LCOV - code coverage report
Current view: top level - src/backend/partitioning - partdesc.c (source / functions) Hit Total Coverage
Test: PostgreSQL 18devel Lines: 108 126 85.7 %
Date: 2024-10-10 04:14:55 Functions: 6 6 100.0 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * partdesc.c
       4             :  *      Support routines for manipulating partition descriptors
       5             :  *
       6             :  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
       7             :  * Portions Copyright (c) 1994, Regents of the University of California
       8             :  *
       9             :  * IDENTIFICATION
      10             :  *        src/backend/partitioning/partdesc.c
      11             :  *
      12             :  *-------------------------------------------------------------------------
      13             :  */
      14             : 
      15             : #include "postgres.h"
      16             : 
      17             : #include "access/genam.h"
      18             : #include "access/htup_details.h"
      19             : #include "access/table.h"
      20             : #include "catalog/partition.h"
      21             : #include "catalog/pg_inherits.h"
      22             : #include "partitioning/partbounds.h"
      23             : #include "partitioning/partdesc.h"
      24             : #include "utils/builtins.h"
      25             : #include "utils/fmgroids.h"
      26             : #include "utils/hsearch.h"
      27             : #include "utils/inval.h"
      28             : #include "utils/lsyscache.h"
      29             : #include "utils/memutils.h"
      30             : #include "utils/partcache.h"
      31             : #include "utils/rel.h"
      32             : #include "utils/snapmgr.h"
      33             : #include "utils/syscache.h"
      34             : 
      35             : typedef struct PartitionDirectoryData
      36             : {
      37             :     MemoryContext pdir_mcxt;
      38             :     HTAB       *pdir_hash;
      39             :     bool        omit_detached;
      40             : }           PartitionDirectoryData;
      41             : 
      42             : typedef struct PartitionDirectoryEntry
      43             : {
      44             :     Oid         reloid;
      45             :     Relation    rel;
      46             :     PartitionDesc pd;
      47             : } PartitionDirectoryEntry;
      48             : 
      49             : static PartitionDesc RelationBuildPartitionDesc(Relation rel,
      50             :                                                 bool omit_detached);
      51             : 
      52             : 
      53             : /*
      54             :  * RelationGetPartitionDesc -- get partition descriptor, if relation is partitioned
      55             :  *
      56             :  * We keep two partdescs in relcache: rd_partdesc includes all partitions
      57             :  * (even those being concurrently marked detached), while rd_partdesc_nodetached
      58             :  * omits (some of) those.  We store the pg_inherits.xmin value for the latter,
      59             :  * to determine whether it can be validly reused in each case, since that
      60             :  * depends on the active snapshot.
      61             :  *
      62             :  * Note: we arrange for partition descriptors to not get freed until the
      63             :  * relcache entry's refcount goes to zero (see hacks in RelationClose,
      64             :  * RelationClearRelation, and RelationBuildPartitionDesc).  Therefore, even
      65             :  * though we hand back a direct pointer into the relcache entry, it's safe
      66             :  * for callers to continue to use that pointer as long as (a) they hold the
      67             :  * relation open, and (b) they hold a relation lock strong enough to ensure
      68             :  * that the data doesn't become stale.
      69             :  */
      70             : PartitionDesc
      71       58900 : RelationGetPartitionDesc(Relation rel, bool omit_detached)
      72             : {
      73             :     Assert(rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE);
      74             : 
      75             :     /*
      76             :      * If relcache has a partition descriptor, use that.  However, we can only
      77             :      * do so when we are asked to include all partitions including detached;
      78             :      * and also when we know that there are no detached partitions.
      79             :      *
      80             :      * If there is no active snapshot, detached partitions aren't omitted
      81             :      * either, so we can use the cached descriptor too in that case.
