createas.c

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/*-------------------------------------------------------------------------
 *
 * createas.c
 *    Execution of CREATE TABLE ... AS, a/k/a SELECT INTO.
 *    Since CREATE MATERIALIZED VIEW shares syntax and most behaviors,
 *    we implement that here, too.
 *
 * We implement this by diverting the query's normal output to a
 * specialized DestReceiver type.
 *
 * Formerly, CTAS was implemented as a variant of SELECT, which led
 * to assorted legacy behaviors that we still try to preserve, notably that
 * we must return a tuples-processed count in the QueryCompletion.  (We no
 * longer do that for CTAS ... WITH NO DATA, however.)
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/commands/createas.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "access/heapam.h"
#include "access/reloptions.h"
#include "access/tableam.h"
#include "access/xact.h"
#include "catalog/namespace.h"
#include "catalog/toasting.h"
#include "commands/createas.h"
#include "commands/matview.h"
#include "commands/prepare.h"
#include "commands/tablecmds.h"
#include "commands/view.h"
#include "executor/execdesc.h"
#include "executor/executor.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "nodes/queryjumble.h"
#include "parser/analyze.h"
#include "rewrite/rewriteHandler.h"
#include "tcop/tcopprot.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/rls.h"
#include "utils/snapmgr.h"
 
typedef struct
{
    DestReceiver pub;           /* publicly-known function pointers */
    IntoClause *into;           /* target relation specification */
    /* These fields are filled by intorel_startup: */
    Relation    rel;            /* relation to write to */
    ObjectAddress reladdr;      /* address of rel, for ExecCreateTableAs */
    CommandId   output_cid;     /* cmin to insert in output tuples */
    int         ti_options;     /* table_tuple_insert performance options */
    BulkInsertState bistate;    /* bulk insert state */
} DR_intorel;
 
/* utility functions for CTAS definition creation */
static ObjectAddress create_ctas_internal(List *attrList, IntoClause *into);
static ObjectAddress create_ctas_nodata(List *tlist, IntoClause *into);
 
/* DestReceiver routines for collecting data */
static void intorel_startup(DestReceiver *self, int operation, TupleDesc typeinfo);
static bool intorel_receive(TupleTableSlot *slot, DestReceiver *self);
static void intorel_shutdown(DestReceiver *self);
static void intorel_destroy(DestReceiver *self);
 
 
/*
 * create_ctas_internal
 *
 * Internal utility used for the creation of the definition of a relation
 * created via CREATE TABLE AS or a materialized view.  Caller needs to
 * provide a list of attributes (ColumnDef nodes).
 */
static ObjectAddress
create_ctas_internal(List *attrList, IntoClause *into)
{
    CreateStmt *create = makeNode(CreateStmt);
    bool        is_matview;
    char        relkind;
    Datum       toast_options;
    const char *const validnsps[] = HEAP_RELOPT_NAMESPACES;
    ObjectAddress intoRelationAddr;
 
    /* This code supports both CREATE TABLE AS and CREATE MATERIALIZED VIEW */
    is_matview = (into->viewQuery != NULL);
    relkind = is_matview ? RELKIND_MATVIEW : RELKIND_RELATION;
 
    /*
     * Create the target relation by faking up a CREATE TABLE parsetree and
     * passing it to DefineRelation.
     */
    create->relation = into->rel;
    create->tableElts = attrList;
    create->inhRelations = NIL;
    create->ofTypename = NULL;
    create->constraints = NIL;
    create->options = into->options;
    create->oncommit = into->onCommit;
    create->tablespacename = into->tableSpaceName;
    create->if_not_exists = false;
    create->accessMethod = into->accessMethod;
 
    /*
     * Create the relation.  (This will error out if there's an existing view,
     * so we don't need more code to complain if "replace" is false.)
     */
    intoRelationAddr = DefineRelation(create, relkind, InvalidOid, NULL, NULL);
 
    /*
     * If necessary, create a TOAST table for the target table.  Note that
     * NewRelationCreateToastTable ends with CommandCounterIncrement(), so
     * that the TOAST table will be visible for insertion.
     */
    CommandCounterIncrement();
 
