indexing.c

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/*-------------------------------------------------------------------------
 *
 * indexing.c
 *    This file contains routines to support indexes defined on system
 *    catalogs.
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/catalog/indexing.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "access/htup_details.h"
#include "access/xact.h"
#include "catalog/index.h"
#include "catalog/indexing.h"
#include "executor/executor.h"
#include "utils/rel.h"


/*
 * CatalogOpenIndexes - open the indexes on a system catalog.
 *
 * When inserting or updating tuples in a system catalog, call this
 * to prepare to update the indexes for the catalog.
 *
 * In the current implementation, we share code for opening/closing the
 * indexes with execUtils.c.  But we do not use ExecInsertIndexTuples,
 * because we don't want to create an EState.  This implies that we
 * do not support partial or expressional indexes on system catalogs,
 * nor can we support generalized exclusion constraints.
 * This could be fixed with localized changes here if we wanted to pay
 * the extra overhead of building an EState.
 */
CatalogIndexState
CatalogOpenIndexes(Relation heapRel)
{
    ResultRelInfo *resultRelInfo;

    resultRelInfo = makeNode(ResultRelInfo);
    resultRelInfo->ri_RangeTableIndex = 0;  /* dummy */
    resultRelInfo->ri_RelationDesc = heapRel;
    resultRelInfo->ri_TrigDesc = NULL;  /* we don't fire triggers */

    ExecOpenIndices(resultRelInfo, false);

    return resultRelInfo;
}

/*
 * CatalogCloseIndexes - clean up resources allocated by CatalogOpenIndexes
 */
void
CatalogCloseIndexes(CatalogIndexState indstate)
{
    ExecCloseIndices(indstate);
    pfree(indstate);
}

/*
 * CatalogIndexInsert - insert index entries for one catalog tuple
 *
 * This should be called for each inserted or updated catalog tuple.
 *
 * This is effectively a cut-down version of ExecInsertIndexTuples.
 */
static void
CatalogIndexInsert(CatalogIndexState indstate, HeapTuple heapTuple)
{
    int         i;
    int         numIndexes;
    RelationPtr relationDescs;
    Relation    heapRelation;
    TupleTableSlot *slot;
    IndexInfo **indexInfoArray;
    Datum       values[INDEX_MAX_KEYS];
    bool        isnull[INDEX_MAX_KEYS];

    /*
     * HOT update does not require index inserts. But with asserts enabled we
     * want to check that it'd be legal to currently insert into the
     * table/index.
     */
#ifndef USE_ASSERT_CHECKING
    if (HeapTupleIsHeapOnly(heapTuple))
        return;
#endif

    /*
     * Get information from the state structure.  Fall out if nothing to do.
     */
    numIndexes = indstate->ri_NumIndices;
    if (numIndexes == 0)
        return;
    relationDescs = indstate->ri_IndexRelationDescs;
    indexInfoArray = indstate->ri_IndexRelationInfo;
    heapRelation = indstate->ri_RelationDesc;

    /* Need a slot to hold the tuple being examined */
    slot = MakeSingleTupleTableSlot(RelationGetDescr(heapRelation),
                                    &TTSOpsHeapTuple);
    ExecStoreHeapTuple(heapTuple, slot, false);

    /*
     * for each index, form and insert the index tuple
     */
    for (i = 0; i < numIndexes; i++)
    {
        IndexInfo  *indexInfo;
        Relation    index;

        indexInfo = indexInfoArray[i];
        index = relationDescs[i];

        /* If the index is marked as read-only, ignore it */
        if (!indexInfo->ii_ReadyForInserts)
            continue;

        /*
         * Expressional and partial indexes on system catalogs are not
         * supported, nor exclusion constraints, nor deferred uniqueness
         */
        Assert(indexInfo->ii_Expressions == NIL);
        Assert(indexInfo->ii_Predicate == NIL);
        Assert(indexInfo->ii_ExclusionOps == NULL);
        Assert(index->rd_index->indimmediate);
        Assert(indexInfo->ii_NumIndexKeyAttrs != 0);

        /* see earlier check above */
#ifdef USE_ASSERT_CHECKING
        if (HeapTupleIsHeapOnly(heapTuple))
        {
            Assert(!ReindexIsProcessingIndex(RelationGetRelid(index)));
            continue;
        }
#endif                          /* USE_ASSERT_CHECKING */

        /*
         * FormIndexDatum fills in its values and isnull parameters with the
         * appropriate values for the column(s) of the index.
         */
        FormIndexDatum(indexInfo,
                       slot,
                       NULL,    /* no expression eval to do */
                       values,
                       isnull);

        /*
         * The index AM does the rest.
         */
        index_insert(index,     /* index relation */
                     values,    /* array of index Datums */
                     isnull,    /* is-null flags */
                     &(heapTuple->t_self),  /* tid of heap tuple */
                     heapRelation,
                     index->rd_index->indisunique ?
                     UNIQUE_CHECK_YES : UNIQUE_CHECK_NO,
                     false,
                     indexInfo);
    }

    ExecDropSingleTupleTableSlot(slot);
}

/*
 * Subroutine to verify that catalog constraints are honored.
 *
 * Tuples inserted via CatalogTupleInsert/CatalogTupleUpdate are generally
 * "hand made", so that it's possible that they fail to satisfy constraints
 * that would be checked if they were being inserted by the executor.  That's
 * a coding error, so we only bother to check for it in assert-enabled builds.
 */
#ifdef USE_ASSERT_CHECKING

static void
CatalogTupleCheckConstraints(Relation heapRel, HeapTuple tup)
{
    /*
     * Currently, the only constraints implemented for system catalogs are
     * attnotnull constraints.
     */
    if (HeapTupleHasNulls(tup))
    {
        TupleDesc   tupdesc = RelationGetDescr(heapRel);
        bits8      *bp = tup->t_data->t_bits;

        for (int attnum = 0; attnum < tupdesc->natts; attnum++)
        {
            Form_pg_attribute thisatt = TupleDescAttr(tupdesc, attnum);

