++; - off = TupleDescAttr(tupleDesc, j - 1)->attcacheoff + - TupleDescAttr(tupleDesc, j - 1)->attlen; + off = TupleDescCompactAttr(tupleDesc, j - 1)->attcacheoff + + TupleDescCompactAttr(tupleDesc, j - 1)->attlen; for (; j < natts; j++) { - Form_pg_attribute att = TupleDescAttr(tupleDesc, j); + CompactAttribute *att = TupleDescCompactAttr(tupleDesc, j); if (att->attlen <= 0) break; @@ -372,7 +372,7 @@ nocache_index_getattr(IndexTuple tup, Assert(j > attnum); - off = TupleDescAttr(tupleDesc, attnum)->attcacheoff; + off = TupleDescCompactAttr(tupleDesc, attnum)->attcacheoff; } else { @@ -392,7 +392,7 @@ nocache_index_getattr(IndexTuple tup, off = 0; for (i = 0;; i++) /* loop exit is at "break" */ { - Form_pg_attribute att = TupleDescAttr(tupleDesc, i); + CompactAttribute *att = TupleDescCompactAttr(tupleDesc, i); if (IndexTupleHasNulls(tup) && att_isnull(i, bp)) { @@ -440,7 +440,7 @@ nocache_index_getattr(IndexTuple tup, } } - return fetchatt(TupleDescAttr(tupleDesc, attnum), tp + off); + return fetchatt(TupleDescCompactAttr(tupleDesc, attnum), tp + off); } /* @@ -490,7 +490,7 @@ index_deform_tuple_internal(TupleDesc tupleDescriptor, for (attnum = 0; attnum < natts; attnum++) { - Form_pg_attribute thisatt = TupleDescAttr(tupleDescriptor, attnum); + CompactAttribute *thisatt = TupleDescCompactAttr(tupleDescriptor, attnum); if (hasnulls && att_isnull(attnum, bp)) { @@ -588,7 +588,7 @@ index_truncate_tuple(TupleDesc sourceDescriptor, IndexTuple source, return CopyIndexTuple(source); /* Create temporary descriptor to scribble on */ - truncdesc = palloc(TupleDescSize(sourceDescriptor)); + truncdesc = CreateTemplateTupleDesc(sourceDescriptor->natts); TupleDescCopy(truncdesc, sourceDescriptor); truncdesc->natts = leavenatts; -- cgit v1.2.3