    /* parse and validate reloptions for the toast table */
    toast_options = transformRelOptions((Datum) 0,
                                        create->options,
                                        "toast",
                                        validnsps,
                                        true, false);
 
    (void) heap_reloptions(RELKIND_TOASTVALUE, toast_options, true);
 
    NewRelationCreateToastTable(intoRelationAddr.objectId, toast_options);
 
    /* Create the "view" part of a materialized view. */
    if (is_matview)
    {
        /* StoreViewQuery scribbles on tree, so make a copy */
        Query      *query = copyObject(into->viewQuery);
 
        StoreViewQuery(intoRelationAddr.objectId, query, false);
        CommandCounterIncrement();
    }
 
    return intoRelationAddr;
}
 
 
/*
 * create_ctas_nodata
 *
 * Create CTAS or materialized view when WITH NO DATA is used, starting from
 * the targetlist of the SELECT or view definition.
 */
static ObjectAddress
create_ctas_nodata(List *tlist, IntoClause *into)
{
    List       *attrList;
    ListCell   *t,
               *lc;
 
    /*
     * Build list of ColumnDefs from non-junk elements of the tlist.  If a
     * column name list was specified in CREATE TABLE AS, override the column
     * names in the query.  (Too few column names are OK, too many are not.)
     */
    attrList = NIL;
    lc = list_head(into->colNames);
    foreach(t, tlist)
    {
        TargetEntry *tle = (TargetEntry *) lfirst(t);
 
        if (!tle->resjunk)
        {
            ColumnDef  *col;
            char       *colname;
 
            if (lc)
            {
                colname = strVal(lfirst(lc));
                lc = lnext(into->colNames, lc);
            }
            else
                colname = tle->resname;
 
            col = makeColumnDef(colname,
                                exprType((Node *) tle->expr),
                                exprTypmod((Node *) tle->expr),
                                exprCollation((Node *) tle->expr));
 
            /*
             * It's possible that the column is of a collatable type but the
             * collation could not be resolved, so double-check.  (We must
             * check this here because DefineRelation would adopt the type's
             * default collation rather than complaining.)
             */
            if (!OidIsValid(col->collOid) &&
                type_is_collatable(col->typeName->typeOid))
                ereport(ERROR,
                        (errcode(ERRCODE_INDETERMINATE_COLLATION),
                         errmsg("no collation was derived for column \"%s\" with collatable type %s",
                                col->colname,
                                format_type_be(col->typeName->typeOid)),
                         errhint("Use the COLLATE clause to set the collation explicitly.")));
 
            attrList = lappend(attrList, col);
        }
    }
 
    if (lc != NULL)
        ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                 errmsg("too many column names were specified")));
 
    /* Create the relation definition using the ColumnDef list */
    return create_ctas_internal(attrList, into);
}
 
 
/*
 * ExecCreateTableAs -- execute a CREATE TABLE AS command
 */
ObjectAddress
ExecCreateTableAs(ParseState *pstate, CreateTableAsStmt *stmt,
                  ParamListInfo params, QueryEnvironment *queryEnv,
                  QueryCompletion *qc)
{
    Query      *query = castNode(Query, stmt->query);
    IntoClause *into = stmt->into;
    JumbleState *jstate = NULL;
    bool        is_matview = (into->viewQuery != NULL);
    bool        do_refresh = false;
    DestReceiver *dest;
    ObjectAddress address;
 
    /* Check if the relation exists or not */
    if (CreateTableAsRelExists(stmt))
        return InvalidObjectAddress;
 
    /*
     * Create the tuple receiver object and insert info it will need
     */
    dest = CreateIntoRelDestReceiver(into);
 
    /* Query contained by CTAS needs to be jumbled if requested */
    if (IsQueryIdEnabled())
        jstate = JumbleQuery(query);
 
    if (post_parse_analyze_hook)
        (*post_parse_analyze_hook) (pstate, query, jstate);
 
