partdesc.c

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/*-------------------------------------------------------------------------
 *
 * partdesc.c
 *      Support routines for manipulating partition descriptors
 *
 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *        src/backend/partitioning/partdesc.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/genam.h"
#include "access/htup_details.h"
#include "access/table.h"
#include "catalog/indexing.h"
#include "catalog/partition.h"
#include "catalog/pg_inherits.h"
#include "partitioning/partbounds.h"
#include "partitioning/partdesc.h"
#include "storage/bufmgr.h"
#include "storage/sinval.h"
#include "utils/builtins.h"
#include "utils/inval.h"
#include "utils/fmgroids.h"
#include "utils/hsearch.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/partcache.h"
#include "utils/syscache.h"

typedef struct PartitionDirectoryData
{
    MemoryContext pdir_mcxt;
    HTAB       *pdir_hash;
}           PartitionDirectoryData;

typedef struct PartitionDirectoryEntry
{
    Oid         reloid;
    Relation    rel;
    PartitionDesc pd;
} PartitionDirectoryEntry;

/*
 * RelationBuildPartitionDesc
 *      Form rel's partition descriptor, and store in relcache entry
 *
 * Note: the descriptor won't be flushed from the cache by
 * RelationClearRelation() unless it's changed because of
 * addition or removal of a partition.  Hence, code holding a lock
 * that's sufficient to prevent that can assume that rd_partdesc
 * won't change underneath it.
 */
void
RelationBuildPartitionDesc(Relation rel)
{
    PartitionDesc partdesc;
    PartitionBoundInfo boundinfo = NULL;
    List       *inhoids;
    PartitionBoundSpec **boundspecs = NULL;
    Oid        *oids = NULL;
    ListCell   *cell;
    int         i,
                nparts;
    PartitionKey key = RelationGetPartitionKey(rel);
    MemoryContext oldcxt;
    int        *mapping;

    /*
     * Get partition oids from pg_inherits.  This uses a single snapshot to
     * fetch the list of children, so while more children may be getting added
     * concurrently, whatever this function returns will be accurate as of
     * some well-defined point in time.
     */
    inhoids = find_inheritance_children(RelationGetRelid(rel), NoLock);
    nparts = list_length(inhoids);

    /* Allocate arrays for OIDs and boundspecs. */
    if (nparts > 0)
    {
        oids = palloc(nparts * sizeof(Oid));
        boundspecs = palloc(nparts * sizeof(PartitionBoundSpec *));
    }

    /* Collect bound spec nodes for each partition. */
    i = 0;
    foreach(cell, inhoids)
    {
        Oid         inhrelid = lfirst_oid(cell);
        HeapTuple   tuple;
        PartitionBoundSpec *boundspec = NULL;

        /* Try fetching the tuple from the catcache, for speed. */
        tuple = SearchSysCache1(RELOID, inhrelid);
        if (HeapTupleIsValid(tuple))
        {
            Datum       datum;
            bool        isnull;

            datum = SysCacheGetAttr(RELOID, tuple,
                                    Anum_pg_class_relpartbound,
                                    &isnull);
            if (!isnull)
                boundspec = stringToNode(TextDatumGetCString(datum));
            ReleaseSysCache(tuple);
        }

        /*
         * The system cache may be out of date; if so, we may find no pg_class
         * tuple or an old one where relpartbound is NULL.  In that case, try
         * the table directly.  We can't just AcceptInvalidationMessages() and
         * retry the system cache lookup because it's possible that a
         * concurrent ATTACH PARTITION operation has removed itself to the
         * ProcArray but yet added invalidation messages to the shared queue;
         * InvalidateSystemCaches() would work, but seems excessive.
         *
         * Note that this algorithm assumes that PartitionBoundSpec we manage
         * to fetch is the right one -- so this is only good enough for
         * concurrent ATTACH PARTITION, not concurrent DETACH PARTITION or
         * some hypothetical operation that changes the partition bounds.
         */
        if (boundspec == NULL)
        {
            Relation    pg_class;
            SysScanDesc scan;
            ScanKeyData key[1];
            Datum       datum;
            bool        isnull;