      82             :      */
      83       58900 :     if (likely(rel->rd_partdesc &&
      84             :                (!rel->rd_partdesc->detached_exist || !omit_detached ||
      85             :                 !ActiveSnapshotSet())))
      86       38068 :         return rel->rd_partdesc;
      87             : 
      88             :     /*
      89             :      * If we're asked to omit detached partitions, we may be able to use a
      90             :      * cached descriptor too.  We determine that based on the pg_inherits.xmin
      91             :      * that was saved alongside that descriptor: if the xmin that was not in
      92             :      * progress for that active snapshot is also not in progress for the
      93             :      * current active snapshot, then we can use it.  Otherwise build one from
      94             :      * scratch.
      95             :      */
      96       20832 :     if (omit_detached &&
      97       20278 :         rel->rd_partdesc_nodetached &&
      98          14 :         ActiveSnapshotSet())
      99             :     {
     100             :         Snapshot    activesnap;
     101             : 
     102             :         Assert(TransactionIdIsValid(rel->rd_partdesc_nodetached_xmin));
     103          14 :         activesnap = GetActiveSnapshot();
     104             : 
     105          14 :         if (!XidInMVCCSnapshot(rel->rd_partdesc_nodetached_xmin, activesnap))
     106          14 :             return rel->rd_partdesc_nodetached;
     107             :     }
     108             : 
     109       20818 :     return RelationBuildPartitionDesc(rel, omit_detached);
     110             : }
     111             : 
     112             : /*
     113             :  * RelationBuildPartitionDesc
     114             :  *      Form rel's partition descriptor, and store in relcache entry
     115             :  *
     116             :  * Partition descriptor is a complex structure; to avoid complicated logic to
     117             :  * free individual elements whenever the relcache entry is flushed, we give it
     118             :  * its own memory context, a child of CacheMemoryContext, which can easily be
     119             :  * deleted on its own.  To avoid leaking memory in that context in case of an
     120             :  * error partway through this function, the context is initially created as a
     121             :  * child of CurTransactionContext and only re-parented to CacheMemoryContext
     122             :  * at the end, when no further errors are possible.  Also, we don't make this
     123             :  * context the current context except in very brief code sections, out of fear
     124             :  * that some of our callees allocate memory on their own which would be leaked
     125             :  * permanently.
     126             :  *
     127             :  * As a special case, partition descriptors that are requested to omit
     128             :  * partitions being detached (and which contain such partitions) are transient
     129             :  * and are not associated with the relcache entry.  Such descriptors only last
     130             :  * through the requesting Portal, so we use the corresponding memory context
     131             :  * for them.
     132             :  */
     133             : static PartitionDesc
     134       20818 : RelationBuildPartitionDesc(Relation rel, bool omit_detached)
     135             : {
     136             :     PartitionDesc partdesc;
     137       20818 :     PartitionBoundInfo boundinfo = NULL;
     138             :     List       *inhoids;
     139       20818 :     PartitionBoundSpec **boundspecs = NULL;
     140       20818 :     Oid        *oids = NULL;
     141       20818 :     bool       *is_leaf = NULL;
     142             :     bool        detached_exist;
     143             :     bool        is_omit;
     144             :     TransactionId detached_xmin;
     145             :     ListCell   *cell;
     146             :     int         i,
     147             :                 nparts;
     148       20818 :     bool        retried = false;
     149       20818 :     PartitionKey key = RelationGetPartitionKey(rel);
     150             :     MemoryContext new_pdcxt;
     151             :     MemoryContext oldcxt;
     152             :     int        *mapping;
     153             : 
     154       20818 : retry:
     155             : 
     156             :     /*
     157             :      * Get partition oids from pg_inherits.  This uses a single snapshot to
     158             :      * fetch the list of children, so while more children may be getting added
     159             :      * or removed concurrently, whatever this function returns will be
     160             :      * accurate as of some well-defined point in time.