    /*
     * The contained Query could be a SELECT, or an EXECUTE utility command.
     * If the latter, we just pass it off to ExecuteQuery.
     */
    if (query->commandType == CMD_UTILITY &&
        IsA(query->utilityStmt, ExecuteStmt))
    {
        ExecuteStmt *estmt = castNode(ExecuteStmt, query->utilityStmt);
 
        Assert(!is_matview);    /* excluded by syntax */
        ExecuteQuery(pstate, estmt, into, params, dest, qc);
 
        /* get object address that intorel_startup saved for us */
        address = ((DR_intorel *) dest)->reladdr;
 
        return address;
    }
    Assert(query->commandType == CMD_SELECT);
 
    /*
     * For materialized views, always skip data during table creation, and use
     * REFRESH instead (see below).
     */
    if (is_matview)
    {
        do_refresh = !into->skipData;
        into->skipData = true;
    }
 
    if (into->skipData)
    {
        /*
         * If WITH NO DATA was specified, do not go through the rewriter,
         * planner and executor.  Just define the relation using a code path
         * similar to CREATE VIEW.  This avoids dump/restore problems stemming
         * from running the planner before all dependencies are set up.
         */
        address = create_ctas_nodata(query->targetList, into);
 
        /*
         * For materialized views, reuse the REFRESH logic, which locks down
         * security-restricted operations and restricts the search_path.  This
         * reduces the chance that a subsequent refresh will fail.
         */
        if (do_refresh)
            RefreshMatViewByOid(address.objectId, true, false, false,
                                pstate->p_sourcetext, qc);
 
    }
    else
    {
        List       *rewritten;
        PlannedStmt *plan;
        QueryDesc  *queryDesc;
 
        Assert(!is_matview);
 
        /*
         * Parse analysis was done already, but we still have to run the rule
         * rewriter.  We do not do AcquireRewriteLocks: we assume the query
         * either came straight from the parser, or suitable locks were
         * acquired by plancache.c.
         */
        rewritten = QueryRewrite(query);
 
        /* SELECT should never rewrite to more or less than one SELECT query */
        if (list_length(rewritten) != 1)
            elog(ERROR, "unexpected rewrite result for CREATE TABLE AS SELECT");
        query = linitial_node(Query, rewritten);
        Assert(query->commandType == CMD_SELECT);
 
        /* plan the query */
        plan = pg_plan_query(query, pstate->p_sourcetext,
                             CURSOR_OPT_PARALLEL_OK, params);
 
        /*
         * Use a snapshot with an updated command ID to ensure this query sees
         * results of any previously executed queries.  (This could only
         * matter if the planner executed an allegedly-stable function that
         * changed the database contents, but let's do it anyway to be
         * parallel to the EXPLAIN code path.)
         */
        PushCopiedSnapshot(GetActiveSnapshot());
        UpdateActiveSnapshotCommandId();
 
        /* Create a QueryDesc, redirecting output to our tuple receiver */
        queryDesc = CreateQueryDesc(plan, NULL, pstate->p_sourcetext,
                                    GetActiveSnapshot(), InvalidSnapshot,
                                    dest, params, queryEnv, 0);
 
        /* call ExecutorStart to prepare the plan for execution */
        if (!ExecutorStart(queryDesc, GetIntoRelEFlags(into)))
            elog(ERROR, "ExecutorStart() failed unexpectedly");
 
        /* run the plan to completion */
        ExecutorRun(queryDesc, ForwardScanDirection, 0);
 
        /* save the rowcount if we're given a qc to fill */
        if (qc)
            SetQueryCompletion(qc, CMDTAG_SELECT, queryDesc->estate->es_processed);
 
        /* get object address that intorel_startup saved for us */
        address = ((DR_intorel *) dest)->reladdr;
 
        /* and clean up */
        ExecutorFinish(queryDesc);
        ExecutorEnd(queryDesc);
 
        FreeQueryDesc(queryDesc);
 
