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Optimize various aggregate deserialization functions

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The serialized representation of an internal aggregate state is a bytea
value.  In each deserial function, in order to "receive" the bytea value
we appended it onto a short-lived StringInfoData using
appendBinaryStringInfo.  This was a little wasteful as it meant having to
palloc memory, copy a (possibly long) series of bytes then later pfree
that memory.  Instead of going to this extra trouble, we can just fake up
a StringInfoData and point the data directly at the bytea's payload.  This
should help increase the performance of internal aggregate
deserialization.

Reviewed-by: Michael Paquier
Discussion: https://postgr.es/m/CAApHDvr=e-YOigriSHHm324a40HPqcUhSp6pWWgjz5WwegR=cQ@mail.gmail.com
This commit is contained in:
David Rowley
2023-10-09 17:25:16 +13:00
parent 7cc2f59dd5
commit 608fd198de
3 changed files with 42 additions and 42 deletions
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12
src/backend/utils/adt/varlena.c
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@@ -5289,12 +5289,13 @@ string_agg_deserialize(PG_FUNCTION_ARGS)
sstate = PG_GETARG_BYTEA_PP(0);
/*
* Copy the bytea into a StringInfo so that we can "receive" it using the
* standard recv-function infrastructure.
* Fake up a StringInfo pointing to the bytea's value so we can "receive"
* the serialized aggregate state value.
*/
initStringInfo(&buf);
appendBinaryStringInfo(&buf,
VARDATA_ANY(sstate), VARSIZE_ANY_EXHDR(sstate));
buf.data = VARDATA_ANY(sstate);
buf.len = VARSIZE_ANY_EXHDR(sstate);
buf.maxlen = 0;
buf.cursor = 0;
result = makeStringAggState(fcinfo);
@@ -5307,7 +5308,6 @@ string_agg_deserialize(PG_FUNCTION_ARGS)
appendBinaryStringInfo(result, data, datalen);
pq_getmsgend(&buf);
pfree(buf.data);
PG_RETURN_POINTER(result);
}