Line data    Source code

       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * partitionfuncs.c
       4             :  *    Functions for accessing partition-related metadata
       5             :  *
       6             :  * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
       7             :  * Portions Copyright (c) 1994, Regents of the University of California
       8             :  *
       9             :  *
      10             :  * IDENTIFICATION
      11             :  *    src/backend/utils/adt/partitionfuncs.c
      12             :  *
      13             :  *-------------------------------------------------------------------------
      14             :  */
      15             : 
      16             : #include "postgres.h"
      17             : 
      18             : #include "access/htup_details.h"
      19             : #include "catalog/partition.h"
      20             : #include "catalog/pg_class.h"
      21             : #include "catalog/pg_inherits.h"
      22             : #include "funcapi.h"
      23             : #include "utils/fmgrprotos.h"
      24             : #include "utils/lsyscache.h"
      25             : #include "utils/syscache.h"
      26             : 
      27             : /*
      28             :  * Checks if a given relation can be part of a partition tree.  Returns
      29             :  * false if the relation cannot be processed, in which case it is up to
      30             :  * the caller to decide what to do, by either raising an error or doing
      31             :  * something else.
      32             :  */
      33             : static bool
      34       12098 : check_rel_can_be_partition(Oid relid)
      35             : {
      36             :     char        relkind;
      37             :     bool        relispartition;
      38             : 
      39             :     /* Check if relation exists */
      40       12098 :     if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(relid)))
      41          18 :         return false;
      42             : 
      43       12080 :     relkind = get_rel_relkind(relid);
      44       12080 :     relispartition = get_rel_relispartition(relid);
      45             : 
      46             :     /* Only allow relation types that can appear in partition trees. */
      47       12080 :     if (!relispartition && !RELKIND_HAS_PARTITIONS(relkind))
      48        7646 :         return false;
      49             : 
      50        4434 :     return true;
      51             : }
      52             : 
      53             : /*
      54             :  * pg_partition_tree
      55             :  *
      56             :  * Produce a view with one row per member of a partition tree, beginning
      57             :  * from the top-most parent given by the caller.  This gives information
      58             :  * about each partition, its immediate partitioned parent, if it is
      59             :  * a leaf partition and its level in the hierarchy.
      60             :  */
      61             : Datum
      62        1098 : pg_partition_tree(PG_FUNCTION_ARGS)
      63             : {
      64             : #define PG_PARTITION_TREE_COLS  4
      65        1098 :     Oid         rootrelid = PG_GETARG_OID(0);
      66             :     FuncCallContext *funcctx;
      67             :     List       *partitions;
      68             : 
      69             :     /* stuff done only on the first call of the function */
      70        1098 :     if (SRF_IS_FIRSTCALL())
      71             :     {
      72             :         MemoryContext oldcxt;
      73             :         TupleDesc   tupdesc;
      74             : 
      75             :         /* create a function context for cross-call persistence */
      76         238 :         funcctx = SRF_FIRSTCALL_INIT();
      77             : 
      78         238 :         if (!check_rel_can_be_partition(rootrelid))
      79          50 :             SRF_RETURN_DONE(funcctx);
      80             : 
      81             :         /* switch to memory context appropriate for multiple function calls */
      82         188 :         oldcxt = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
      83             : 
      84             :         /*
      85             :          * Find all members of inheritance set.  We only need AccessShareLock
      86             :          * on the children for the partition information lookup.
      87             :          */
      88         188 :         partitions = find_all_inheritors(rootrelid, AccessShareLock, NULL);
      89             : 
      90         188 :         if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
      91           0 :             elog(ERROR, "return type must be a row type");
      92         188 :         funcctx->tuple_desc = tupdesc;
      93             : 
      94             :         /* The only state we need is the partition list */
      95         188 :         funcctx->user_fctx = partitions;
      96             : 
      97         188 :         MemoryContextSwitchTo(oldcxt);
      98             :     }
      99             : 
     100             :     /* stuff done on every call of the function */
     101        1048 :     funcctx = SRF_PERCALL_SETUP();
     102        1048 :     partitions = (List *) funcctx->user_fctx;
     103             : 
     104        1048 :     if (funcctx->call_cntr < list_length(partitions))
     105             :     {
     106             :         Datum       result;
     107         860 :         Datum       values[PG_PARTITION_TREE_COLS] = {0};
     108         860 :         bool        nulls[PG_PARTITION_TREE_COLS] = {0};
     109             :         HeapTuple   tuple;
     110         860 :         Oid         parentid = InvalidOid;
     111         860 :         Oid         relid = list_nth_oid(partitions, funcctx->call_cntr);
     112         860 :         char        relkind = get_rel_relkind(relid);
     113         860 :         int         level = 0;
     114         860 :         List       *ancestors = get_partition_ancestors(relid);
     115             :         ListCell   *lc;
     116             : 
     117             :         /*
     118             :          * Form tuple with appropriate data.