            Assert(!(thisatt->attnotnull && att_isnull(attnum, bp)));
        }
    }
}

#else                           /* !USE_ASSERT_CHECKING */

#define CatalogTupleCheckConstraints(heapRel, tup)  ((void) 0)

#endif                          /* USE_ASSERT_CHECKING */

/*
 * CatalogTupleInsert - do heap and indexing work for a new catalog tuple
 *
 * Insert the tuple data in "tup" into the specified catalog relation.
 * The Oid of the inserted tuple is returned.
 *
 * This is a convenience routine for the common case of inserting a single
 * tuple in a system catalog; it inserts a new heap tuple, keeping indexes
 * current.  Avoid using it for multiple tuples, since opening the indexes
 * and building the index info structures is moderately expensive.
 * (Use CatalogTupleInsertWithInfo in such cases.)
 */
void
CatalogTupleInsert(Relation heapRel, HeapTuple tup)
{
    CatalogIndexState indstate;

    CatalogTupleCheckConstraints(heapRel, tup);

    indstate = CatalogOpenIndexes(heapRel);

    simple_heap_insert(heapRel, tup);

    CatalogIndexInsert(indstate, tup);
    CatalogCloseIndexes(indstate);
}

/*
 * CatalogTupleInsertWithInfo - as above, but with caller-supplied index info
 *
 * This should be used when it's important to amortize CatalogOpenIndexes/
 * CatalogCloseIndexes work across multiple insertions.  At some point we
 * might cache the CatalogIndexState data somewhere (perhaps in the relcache)
 * so that callers needn't trouble over this ... but we don't do so today.
 */
void
CatalogTupleInsertWithInfo(Relation heapRel, HeapTuple tup,
                           CatalogIndexState indstate)
{
    CatalogTupleCheckConstraints(heapRel, tup);

    simple_heap_insert(heapRel, tup);

    CatalogIndexInsert(indstate, tup);
}

/*
 * CatalogTuplesMultiInsertWithInfo - as above, but for multiple tuples
 *
 * Insert multiple tuples into the given catalog relation at once, with an
 * amortized cost of CatalogOpenIndexes.
 */
void
CatalogTuplesMultiInsertWithInfo(Relation heapRel, TupleTableSlot **slot,
                                 int ntuples, CatalogIndexState indstate)
{
    /* Nothing to do */
    if (ntuples <= 0)
        return;

    heap_multi_insert(heapRel, slot, ntuples,
                      GetCurrentCommandId(true), 0, NULL);

    /*
     * There is no equivalent to heap_multi_insert for the catalog indexes, so
     * we must loop over and insert individually.
     */
    for (int i = 0; i < ntuples; i++)
    {
        bool        should_free;
        HeapTuple   tuple;

        tuple = ExecFetchSlotHeapTuple(slot[i], true, &should_free);
        tuple->t_tableOid = slot[i]->tts_tableOid;
        CatalogIndexInsert(indstate, tuple);

        if (should_free)
            heap_freetuple(tuple);
    }
}

/*
 * CatalogTupleUpdate - do heap and indexing work for updating a catalog tuple
 *
 * Update the tuple identified by "otid", replacing it with the data in "tup".
 *
 * This is a convenience routine for the common case of updating a single
 * tuple in a system catalog; it updates one heap tuple, keeping indexes
 * current.  Avoid using it for multiple tuples, since opening the indexes
 * and building the index info structures is moderately expensive.
 * (Use CatalogTupleUpdateWithInfo in such cases.)
 */
void
CatalogTupleUpdate(Relation heapRel, ItemPointer otid, HeapTuple tup)
{
    CatalogIndexState indstate;

    CatalogTupleCheckConstraints(heapRel, tup);

    indstate = CatalogOpenIndexes(heapRel);

    simple_heap_update(heapRel, otid, tup);

    CatalogIndexInsert(indstate, tup);
    CatalogCloseIndexes(indstate);
}

/*
 * CatalogTupleUpdateWithInfo - as above, but with caller-supplied index info
 *
 * This should be used when it's important to amortize CatalogOpenIndexes/
 * CatalogCloseIndexes work across multiple updates.  At some point we
 * might cache the CatalogIndexState data somewhere (perhaps in the relcache)
 * so that callers needn't trouble over this ... but we don't do so today.
 */
void
CatalogTupleUpdateWithInfo(Relation heapRel, ItemPointer otid, HeapTuple tup,
                           CatalogIndexState indstate)
{
    CatalogTupleCheckConstraints(heapRel, tup);

    simple_heap_update(heapRel, otid, tup);

    CatalogIndexInsert(indstate, tup);
}

/*
 * CatalogTupleDelete - do heap and indexing work for deleting a catalog tuple
 *
 * Delete the tuple identified by "tid" in the specified catalog.
 *
 * With Postgres heaps, there is no index work to do at deletion time;
 * cleanup will be done later by VACUUM.  However, callers of this function
 * shouldn't have to know that; we'd like a uniform abstraction for all
 * catalog tuple changes.  Hence, provide this currently-trivial wrapper.
 *
 * The abstraction is a bit leaky in that we don't provide an optimized
 * CatalogTupleDeleteWithInfo version, because there is currently nothing to
 * optimize.  If we ever need that, rather than touching a lot of call sites,
 * it might be better to do something about caching CatalogIndexState.
 */
void
CatalogTupleDelete(Relation heapRel, ItemPointer tid)
{
    simple_heap_delete(heapRel, tid);
}