Line data    Source code

       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * multixactfuncs.c
       4             :  *    Functions for accessing multixact-related data.
       5             :  *
       6             :  * Portions Copyright (c) 1996-2026, 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/htup_details.h"
      18             : #include "access/multixact.h"
      19             : #include "access/multixact_internal.h"
      20             : #include "catalog/pg_authid_d.h"
      21             : #include "funcapi.h"
      22             : #include "miscadmin.h"
      23             : #include "utils/acl.h"
      24             : #include "utils/builtins.h"
      25             : 
      26             : /*
      27             :  * pg_get_multixact_members
      28             :  *
      29             :  * Returns information about the MultiXactMembers of the specified
      30             :  * MultiXactId.
      31             :  */
      32             : Datum
      33      396156 : pg_get_multixact_members(PG_FUNCTION_ARGS)
      34             : {
      35             :     typedef struct
      36             :     {
      37             :         MultiXactMember *members;
      38             :         int         nmembers;
      39             :         int         iter;
      40             :     } mxact;
      41      396156 :     MultiXactId mxid = PG_GETARG_TRANSACTIONID(0);
      42             :     mxact      *multi;
      43             :     FuncCallContext *funccxt;
      44             : 
      45      396156 :     if (mxid < FirstMultiXactId)
      46           0 :         ereport(ERROR,
      47             :                 (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
      48             :                  errmsg("invalid MultiXactId: %u", mxid)));
      49             : 
      50      396156 :     if (SRF_IS_FIRSTCALL())
      51             :     {
      52             :         MemoryContext oldcxt;
      53             :         TupleDesc   tupdesc;
      54             : 
      55       19980 :         funccxt = SRF_FIRSTCALL_INIT();
      56       19980 :         oldcxt = MemoryContextSwitchTo(funccxt->multi_call_memory_ctx);
      57             : 
      58       19980 :         multi = palloc_object(mxact);
      59             :         /* no need to allow for old values here */
      60       19980 :         multi->nmembers = GetMultiXactIdMembers(mxid, &multi->members, false,
      61             :                                                 false);
      62       19980 :         multi->iter = 0;
      63             : 
      64       19980 :         if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
      65           0 :             elog(ERROR, "return type must be a row type");
      66       19980 :         funccxt->tuple_desc = tupdesc;
      67       19980 :         funccxt->attinmeta = TupleDescGetAttInMetadata(tupdesc);
      68       19980 :         funccxt->user_fctx = multi;
      69             : 
      70       19980 :         MemoryContextSwitchTo(oldcxt);
      71             :     }
      72             : 
      73      396156 :     funccxt = SRF_PERCALL_SETUP();
      74      396156 :     multi = (mxact *) funccxt->user_fctx;
      75             : 
      76      396156 :     while (multi->iter < multi->nmembers)
      77             :     {
      78             :         HeapTuple   tuple;
      79             :         char       *values[2];
      80             : 
      81      376176 :         values[0] = psprintf("%u", multi->members[multi->iter].xid);
      82      376176 :         values[1] = mxstatus_to_string(multi->members[multi->iter].status);
      83             : 
      84      376176 :         tuple = BuildTupleFromCStrings(funccxt->attinmeta, values);
      85             : 
      86      376176 :         multi->iter++;
      87      376176 :         pfree(values[0]);
      88      376176 :         SRF_RETURN_NEXT(funccxt, HeapTupleGetDatum(tuple));
      89             :     }
      90             : 
      91       19980 :     SRF_RETURN_DONE(funccxt);
      92             : }
      93             : 
      94             : /*
      95             :  * pg_get_multixact_stats
      96             :  *
      97             :  * Returns statistics about current multixact usage.
      98             :  */
      99             : Datum
     100          24 : pg_get_multixact_stats(PG_FUNCTION_ARGS)
     101             : {
     102             :     TupleDesc   tupdesc;
     103             :     Datum       values[4];
     104             :     bool        nulls[4];
     105             :     uint64      members;
     106             :     MultiXactId oldestMultiXactId;
     107             :     uint32      multixacts;
     108             :     MultiXactOffset oldestOffset;
     109             :     MultiXactOffset nextOffset;
     110             :     uint64      membersBytes;
     111             : 
     112          24 :     if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
     113           0 :         ereport(ERROR,
     114             :                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
     115             :                  errmsg("return type must be a row type")));
     116             : 
     117          24 :     GetMultiXactInfo(&multixacts, &nextOffset, &oldestMultiXactId, &oldestOffset);
     118          24 :     members = nextOffset - oldestOffset;
     119             : 
     120          24 :     membersBytes = MultiXactOffsetStorageSize(nextOffset, oldestOffset);
     121             : 
     122          24 :     if (!has_privs_of_role(GetUserId(), ROLE_PG_READ_ALL_STATS))
     123             :     {
     124             :         /*
     125             :          * Only superusers and roles with privileges of pg_read_all_stats can
     126             :          * see details.
     127             :          */
     128           6 :         memset(nulls, true, sizeof(bool) * tupdesc->natts);
     129             :     }
     130             :     else
     131             :     {
     132          18 :         values[0] = UInt32GetDatum(multixacts);
     133          18 :         values[1] = Int64GetDatum(members);
     134          18 :         values[2] = Int64GetDatum(membersBytes);
     135          18 :         values[3] = UInt32GetDatum(oldestMultiXactId);
     136          18 :         memset(nulls, false, sizeof(nulls));
     137             :     }
     138             : 
     139          24 :     return HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls));
     140             : }