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Allow parallel aggregate on string_agg and array_agg

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This adds combine, serial and deserial functions for the array_agg() and
string_agg() aggregate functions, thus allowing these aggregates to
partake in partial aggregations.  This allows both parallel aggregation to
take place when these aggregates are present and also allows additional
partition-wise aggregation plan shapes to include plans that require
additional aggregation once the partially aggregated results from the
partitions have been combined.

Author: David Rowley
Reviewed-by: Andres Freund, Tomas Vondra, Stephen Frost, Tom Lane
Discussion: https://postgr.es/m/CAKJS1f9sx_6GTcvd6TMuZnNtCh0VhBzhX6FZqw17TgVFH-ga_A@mail.gmail.com
This commit is contained in:
David Rowley
2023-01-23 17:35:01 +13:00
parent 5a3a95385b
commit 16fd03e956
13 changed files with 1103 additions and 30 deletions
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20
src/backend/utils/adt/arrayfuncs.c
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@ -5262,6 +5262,24 @@ array_insert_slice(ArrayType *destArray,
*/
ArrayBuildState *
initArrayResult(Oid element_type, MemoryContext rcontext, bool subcontext)
{
/*
* When using a subcontext, we can afford to start with a somewhat larger
* initial array size. Without subcontexts, we'd better hope that most of
* the states stay small ...
*/
return initArrayResultWithSize(element_type, rcontext, subcontext,
subcontext ? 64 : 8);
}
/*
* initArrayResultWithSize
* As initArrayResult, but allow the initial size of the allocated arrays
* to be specified.
*/
ArrayBuildState *
initArrayResultWithSize(Oid element_type, MemoryContext rcontext,
bool subcontext, int initsize)
{
ArrayBuildState *astate;
MemoryContext arr_context = rcontext;
@ -5276,7 +5294,7 @@ initArrayResult(Oid element_type, MemoryContext rcontext, bool subcontext)
MemoryContextAlloc(arr_context, sizeof(ArrayBuildState));
astate->mcontext = arr_context;
astate->private_cxt = subcontext;
astate->alen = (subcontext ? 64 : 8); /* arbitrary starting array size */
astate->alen = initsize;
astate->dvalues = (Datum *)
MemoryContextAlloc(arr_context, astate->alen * sizeof(Datum));
astate->dnulls = (bool *)