     161             :      */
     162       20818 :     detached_exist = false;
     163       20818 :     detached_xmin = InvalidTransactionId;
     164       20818 :     inhoids = find_inheritance_children_extended(RelationGetRelid(rel),
     165             :                                                  omit_detached, NoLock,
     166             :                                                  &detached_exist,
     167             :                                                  &detached_xmin);
     168             : 
     169       20818 :     nparts = list_length(inhoids);
     170             : 
     171             :     /* Allocate working arrays for OIDs, leaf flags, and boundspecs. */
     172       20818 :     if (nparts > 0)
     173             :     {
     174       15294 :         oids = (Oid *) palloc(nparts * sizeof(Oid));
     175       15294 :         is_leaf = (bool *) palloc(nparts * sizeof(bool));
     176       15294 :         boundspecs = palloc(nparts * sizeof(PartitionBoundSpec *));
     177             :     }
     178             : 
     179             :     /* Collect bound spec nodes for each partition. */
     180       20818 :     i = 0;
     181       51340 :     foreach(cell, inhoids)
     182             :     {
     183       30522 :         Oid         inhrelid = lfirst_oid(cell);
     184             :         HeapTuple   tuple;
     185       30522 :         PartitionBoundSpec *boundspec = NULL;
     186             : 
     187             :         /* Try fetching the tuple from the catcache, for speed. */
     188       30522 :         tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(inhrelid));
     189       30522 :         if (HeapTupleIsValid(tuple))
     190             :         {
     191             :             Datum       datum;
     192             :             bool        isnull;
     193             : 
     194       30522 :             datum = SysCacheGetAttr(RELOID, tuple,
     195             :                                     Anum_pg_class_relpartbound,
     196             :                                     &isnull);
     197       30522 :             if (!isnull)
     198       30522 :                 boundspec = stringToNode(TextDatumGetCString(datum));
     199       30522 :             ReleaseSysCache(tuple);
     200             :         }
     201             : 
     202             :         /*
     203             :          * Two problems are possible here.  First, a concurrent ATTACH
     204             :          * PARTITION might be in the process of adding a new partition, but
     205             :          * the syscache doesn't have it, or its copy of it does not yet have
     206             :          * its relpartbound set.  We cannot just AcceptInvalidationMessages(),
     207             :          * because the other process might have already removed itself from
     208             :          * the ProcArray but not yet added its invalidation messages to the
     209             :          * shared queue.  We solve this problem by reading pg_class directly
     210             :          * for the desired tuple.
     211             :          *
     212             :          * If the partition recently detached is also dropped, we get no tuple
     213             :          * from the scan.  In that case, we also retry, and next time through
     214             :          * here, we don't see that partition anymore.
     215             :          *
     216             :          * The other problem is that DETACH CONCURRENTLY is in the process of
     217             :          * removing a partition, which happens in two steps: first it marks it
     218             :          * as "detach pending", commits, then unsets relpartbound.  If
     219             :          * find_inheritance_children_extended included that partition but we
     220             :          * below we see that DETACH CONCURRENTLY has reset relpartbound for
     221             :          * it, we'd see an inconsistent view.  (The inconsistency is seen
     222             :          * because table_open below reads invalidation messages.)  We protect
     223             :          * against this by retrying find_inheritance_children_extended().
     224             :          */
     225       30522 :         if (boundspec == NULL)
     226             :         {
     227             :             Relation    pg_class;
     228             :             SysScanDesc scan;
     229             :             ScanKeyData key[1];
     230             : 
     231           0 :             pg_class = table_open(RelationRelationId, AccessShareLock);
     232           0 :             ScanKeyInit(&key[0],
     233             :                         Anum_pg_class_oid,
     234             :                         BTEqualStrategyNumber, F_OIDEQ,
     235             :                         ObjectIdGetDatum(inhrelid));
     236           0 :             scan = systable_beginscan(pg_class, ClassOidIndexId, true,
     237             :                                       NULL, 1, key);
     238             : 
     239             :             /*
     240             :              * We could get one tuple from the scan (the normal case), or zero
     241             :              * tuples if the table has been dropped meanwhile.
