toasting.c

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * toasting.c
 *    This file contains routines to support creation of toast tables
 *
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/catalog/toasting.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/heapam.h"
#include "access/toast_compression.h"
#include "access/xact.h"
#include "catalog/binary_upgrade.h"
#include "catalog/catalog.h"
#include "catalog/dependency.h"
#include "catalog/heap.h"
#include "catalog/index.h"
#include "catalog/namespace.h"
#include "catalog/pg_am.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_type.h"
#include "catalog/toasting.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "storage/lock.h"
#include "utils/builtins.h"
#include "utils/rel.h"
#include "utils/syscache.h"

static void CheckAndCreateToastTable(Oid relOid, Datum reloptions,
                                     LOCKMODE lockmode, bool check);
static bool create_toast_table(Relation rel, Oid toastOid, Oid toastIndexOid,
                               Datum reloptions, LOCKMODE lockmode, bool check);
static bool needs_toast_table(Relation rel);


/*
 * CreateToastTable variants
 *      If the table needs a toast table, and doesn't already have one,
 *      then create a toast table for it.
 *
 * reloptions for the toast table can be passed, too.  Pass (Datum) 0
 * for default reloptions.
 *
 * We expect the caller to have verified that the relation is a table and have
 * already done any necessary permission checks.  Callers expect this function
 * to end with CommandCounterIncrement if it makes any changes.
 */
void
AlterTableCreateToastTable(Oid relOid, Datum reloptions, LOCKMODE lockmode)
{
    CheckAndCreateToastTable(relOid, reloptions, lockmode, true);
}

void
NewHeapCreateToastTable(Oid relOid, Datum reloptions, LOCKMODE lockmode)
{
    CheckAndCreateToastTable(relOid, reloptions, lockmode, false);
}

void
NewRelationCreateToastTable(Oid relOid, Datum reloptions)
{
    CheckAndCreateToastTable(relOid, reloptions, AccessExclusiveLock, false);
}

static void
CheckAndCreateToastTable(Oid relOid, Datum reloptions, LOCKMODE lockmode, bool check)
{
    Relation    rel;

    rel = table_open(relOid, lockmode);

    /* create_toast_table does all the work */
    (void) create_toast_table(rel, InvalidOid, InvalidOid, reloptions, lockmode, check);

    table_close(rel, NoLock);
}

/*
 * Create a toast table during bootstrap
 *
 * Here we need to prespecify the OIDs of the toast table and its index
 */
void
BootstrapToastTable(char *relName, Oid toastOid, Oid toastIndexOid)
{
    Relation    rel;

    rel = table_openrv(makeRangeVar(NULL, relName, -1), AccessExclusiveLock);

    if (rel->rd_rel->relkind != RELKIND_RELATION &&
        rel->rd_rel->relkind != RELKIND_MATVIEW)
        elog(ERROR, "\"%s\" is not a table or materialized view",
             relName);

    /* create_toast_table does all the work */
    if (!create_toast_table(rel, toastOid, toastIndexOid, (Datum) 0,
                            AccessExclusiveLock, false))
        elog(ERROR, "\"%s\" does not require a toast table",
             relName);

    table_close(rel, NoLock);
}


/*
 * create_toast_table --- internal workhorse
 *
 * rel is already opened and locked
 * toastOid and toastIndexOid are normally InvalidOid, but during
 * bootstrap they can be nonzero to specify hand-assigned OIDs
 */
static bool
create_toast_table(Relation rel, Oid toastOid, Oid toastIndexOid,
                   Datum reloptions, LOCKMODE lockmode, bool check)
{
    Oid         relOid = RelationGetRelid(rel);
    HeapTuple   reltup;
    TupleDesc   tupdesc;
    bool        shared_relation;
    bool        mapped_relation;
    Relation    toast_rel;
    Relation    class_rel;
    Oid         toast_relid;
    Oid         namespaceid;
    char        toast_relname[NAMEDATALEN];
    char        toast_idxname[NAMEDATALEN];
    IndexInfo  *indexInfo;
    Oid         collationObjectId[2];
    Oid         classObjectId[2];
    int16       coloptions[2];
    ObjectAddress baseobject,
                toastobject;

    /*
     * Is it already toasted?
     */
    if (rel->rd_rel->reltoastrelid != InvalidOid)
        return false;

