Line data    Source code

       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * multixactfuncs.c
       4             :  *    Functions for accessing multixact-related data.
       5             :  *
       6             :  * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
       7             :  * Portions Copyright (c) 1994, Regents of the University of California
       8             :  *
       9             :  * IDENTIFICATION
      10             :  *    src/backend/utils/adt/multixactfuncs.c
      11             :  *
      12             :  *-------------------------------------------------------------------------
      13             :  */
      14             : 
      15             : #include "postgres.h"
      16             : 
      17             : #include "access/multixact.h"
      18             : #include "funcapi.h"
      19             : #include "utils/builtins.h"
      20             : 
      21             : /*
      22             :  * pg_get_multixact_members
      23             :  *
      24             :  * Returns information about the MultiXactMembers of the specified
      25             :  * MultiXactId.
      26             :  */
      27             : Datum
      28      396156 : pg_get_multixact_members(PG_FUNCTION_ARGS)
      29             : {
      30             :     typedef struct
      31             :     {
      32             :         MultiXactMember *members;
      33             :         int         nmembers;
      34             :         int         iter;
      35             :     } mxact;
      36      396156 :     MultiXactId mxid = PG_GETARG_TRANSACTIONID(0);
      37             :     mxact      *multi;
      38             :     FuncCallContext *funccxt;
      39             : 
      40      396156 :     if (mxid < FirstMultiXactId)
      41           0 :         ereport(ERROR,
      42             :                 (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
      43             :                  errmsg("invalid MultiXactId: %u", mxid)));
      44             : 
      45      396156 :     if (SRF_IS_FIRSTCALL())
      46             :     {
      47             :         MemoryContext oldcxt;
      48             :         TupleDesc   tupdesc;
      49             : 
      50       19980 :         funccxt = SRF_FIRSTCALL_INIT();
      51       19980 :         oldcxt = MemoryContextSwitchTo(funccxt->multi_call_memory_ctx);
      52             : 
      53       19980 :         multi = palloc_object(mxact);
      54             :         /* no need to allow for old values here */
      55       19980 :         multi->nmembers = GetMultiXactIdMembers(mxid, &multi->members, false,
      56             :                                                 false);
      57       19980 :         multi->iter = 0;
      58             : 
      59       19980 :         if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
      60           0 :             elog(ERROR, "return type must be a row type");
      61       19980 :         funccxt->tuple_desc = tupdesc;
      62       19980 :         funccxt->attinmeta = TupleDescGetAttInMetadata(tupdesc);
      63       19980 :         funccxt->user_fctx = multi;
      64             : 
      65       19980 :         MemoryContextSwitchTo(oldcxt);
      66             :     }
      67             : 
      68      396156 :     funccxt = SRF_PERCALL_SETUP();
      69      396156 :     multi = (mxact *) funccxt->user_fctx;
      70             : 
      71      396156 :     while (multi->iter < multi->nmembers)
      72             :     {
      73             :         HeapTuple   tuple;
      74             :         char       *values[2];
      75             : 
      76      376176 :         values[0] = psprintf("%u", multi->members[multi->iter].xid);
      77      376176 :         values[1] = mxstatus_to_string(multi->members[multi->iter].status);
      78             : 
      79      376176 :         tuple = BuildTupleFromCStrings(funccxt->attinmeta, values);
      80             : 
      81      376176 :         multi->iter++;
      82      376176 :         pfree(values[0]);
      83      376176 :         SRF_RETURN_NEXT(funccxt, HeapTupleGetDatum(tuple));
      84             :     }
      85             : 
      86       19980 :     SRF_RETURN_DONE(funccxt);
      87             : }