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/*-------------------------------------------------------------------------
*
* multixactfuncs.c
* Functions for accessing multixact-related data.
*
* Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/backend/utils/adt/multixactfuncs.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/multixact.h"
#include "funcapi.h"
#include "utils/builtins.h"
/*
* pg_get_multixact_members
*
* Returns information about the MultiXactMembers of the specified
* MultiXactId.
*/
Datum
pg_get_multixact_members(PG_FUNCTION_ARGS)
{
typedef struct
{
MultiXactMember *members;
int nmembers;
int iter;
} mxact;
MultiXactId mxid = PG_GETARG_TRANSACTIONID(0);
mxact *multi;
FuncCallContext *funccxt;
if (mxid < FirstMultiXactId)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("invalid MultiXactId: %u", mxid)));
if (SRF_IS_FIRSTCALL())
{
MemoryContext oldcxt;
TupleDesc tupdesc;
funccxt = SRF_FIRSTCALL_INIT();
oldcxt = MemoryContextSwitchTo(funccxt->multi_call_memory_ctx);
multi = palloc(sizeof(mxact));
/* no need to allow for old values here */
multi->nmembers = GetMultiXactIdMembers(mxid, &multi->members, false,
false);
multi->iter = 0;
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
funccxt->tuple_desc = tupdesc;
funccxt->attinmeta = TupleDescGetAttInMetadata(tupdesc);
funccxt->user_fctx = multi;
MemoryContextSwitchTo(oldcxt);
}
funccxt = SRF_PERCALL_SETUP();
multi = (mxact *) funccxt->user_fctx;
while (multi->iter < multi->nmembers)
{
HeapTuple tuple;
char *values[2];
values[0] = psprintf("%u", multi->members[multi->iter].xid);
values[1] = mxstatus_to_string(multi->members[multi->iter].status);
tuple = BuildTupleFromCStrings(funccxt->attinmeta, values);
multi->iter++;
pfree(values[0]);
SRF_RETURN_NEXT(funccxt, HeapTupleGetDatum(tuple));
}
SRF_RETURN_DONE(funccxt);
}
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