    /*
     * Check to see whether the table actually needs a TOAST table.
     */
    if (!IsBinaryUpgrade)
    {
        /* Normal mode, normal check */
        if (!needs_toast_table(rel))
            return false;
    }
    else
    {
        /*
         * In binary-upgrade mode, create a TOAST table if and only if
         * pg_upgrade told us to (ie, a TOAST table OID has been provided).
         *
         * This indicates that the old cluster had a TOAST table for the
         * current table.  We must create a TOAST table to receive the old
         * TOAST file, even if the table seems not to need one.
         *
         * Contrariwise, if the old cluster did not have a TOAST table, we
         * should be able to get along without one even if the new version's
         * needs_toast_table rules suggest we should have one.  There is a lot
         * of daylight between where we will create a TOAST table and where
         * one is really necessary to avoid failures, so small cross-version
         * differences in the when-to-create heuristic shouldn't be a problem.
         * If we tried to create a TOAST table anyway, we would have the
         * problem that it might take up an OID that will conflict with some
         * old-cluster table we haven't seen yet.
         */
        if (!OidIsValid(binary_upgrade_next_toast_pg_class_oid))
            return false;
    }

    /*
     * If requested check lockmode is sufficient. This is a cross check in
     * case of errors or conflicting decisions in earlier code.
     */
    if (check && lockmode != AccessExclusiveLock)
        elog(ERROR, "AccessExclusiveLock required to add toast table.");

    /*
     * Create the toast table and its index
     */
    snprintf(toast_relname, sizeof(toast_relname),
             "pg_toast_%u", relOid);
    snprintf(toast_idxname, sizeof(toast_idxname),
             "pg_toast_%u_index", relOid);

    /* this is pretty painful...  need a tuple descriptor */
    tupdesc = CreateTemplateTupleDesc(3);
    TupleDescInitEntry(tupdesc, (AttrNumber) 1,
                       "chunk_id",
                       OIDOID,
                       -1, 0);
    TupleDescInitEntry(tupdesc, (AttrNumber) 2,
                       "chunk_seq",
                       INT4OID,
                       -1, 0);
    TupleDescInitEntry(tupdesc, (AttrNumber) 3,
                       "chunk_data",
                       BYTEAOID,
                       -1, 0);

    /*
     * Ensure that the toast table doesn't itself get toasted, or we'll be
     * toast :-(.  This is essential for chunk_data because type bytea is
     * toastable; hit the other two just to be sure.
     */
    TupleDescAttr(tupdesc, 0)->attstorage = TYPSTORAGE_PLAIN;
    TupleDescAttr(tupdesc, 1)->attstorage = TYPSTORAGE_PLAIN;
    TupleDescAttr(tupdesc, 2)->attstorage = TYPSTORAGE_PLAIN;

    /* Toast field should not be compressed */
    TupleDescAttr(tupdesc, 0)->attcompression = InvalidCompressionMethod;
    TupleDescAttr(tupdesc, 1)->attcompression = InvalidCompressionMethod;
    TupleDescAttr(tupdesc, 2)->attcompression = InvalidCompressionMethod;

    /*
     * Toast tables for regular relations go in pg_toast; those for temp
     * relations go into the per-backend temp-toast-table namespace.
     */
    if (isTempOrTempToastNamespace(rel->rd_rel->relnamespace))
        namespaceid = GetTempToastNamespace();
    else
        namespaceid = PG_TOAST_NAMESPACE;

    /* Toast table is shared if and only if its parent is. */
    shared_relation = rel->rd_rel->relisshared;

    /* It's mapped if and only if its parent is, too */
    mapped_relation = RelationIsMapped(rel);

    toast_relid = heap_create_with_catalog(toast_relname,
                                           namespaceid,
                                           rel->rd_rel->reltablespace,
                                           toastOid,
                                           InvalidOid,
                                           InvalidOid,
                                           rel->rd_rel->relowner,
                                           table_relation_toast_am(rel),
                                           tupdesc,
                                           NIL,
                                           RELKIND_TOASTVALUE,
                                           rel->rd_rel->relpersistence,
                                           shared_relation,
                                           mapped_relation,
                                           ONCOMMIT_NOOP,
                                           reloptions,
                                           false,
                                           true,
                                           true,
                                           InvalidOid,
                                           NULL);
    Assert(toast_relid != InvalidOid);

    /* make the toast relation visible, else table_open will fail */
    CommandCounterIncrement();

    /* ShareLock is not really needed here, but take it anyway */
    toast_rel = table_open(toast_relid, ShareLock);

