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Switch some system functions to use get_call_result_type()

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This shaves some code by replacing the combinations of
CreateTemplateTupleDesc()/TupleDescInitEntry() hardcoding a mapping of
the attributes listed in pg_proc.dat by get_call_result_type() to build
the TupleDesc needed for the rows generated.

get_call_result_type() is more expensive than the former style, but this
removes some duplication with the lists of OUT parameters (pg_proc.dat
and the attributes hardcoded in these code paths).  This is applied to
functions that are not considered as critical (aka that could be called
repeatedly for monitoring purposes).

Author: Bharath Rupireddy
Reviewed-by: Robert Haas, Álvaro Herrera, Tom Lane, Michael Paquier
Discussion: https://postgr.es/m/CALj2ACV23HW5HP5hFjd89FNS-z5X8r2jNXdMXcpN2BgTtKd87w@mail.gmail.com
This commit is contained in:
Michael Paquier
2022-12-21 10:11:22 +09:00
parent f03bd5717e
commit 22e3b55805
12 changed files with 61 additions and 285 deletions
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26
contrib/old_snapshot/time_mapping.c
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@ -38,7 +38,6 @@ PG_MODULE_MAGIC;
PG_FUNCTION_INFO_V1(pg_old_snapshot_time_mapping);
static OldSnapshotTimeMapping *GetOldSnapshotTimeMapping(void);
static TupleDesc MakeOldSnapshotTimeMappingTupleDesc(void);
static HeapTuple MakeOldSnapshotTimeMappingTuple(TupleDesc tupdesc,
OldSnapshotTimeMapping *mapping);
@ -54,12 +53,15 @@ pg_old_snapshot_time_mapping(PG_FUNCTION_ARGS)
if (SRF_IS_FIRSTCALL())
{
MemoryContext oldcontext;
TupleDesc tupdesc;
funcctx = SRF_FIRSTCALL_INIT();
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
mapping = GetOldSnapshotTimeMapping();
funcctx->user_fctx = mapping;
funcctx->tuple_desc = MakeOldSnapshotTimeMappingTupleDesc();
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
funcctx->tuple_desc = tupdesc;
MemoryContextSwitchTo(oldcontext);
}
@ -101,26 +103,6 @@ GetOldSnapshotTimeMapping(void)
return mapping;
}
/*
* Build a tuple descriptor for the pg_old_snapshot_time_mapping() SRF.
*/
static TupleDesc
MakeOldSnapshotTimeMappingTupleDesc(void)
{
TupleDesc tupdesc;
tupdesc = CreateTemplateTupleDesc(NUM_TIME_MAPPING_COLUMNS);
TupleDescInitEntry(tupdesc, (AttrNumber) 1, "array_offset",
INT4OID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 2, "end_timestamp",
TIMESTAMPTZOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 3, "newest_xmin",
XIDOID, -1, 0);
return BlessTupleDesc(tupdesc);
}
/*
* Convert one entry from the old snapshot time mapping to a HeapTuple.
*/