     242             :              */
     243           0 :             tuple = systable_getnext(scan);
     244           0 :             if (HeapTupleIsValid(tuple))
     245             :             {
     246             :                 Datum       datum;
     247             :                 bool        isnull;
     248             : 
     249           0 :                 datum = heap_getattr(tuple, Anum_pg_class_relpartbound,
     250             :                                      RelationGetDescr(pg_class), &isnull);
     251           0 :                 if (!isnull)
     252           0 :                     boundspec = stringToNode(TextDatumGetCString(datum));
     253             :             }
     254           0 :             systable_endscan(scan);
     255           0 :             table_close(pg_class, AccessShareLock);
     256             : 
     257             :             /*
     258             :              * If we still don't get a relpartbound value (either because
     259             :              * boundspec is null or because there was no tuple), then it must
     260             :              * be because of DETACH CONCURRENTLY.  Restart from the top, as
     261             :              * explained above.  We only do this once, for two reasons: first,
     262             :              * only one DETACH CONCURRENTLY session could affect us at a time,
     263             :              * since each of them would have to wait for the snapshot under
     264             :              * which this is running; and second, to avoid possible infinite
     265             :              * loops in case of catalog corruption.
     266             :              *
     267             :              * Note that the current memory context is short-lived enough, so
     268             :              * we needn't worry about memory leaks here.
     269             :              */
     270           0 :             if (!boundspec && !retried)
     271             :             {
     272           0 :                 AcceptInvalidationMessages();
     273           0 :                 retried = true;
     274           0 :                 goto retry;
     275             :             }
     276             :         }
     277             : 
     278             :         /* Sanity checks. */
     279       30522 :         if (!boundspec)
     280           0 :             elog(ERROR, "missing relpartbound for relation %u", inhrelid);
     281       30522 :         if (!IsA(boundspec, PartitionBoundSpec))
     282           0 :             elog(ERROR, "invalid relpartbound for relation %u", inhrelid);
     283             : 
     284             :         /*
     285             :          * If the PartitionBoundSpec says this is the default partition, its
     286             :          * OID should match pg_partitioned_table.partdefid; if not, the
     287             :          * catalog is corrupt.
     288             :          */
     289       30522 :         if (boundspec->is_default)
     290             :         {
     291             :             Oid         partdefid;
     292             : 
     293        1658 :             partdefid = get_default_partition_oid(RelationGetRelid(rel));
     294        1658 :             if (partdefid != inhrelid)
     295           0 :                 elog(ERROR, "expected partdefid %u, but got %u",
     296             :                      inhrelid, partdefid);
     297             :         }
     298             : 
     299             :         /* Save results. */
     300       30522 :         oids[i] = inhrelid;
     301       30522 :         is_leaf[i] = (get_rel_relkind(inhrelid) != RELKIND_PARTITIONED_TABLE);
     302       30522 :         boundspecs[i] = boundspec;
     303       30522 :         ++i;
     304             :     }
     305             : 
     306             :     /*
     307             :      * Create PartitionBoundInfo and mapping, working in the caller's context.
     308             :      * This could fail, but we haven't done any damage if so.
     309             :      */
     310       20818 :     if (nparts > 0)
     311       15294 :         boundinfo = partition_bounds_create(boundspecs, nparts, key, &mapping);
     312             : 
     313             :     /*
     314             :      * Now build the actual relcache partition descriptor, copying all the
     315             :      * data into a new, small context.  As per above comment, we don't make
     316             :      * this a long-lived context until it's finished.
     317             :      */
     318       20818 :     new_pdcxt = AllocSetContextCreate(CurTransactionContext,
     319             :                                       "partition descriptor",
     320             :                                       ALLOCSET_SMALL_SIZES);
     321       20818 :     MemoryContextCopyAndSetIdentifier(new_pdcxt,
     322             :                                       RelationGetRelationName(rel));
     323             : 
     324             :     partdesc = (PartitionDescData *)
     325       20818 :         MemoryContextAllocZero(new_pdcxt, sizeof(PartitionDescData));
     326       20818 :     partdesc->nparts = nparts;
     327       20818 :     partdesc->detached_exist = detached_exist;
     328             :     /* If there are no partitions, the rest of the partdesc can stay zero */
     329       20818 :     if (nparts > 0)
     330             :     {
     331       15294 :         oldcxt = MemoryContextSwitchTo(new_pdcxt);
     332       15294 :         partdesc->boundinfo = partition_bounds_copy(boundinfo, key);
     333             : 
     334             :         /* Initialize caching fields for speeding up ExecFindPartition */
     335       15294 :         partdesc->last_found_datum_index = -1;
     336       15294 :         partdesc->last_found_part_index = -1;
     337       15294 :         partdesc->last_found_count = 0;
     338             : 
     339       15294 :         partdesc->oids = (Oid *) palloc(nparts * sizeof(Oid));
     340       15294 :         partdesc->is_leaf = (bool *) palloc(nparts * sizeof(bool));
     341             : 
     342             :         /*
     343             :          * Assign OIDs from the original array into mapped indexes of the
     344             :          * result array.  The order of OIDs in the former is defined by the
     345             :          * catalog scan that retrieved them, whereas that in the latter is
     346             :          * defined by canonicalized representation of the partition bounds.