            pg_class = table_open(RelationRelationId, AccessShareLock);
            ScanKeyInit(&key[0],
                        Anum_pg_class_oid,
                        BTEqualStrategyNumber, F_OIDEQ,
                        ObjectIdGetDatum(inhrelid));
            scan = systable_beginscan(pg_class, ClassOidIndexId, true,
                                      NULL, 1, key);
            tuple = systable_getnext(scan);
            datum = heap_getattr(tuple, Anum_pg_class_relpartbound,
                                 RelationGetDescr(pg_class), &isnull);
            if (!isnull)
                boundspec = stringToNode(TextDatumGetCString(datum));
            systable_endscan(scan);
            table_close(pg_class, AccessShareLock);
        }

        /* Sanity checks. */
        if (!boundspec)
            elog(ERROR, "missing relpartbound for relation %u", inhrelid);
        if (!IsA(boundspec, PartitionBoundSpec))
            elog(ERROR, "invalid relpartbound for relation %u", inhrelid);

        /*
         * If the PartitionBoundSpec says this is the default partition, its
         * OID should match pg_partitioned_table.partdefid; if not, the
         * catalog is corrupt.
         */
        if (boundspec->is_default)
        {
            Oid         partdefid;

            partdefid = get_default_partition_oid(RelationGetRelid(rel));
            if (partdefid != inhrelid)
                elog(ERROR, "expected partdefid %u, but got %u",
                     inhrelid, partdefid);
        }

        /* Save results. */
        oids[i] = inhrelid;
        boundspecs[i] = boundspec;
        ++i;
    }

    /* Assert we aren't about to leak any old data structure */
    Assert(rel->rd_pdcxt == NULL);
    Assert(rel->rd_partdesc == NULL);

    /*
     * Now build the actual relcache partition descriptor.  Note that the
     * order of operations here is fairly critical.  If we fail partway
     * through this code, we won't have leaked memory because the rd_pdcxt is
     * attached to the relcache entry immediately, so it'll be freed whenever
     * the entry is rebuilt or destroyed.  However, we don't assign to
     * rd_partdesc until the cached data structure is fully complete and
     * valid, so that no other code might try to use it.
     */
    rel->rd_pdcxt = AllocSetContextCreate(CacheMemoryContext,
                                          "partition descriptor",
                                          ALLOCSET_SMALL_SIZES);
    MemoryContextCopyAndSetIdentifier(rel->rd_pdcxt,
                                      RelationGetRelationName(rel));

    partdesc = (PartitionDescData *)
        MemoryContextAllocZero(rel->rd_pdcxt, sizeof(PartitionDescData));
    partdesc->nparts = nparts;
    /* If there are no partitions, the rest of the partdesc can stay zero */
    if (nparts > 0)
    {
        /* Create PartitionBoundInfo, using the caller's context. */
        boundinfo = partition_bounds_create(boundspecs, nparts, key, &mapping);

        /* Now copy all info into relcache's partdesc. */
        oldcxt = MemoryContextSwitchTo(rel->rd_pdcxt);
        partdesc->boundinfo = partition_bounds_copy(boundinfo, key);
        partdesc->oids = (Oid *) palloc(nparts * sizeof(Oid));
        partdesc->is_leaf = (bool *) palloc(nparts * sizeof(bool));
        MemoryContextSwitchTo(oldcxt);

        /*
         * Assign OIDs from the original array into mapped indexes of the
         * result array.  The order of OIDs in the former is defined by the
         * catalog scan that retrieved them, whereas that in the latter is
         * defined by canonicalized representation of the partition bounds.
         *
         * Also record leaf-ness of each partition.  For this we use
         * get_rel_relkind() which may leak memory, so be sure to run it in
         * the caller's context.
         */
        for (i = 0; i < nparts; i++)
        {
            int         index = mapping[i];

            partdesc->oids[index] = oids[i];
            partdesc->is_leaf[index] =
                (get_rel_relkind(oids[i]) != RELKIND_PARTITIONED_TABLE);
        }
    }

    rel->rd_partdesc = partdesc;
}

/*
 * CreatePartitionDirectory
 *      Create a new partition directory object.
 */
PartitionDirectory
CreatePartitionDirectory(MemoryContext mcxt)
{
    MemoryContext oldcontext = MemoryContextSwitchTo(mcxt);
    PartitionDirectory pdir;
    HASHCTL     ctl;