     119             :          */
     120             : 
     121             :         /* relid */
     122         860 :         values[0] = ObjectIdGetDatum(relid);
     123             : 
     124             :         /* parentid */
     125         860 :         if (ancestors != NIL)
     126         712 :             parentid = linitial_oid(ancestors);
     127         860 :         if (OidIsValid(parentid))
     128         712 :             values[1] = ObjectIdGetDatum(parentid);
     129             :         else
     130         148 :             nulls[1] = true;
     131             : 
     132             :         /* isleaf */
     133         860 :         values[2] = BoolGetDatum(!RELKIND_HAS_PARTITIONS(relkind));
     134             : 
     135             :         /* level */
     136         860 :         if (relid != rootrelid)
     137             :         {
     138         954 :             foreach(lc, ancestors)
     139             :             {
     140         954 :                 level++;
     141         954 :                 if (lfirst_oid(lc) == rootrelid)
     142         672 :                     break;
     143             :             }
     144             :         }
     145         860 :         values[3] = Int32GetDatum(level);
     146             : 
     147         860 :         tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
     148         860 :         result = HeapTupleGetDatum(tuple);
     149         860 :         SRF_RETURN_NEXT(funcctx, result);
     150             :     }
     151             : 
     152             :     /* done when there are no more elements left */
     153         188 :     SRF_RETURN_DONE(funcctx);
     154             : }
     155             : 
     156             : /*
     157             :  * pg_partition_root
     158             :  *
     159             :  * Returns the top-most parent of the partition tree to which a given
     160             :  * relation belongs, or NULL if it's not (or cannot be) part of any
     161             :  * partition tree.
     162             :  */
     163             : Datum
     164          96 : pg_partition_root(PG_FUNCTION_ARGS)
     165             : {
     166          96 :     Oid         relid = PG_GETARG_OID(0);
     167             :     Oid         rootrelid;
     168             :     List       *ancestors;
     169             : 
     170          96 :     if (!check_rel_can_be_partition(relid))
     171          36 :         PG_RETURN_NULL();
     172             : 
     173             :     /* fetch the list of ancestors */
     174          60 :     ancestors = get_partition_ancestors(relid);
     175             : 
     176             :     /*
     177             :      * If the input relation is already the top-most parent, just return
     178             :      * itself.
     179             :      */
     180          60 :     if (ancestors == NIL)
     181          12 :         PG_RETURN_OID(relid);
     182             : 
     183          48 :     rootrelid = llast_oid(ancestors);
     184          48 :     list_free(ancestors);
     185             : 
     186             :     /*
     187             :      * "rootrelid" must contain a valid OID, given that the input relation is
     188             :      * a valid partition tree member as checked above.
     189             :      */
     190             :     Assert(OidIsValid(rootrelid));
     191          48 :     PG_RETURN_OID(rootrelid);
     192             : }
     193             : 
     194             : /*
     195             :  * pg_partition_ancestors
     196             :  *
     197             :  * Produces a view with one row per ancestor of the given partition,
     198             :  * including the input relation itself.
     199             :  */
     200             : Datum
     201       19314 : pg_partition_ancestors(PG_FUNCTION_ARGS)
     202             : {
     203       19314 :     Oid         relid = PG_GETARG_OID(0);
     204             :     FuncCallContext *funcctx;
     205             :     List       *ancestors;
     206             : 
     207       19314 :     if (SRF_IS_FIRSTCALL())
     208             :     {
     209             :         MemoryContext oldcxt;
     210             : 
     211       11764 :         funcctx = SRF_FIRSTCALL_INIT();
     212             : 
     213       11764 :         if (!check_rel_can_be_partition(relid))
     214        7578 :             SRF_RETURN_DONE(funcctx);
     215             : 
     216        4186 :         oldcxt = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
     217             : 
     218        4186 :         ancestors = get_partition_ancestors(relid);
     219        4186 :         ancestors = lcons_oid(relid, ancestors);
     220             : 
     221             :         /* The only state we need is the ancestors list */
     222        4186 :         funcctx->user_fctx = ancestors;
     223             : 
     224        4186 :         MemoryContextSwitchTo(oldcxt);
     225             :     }
     226             : 
     227       11736 :     funcctx = SRF_PERCALL_SETUP();
     228       11736 :     ancestors = (List *) funcctx->user_fctx;
     229             : 
     230       11736 :     if (funcctx->call_cntr < list_length(ancestors))
     231             :     {
     232        7550 :         Oid         resultrel = list_nth_oid(ancestors, funcctx->call_cntr);
     233             : 
     234        7550 :         SRF_RETURN_NEXT(funcctx, ObjectIdGetDatum(resultrel));
     235             :     }
     236             : 
     237        4186 :     SRF_RETURN_DONE(funcctx);
     238             : }