     347             :          * Also save leaf-ness of each partition.
     348             :          */
     349       45816 :         for (i = 0; i < nparts; i++)
     350             :         {
     351       30522 :             int         index = mapping[i];
     352             : 
     353       30522 :             partdesc->oids[index] = oids[i];
     354       30522 :             partdesc->is_leaf[index] = is_leaf[i];
     355             :         }
     356       15294 :         MemoryContextSwitchTo(oldcxt);
     357             :     }
     358             : 
     359             :     /*
     360             :      * Are we working with the partdesc that omits the detached partition, or
     361             :      * the one that includes it?
     362             :      *
     363             :      * Note that if a partition was found by the catalog's scan to have been
     364             :      * detached, but the pg_inherit tuple saying so was not visible to the
     365             :      * active snapshot (find_inheritance_children_extended will not have set
     366             :      * detached_xmin in that case), we consider there to be no "omittable"
     367             :      * detached partitions.
     368             :      */
     369       20908 :     is_omit = omit_detached && detached_exist && ActiveSnapshotSet() &&
     370          90 :         TransactionIdIsValid(detached_xmin);
     371             : 
     372             :     /*
     373             :      * We have a fully valid partdesc.  Reparent it so that it has the right
     374             :      * lifespan.
     375             :      */
     376       20818 :     MemoryContextSetParent(new_pdcxt, CacheMemoryContext);
     377             : 
     378             :     /*
     379             :      * Store it into relcache.
     380             :      *
     381             :      * But first, a kluge: if there's an old context for this type of
     382             :      * descriptor, it contains an old partition descriptor that may still be
     383             :      * referenced somewhere.  Preserve it, while not leaking it, by
     384             :      * reattaching it as a child context of the new one.  Eventually it will
     385             :      * get dropped by either RelationClose or RelationClearRelation. (We keep
     386             :      * the regular partdesc in rd_pdcxt, and the partdesc-excluding-
     387             :      * detached-partitions in rd_pddcxt.)
     388             :      */
     389       20818 :     if (is_omit)
     390             :     {
     391          66 :         if (rel->rd_pddcxt != NULL)
     392           0 :             MemoryContextSetParent(rel->rd_pddcxt, new_pdcxt);
     393          66 :         rel->rd_pddcxt = new_pdcxt;
     394          66 :         rel->rd_partdesc_nodetached = partdesc;
     395             : 
     396             :         /*
     397             :          * For partdescs built excluding detached partitions, which we save
     398             :          * separately, we also record the pg_inherits.xmin of the detached
     399             :          * partition that was omitted; this informs a future potential user of
     400             :          * such a cached partdesc to only use it after cross-checking that the
     401             :          * xmin is indeed visible to the snapshot it is going to be working
     402             :          * with.
     403             :          */
     404             :         Assert(TransactionIdIsValid(detached_xmin));
     405          66 :         rel->rd_partdesc_nodetached_xmin = detached_xmin;
     406             :     }
     407             :     else
     408             :     {
     409       20752 :         if (rel->rd_pdcxt != NULL)
     410        4626 :             MemoryContextSetParent(rel->rd_pdcxt, new_pdcxt);
     411       20752 :         rel->rd_pdcxt = new_pdcxt;
     412       20752 :         rel->rd_partdesc = partdesc;
     413             :     }
     414             : 
     415       20818 :     return partdesc;
     416             : }
     417             : 
     418             : /*
     419             :  * CreatePartitionDirectory
     420             :  *      Create a new partition directory object.