    /*
     * Create unique index on chunk_id, chunk_seq.
     *
     * NOTE: the normal TOAST access routines could actually function with a
     * single-column index on chunk_id only. However, the slice access
     * routines use both columns for faster access to an individual chunk. In
     * addition, we want it to be unique as a check against the possibility of
     * duplicate TOAST chunk OIDs. The index might also be a little more
     * efficient this way, since btree isn't all that happy with large numbers
     * of equal keys.
     */

    indexInfo = makeNode(IndexInfo);
    indexInfo->ii_NumIndexAttrs = 2;
    indexInfo->ii_NumIndexKeyAttrs = 2;
    indexInfo->ii_IndexAttrNumbers[0] = 1;
    indexInfo->ii_IndexAttrNumbers[1] = 2;
    indexInfo->ii_Expressions = NIL;
    indexInfo->ii_ExpressionsState = NIL;
    indexInfo->ii_Predicate = NIL;
    indexInfo->ii_PredicateState = NULL;
    indexInfo->ii_ExclusionOps = NULL;
    indexInfo->ii_ExclusionProcs = NULL;
    indexInfo->ii_ExclusionStrats = NULL;
    indexInfo->ii_OpclassOptions = NULL;
    indexInfo->ii_Unique = true;
    indexInfo->ii_ReadyForInserts = true;
    indexInfo->ii_Concurrent = false;
    indexInfo->ii_BrokenHotChain = false;
    indexInfo->ii_ParallelWorkers = 0;
    indexInfo->ii_Am = BTREE_AM_OID;
    indexInfo->ii_AmCache = NULL;
    indexInfo->ii_Context = CurrentMemoryContext;

    collationObjectId[0] = InvalidOid;
    collationObjectId[1] = InvalidOid;

    classObjectId[0] = OID_BTREE_OPS_OID;
    classObjectId[1] = INT4_BTREE_OPS_OID;

    coloptions[0] = 0;
    coloptions[1] = 0;

    index_create(toast_rel, toast_idxname, toastIndexOid, InvalidOid,
                 InvalidOid, InvalidOid,
                 indexInfo,
                 list_make2("chunk_id", "chunk_seq"),
                 BTREE_AM_OID,
                 rel->rd_rel->reltablespace,
                 collationObjectId, classObjectId, coloptions, (Datum) 0,
                 INDEX_CREATE_IS_PRIMARY, 0, true, true, NULL);

    table_close(toast_rel, NoLock);

    /*
     * Store the toast table's OID in the parent relation's pg_class row
     */
    class_rel = table_open(RelationRelationId, RowExclusiveLock);

    reltup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relOid));
    if (!HeapTupleIsValid(reltup))
        elog(ERROR, "cache lookup failed for relation %u", relOid);

    ((Form_pg_class) GETSTRUCT(reltup))->reltoastrelid = toast_relid;

    if (!IsBootstrapProcessingMode())
    {
        /* normal case, use a transactional update */
        CatalogTupleUpdate(class_rel, &reltup->t_self, reltup);
    }
    else
    {
        /* While bootstrapping, we cannot UPDATE, so overwrite in-place */
        heap_inplace_update(class_rel, reltup);
    }

    heap_freetuple(reltup);

    table_close(class_rel, RowExclusiveLock);

    /*
     * Register dependency from the toast table to the main, so that the toast
     * table will be deleted if the main is.  Skip this in bootstrap mode.
     */
    if (!IsBootstrapProcessingMode())
    {
        baseobject.classId = RelationRelationId;
        baseobject.objectId = relOid;
        baseobject.objectSubId = 0;
        toastobject.classId = RelationRelationId;
        toastobject.objectId = toast_relid;
        toastobject.objectSubId = 0;

        recordDependencyOn(&toastobject, &baseobject, DEPENDENCY_INTERNAL);
    }

    /*
     * Make changes visible
     */
    CommandCounterIncrement();

    return true;
}

/*
 * Check to see whether the table needs a TOAST table.
 */
static bool
needs_toast_table(Relation rel)
{
    /*
     * No need to create a TOAST table for partitioned tables.
     */
    if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
        return false;

    /*
     * We cannot allow toasting a shared relation after initdb (because
     * there's no way to mark it toasted in other databases' pg_class).
     */
    if (rel->rd_rel->relisshared && !IsBootstrapProcessingMode())
        return false;

    /*
     * Ignore attempts to create toast tables on catalog tables after initdb.
     * Which catalogs get toast tables is explicitly chosen in catalog/pg_*.h.
     * (We could get here via some ALTER TABLE command if the catalog doesn't
     * have a toast table.)
     */
    if (IsCatalogRelation(rel) && !IsBootstrapProcessingMode())
        return false;

    /* Otherwise, let the AM decide. */
    return table_relation_needs_toast_table(rel);
}