    MemSet(&ctl, 0, sizeof(HASHCTL));
    ctl.keysize = sizeof(Oid);
    ctl.entrysize = sizeof(PartitionDirectoryEntry);
    ctl.hcxt = mcxt;

    pdir = palloc(sizeof(PartitionDirectoryData));
    pdir->pdir_mcxt = mcxt;
    pdir->pdir_hash = hash_create("partition directory", 256, &ctl,
                                  HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);

    MemoryContextSwitchTo(oldcontext);
    return pdir;
}

/*
 * PartitionDirectoryLookup
 *      Look up the partition descriptor for a relation in the directory.
 *
 * The purpose of this function is to ensure that we get the same
 * PartitionDesc for each relation every time we look it up.  In the
 * face of current DDL, different PartitionDescs may be constructed with
 * different views of the catalog state, but any single particular OID
 * will always get the same PartitionDesc for as long as the same
 * PartitionDirectory is used.
 */
PartitionDesc
PartitionDirectoryLookup(PartitionDirectory pdir, Relation rel)
{
    PartitionDirectoryEntry *pde;
    Oid         relid = RelationGetRelid(rel);
    bool        found;

    pde = hash_search(pdir->pdir_hash, &relid, HASH_ENTER, &found);
    if (!found)
    {
        /*
         * We must keep a reference count on the relation so that the
         * PartitionDesc to which we are pointing can't get destroyed.
         */
        RelationIncrementReferenceCount(rel);
        pde->rel = rel;
        pde->pd = RelationGetPartitionDesc(rel);
        Assert(pde->pd != NULL);
    }
    return pde->pd;
}

/*
 * DestroyPartitionDirectory
 *      Destroy a partition directory.
 *
 * Release the reference counts we're holding.
 */
void
DestroyPartitionDirectory(PartitionDirectory pdir)
{
    HASH_SEQ_STATUS status;
    PartitionDirectoryEntry *pde;

    hash_seq_init(&status, pdir->pdir_hash);
    while ((pde = hash_seq_search(&status)) != NULL)
        RelationDecrementReferenceCount(pde->rel);
}

/*
 * equalPartitionDescs
 *      Compare two partition descriptors for logical equality
 */
bool
equalPartitionDescs(PartitionKey key, PartitionDesc partdesc1,
                    PartitionDesc partdesc2)
{
    int         i;

    if (partdesc1 != NULL)
    {
        if (partdesc2 == NULL)
            return false;
        if (partdesc1->nparts != partdesc2->nparts)
            return false;

        Assert(key != NULL || partdesc1->nparts == 0);

        /*
         * Same oids? If the partitioning structure did not change, that is,
         * no partitions were added or removed to the relation, the oids array
         * should still match element-by-element.
         */
        for (i = 0; i < partdesc1->nparts; i++)
        {
            if (partdesc1->oids[i] != partdesc2->oids[i])
                return false;
        }

        /*
         * Now compare partition bound collections.  The logic to iterate over
         * the collections is private to partition.c.
         */
        if (partdesc1->boundinfo != NULL)
        {
            if (partdesc2->boundinfo == NULL)
                return false;

            if (!partition_bounds_equal(key->partnatts, key->parttyplen,
                                        key->parttypbyval,
                                        partdesc1->boundinfo,
                                        partdesc2->boundinfo))
                return false;
        }
        else if (partdesc2->boundinfo != NULL)
            return false;
    }
    else if (partdesc2 != NULL)
        return false;

    return true;
}

/*
 * get_default_oid_from_partdesc
 *
 * Given a partition descriptor, return the OID of the default partition, if
 * one exists; else, return InvalidOid.
 */
Oid
get_default_oid_from_partdesc(PartitionDesc partdesc)
{
    if (partdesc && partdesc->boundinfo &&
        partition_bound_has_default(partdesc->boundinfo))
        return partdesc->oids[partdesc->boundinfo->default_index];

    return InvalidOid;
}