     421             :  */
     422             : PartitionDirectory
     423       18570 : CreatePartitionDirectory(MemoryContext mcxt, bool omit_detached)
     424             : {
     425       18570 :     MemoryContext oldcontext = MemoryContextSwitchTo(mcxt);
     426             :     PartitionDirectory pdir;
     427             :     HASHCTL     ctl;
     428             : 
     429       18570 :     pdir = palloc(sizeof(PartitionDirectoryData));
     430       18570 :     pdir->pdir_mcxt = mcxt;
     431             : 
     432       18570 :     ctl.keysize = sizeof(Oid);
     433       18570 :     ctl.entrysize = sizeof(PartitionDirectoryEntry);
     434       18570 :     ctl.hcxt = mcxt;
     435             : 
     436       18570 :     pdir->pdir_hash = hash_create("partition directory", 256, &ctl,
     437             :                                   HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
     438       18570 :     pdir->omit_detached = omit_detached;
     439             : 
     440       18570 :     MemoryContextSwitchTo(oldcontext);
     441       18570 :     return pdir;
     442             : }
     443             : 
     444             : /*
     445             :  * PartitionDirectoryLookup
     446             :  *      Look up the partition descriptor for a relation in the directory.
     447             :  *
     448             :  * The purpose of this function is to ensure that we get the same
     449             :  * PartitionDesc for each relation every time we look it up.  In the
     450             :  * face of concurrent DDL, different PartitionDescs may be constructed with
     451             :  * different views of the catalog state, but any single particular OID
     452             :  * will always get the same PartitionDesc for as long as the same
     453             :  * PartitionDirectory is used.
     454             :  */
     455             : PartitionDesc
     456       41864 : PartitionDirectoryLookup(PartitionDirectory pdir, Relation rel)
     457             : {
     458             :     PartitionDirectoryEntry *pde;
     459       41864 :     Oid         relid = RelationGetRelid(rel);
     460             :     bool        found;
     461             : 
     462       41864 :     pde = hash_search(pdir->pdir_hash, &relid, HASH_ENTER, &found);
     463       41864 :     if (!found)
     464             :     {
     465             :         /*
     466             :          * We must keep a reference count on the relation so that the
     467             :          * PartitionDesc to which we are pointing can't get destroyed.
     468             :          */
     469       25170 :         RelationIncrementReferenceCount(rel);
     470       25170 :         pde->rel = rel;
     471       25170 :         pde->pd = RelationGetPartitionDesc(rel, pdir->omit_detached);
     472             :         Assert(pde->pd != NULL);
     473             :     }
     474       41864 :     return pde->pd;
     475             : }
     476             : 
     477             : /*
     478             :  * DestroyPartitionDirectory
     479             :  *      Destroy a partition directory.
     480             :  *
     481             :  * Release the reference counts we're holding.
     482             :  */
     483             : void
     484       17846 : DestroyPartitionDirectory(PartitionDirectory pdir)
     485             : {
     486             :     HASH_SEQ_STATUS status;
     487             :     PartitionDirectoryEntry *pde;
     488             : 
     489       17846 :     hash_seq_init(&status, pdir->pdir_hash);
     490       42074 :     while ((pde = hash_seq_search(&status)) != NULL)
     491       24228 :         RelationDecrementReferenceCount(pde->rel);
     492       17846 : }
     493             : 
     494             : /*
     495             :  * get_default_oid_from_partdesc
     496             :  *
     497             :  * Given a partition descriptor, return the OID of the default partition, if
     498             :  * one exists; else, return InvalidOid.
     499             :  */
     500             : Oid
     501       19426 : get_default_oid_from_partdesc(PartitionDesc partdesc)
     502             : {
     503       19426 :     if (partdesc && partdesc->boundinfo &&
     504       11634 :         partition_bound_has_default(partdesc->boundinfo))
     505        1310 :         return partdesc->oids[partdesc->boundinfo->default_index];
     506             : 
     507       18116 :     return InvalidOid;
     508             : }

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