        PopActiveSnapshot();
    }
 
    return address;
}
 
/*
 * GetIntoRelEFlags --- compute executor flags needed for CREATE TABLE AS
 *
 * This is exported because EXPLAIN and PREPARE need it too.  (Note: those
 * callers still need to deal explicitly with the skipData flag; since they
 * use different methods for suppressing execution, it doesn't seem worth
 * trying to encapsulate that part.)
 */
int
GetIntoRelEFlags(IntoClause *intoClause)
{
    int         flags = 0;
 
    if (intoClause->skipData)
        flags |= EXEC_FLAG_WITH_NO_DATA;
 
    return flags;
}
 
/*
 * CreateTableAsRelExists --- check existence of relation for CreateTableAsStmt
 *
 * Utility wrapper checking if the relation pending for creation in this
 * CreateTableAsStmt query already exists or not.  Returns true if the
 * relation exists, otherwise false.
 */
bool
CreateTableAsRelExists(CreateTableAsStmt *ctas)
{
    Oid         nspid;
    Oid         oldrelid;
    ObjectAddress address;
    IntoClause *into = ctas->into;
 
    nspid = RangeVarGetCreationNamespace(into->rel);
 
    oldrelid = get_relname_relid(into->rel->relname, nspid);
    if (OidIsValid(oldrelid))
    {
        if (!ctas->if_not_exists)
            ereport(ERROR,
                    (errcode(ERRCODE_DUPLICATE_TABLE),
                     errmsg("relation \"%s\" already exists",
                            into->rel->relname)));
 
        /*
         * The relation exists and IF NOT EXISTS has been specified.
         *
         * If we are in an extension script, insist that the pre-existing
         * object be a member of the extension, to avoid security risks.
         */
        ObjectAddressSet(address, RelationRelationId, oldrelid);
        checkMembershipInCurrentExtension(&address);
 
        /* OK to skip */
        ereport(NOTICE,
                (errcode(ERRCODE_DUPLICATE_TABLE),
                 errmsg("relation \"%s\" already exists, skipping",
                        into->rel->relname)));
        return true;
    }
 
    /* Relation does not exist, it can be created */
    return false;
}
 
/*
 * CreateIntoRelDestReceiver -- create a suitable DestReceiver object
 *
 * intoClause will be NULL if called from CreateDestReceiver(), in which
 * case it has to be provided later.  However, it is convenient to allow
 * self->into to be filled in immediately for other callers.
 */
DestReceiver *
CreateIntoRelDestReceiver(IntoClause *intoClause)
{
    DR_intorel *self = (DR_intorel *) palloc0(sizeof(DR_intorel));
 
    self->pub.receiveSlot = intorel_receive;
    self->pub.rStartup = intorel_startup;
    self->pub.rShutdown = intorel_shutdown;
    self->pub.rDestroy = intorel_destroy;
    self->pub.mydest = DestIntoRel;
    self->into = intoClause;
    /* other private fields will be set during intorel_startup */
 
    return (DestReceiver *) self;
}
 
/*
 * intorel_startup --- executor startup
 */
static void
intorel_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
{
    DR_intorel *myState = (DR_intorel *) self;
    IntoClause *into = myState->into;
    bool        is_matview;
    List       *attrList;
    ObjectAddress intoRelationAddr;
    Relation    intoRelationDesc;
    ListCell   *lc;
    int         attnum;
 
    Assert(into != NULL);       /* else somebody forgot to set it */
 
    /* This code supports both CREATE TABLE AS and CREATE MATERIALIZED VIEW */
    is_matview = (into->viewQuery != NULL);
 
    /*
     * Build column definitions using "pre-cooked" type and collation info. If
     * a column name list was specified in CREATE TABLE AS, override the
     * column names derived from the query.  (Too few column names are OK, too
     * many are not.)
     */
    attrList = NIL;
    lc = list_head(into->colNames);
    for (attnum = 0; attnum < typeinfo->natts; attnum++)
    {
        Form_pg_attribute attribute = TupleDescAttr(typeinfo, attnum);
        ColumnDef  *col;
        char       *colname;
 
        if (lc)
        {
            colname = strVal(lfirst(lc));
            lc = lnext(into->colNames, lc);
        }
        else
            colname = NameStr(attribute->attname);
 
        col = makeColumnDef(colname,
                            attribute->atttypid,
                            attribute->atttypmod,
                            attribute->attcollation);
 
        /*
         * It's possible that the column is of a collatable type but the
         * collation could not be resolved, so double-check.  (We must check
         * this here because DefineRelation would adopt the type's default
         * collation rather than complaining.)
         */
        if (!OidIsValid(col->collOid) &&
            type_is_collatable(col->typeName->typeOid))
            ereport(ERROR,
                    (errcode(ERRCODE_INDETERMINATE_COLLATION),
                     errmsg("no collation was derived for column \"%s\" with collatable type %s",
                            col->colname,
                            format_type_be(col->typeName->typeOid)),
                     errhint("Use the COLLATE clause to set the collation explicitly.")));
 
        attrList = lappend(attrList, col);
    }
 
    if (lc != NULL)
        ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                 errmsg("too many column names were specified")));
 
    /*
     * Actually create the target table
     */
    intoRelationAddr = create_ctas_internal(attrList, into);
 
    /*
     * Finally we can open the target table
     */
    intoRelationDesc = table_open(intoRelationAddr.objectId, AccessExclusiveLock);
 
    /*
     * Make sure the constructed table does not have RLS enabled.
     *
     * check_enable_rls() will ereport(ERROR) itself if the user has requested
     * something invalid, and otherwise will return RLS_ENABLED if RLS should
     * be enabled here.  We don't actually support that currently, so throw
     * our own ereport(ERROR) if that happens.
     */
    if (check_enable_rls(intoRelationAddr.objectId, InvalidOid, false) == RLS_ENABLED)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("policies not yet implemented for this command")));
 
    /*
     * Tentatively mark the target as populated, if it's a matview and we're
     * going to fill it; otherwise, no change needed.
     */
    if (is_matview && !into->skipData)
        SetMatViewPopulatedState(intoRelationDesc, true);
 
    /*
     * Fill private fields of myState for use by later routines
     */
    myState->rel = intoRelationDesc;
    myState->reladdr = intoRelationAddr;
    myState->output_cid = GetCurrentCommandId(true);
    myState->ti_options = TABLE_INSERT_SKIP_FSM;
 
    /*
     * If WITH NO DATA is specified, there is no need to set up the state for
     * bulk inserts as there are no tuples to insert.
     */
    if (!into->skipData)
        myState->bistate = GetBulkInsertState();
    else
        myState->bistate = NULL;
 
    /*
     * Valid smgr_targblock implies something already wrote to the relation.
     * This may be harmless, but this function hasn't planned for it.
     */
    Assert(RelationGetTargetBlock(intoRelationDesc) == InvalidBlockNumber);
}
 
/*
 * intorel_receive --- receive one tuple
 */
static bool
intorel_receive(TupleTableSlot *slot, DestReceiver *self)
{
    DR_intorel *myState = (DR_intorel *) self;
 
    /* Nothing to insert if WITH NO DATA is specified. */
    if (!myState->into->skipData)
    {
        /*
         * Note that the input slot might not be of the type of the target
         * relation. That's supported by table_tuple_insert(), but slightly
         * less efficient than inserting with the right slot - but the
         * alternative would be to copy into a slot of the right type, which
         * would not be cheap either. This also doesn't allow accessing per-AM
         * data (say a tuple's xmin), but since we don't do that here...
         */
        table_tuple_insert(myState->rel,
                           slot,
                           myState->output_cid,
                           myState->ti_options,
                           myState->bistate);
    }
 
    /* We know this is a newly created relation, so there are no indexes */
 
    return true;
}
 
/*
 * intorel_shutdown --- executor end
 */
static void
intorel_shutdown(DestReceiver *self)
{
    DR_intorel *myState = (DR_intorel *) self;
    IntoClause *into = myState->into;
 
    if (!into->skipData)
    {
        FreeBulkInsertState(myState->bistate);
        table_finish_bulk_insert(myState->rel, myState->ti_options);
    }
 
    /* close rel, but keep lock until commit */
    table_close(myState->rel, NoLock);
    myState->rel = NULL;
}
 
/*
 * intorel_destroy --- release DestReceiver object
 */
static void
intorel_destroy(DestReceiver *self)
{
    pfree(self);
}