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 completionTag.
 *
 * Portions Copyright (c) 1996-2013, 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/reloptions.h"
#include "access/htup_details.h"
#include "access/sysattr.h"
#include "access/xact.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 "parser/parse_clause.h"
#include "rewrite/rewriteHandler.h"
#include "storage/smgr.h"
#include "tcop/tcopprot.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/rel.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 */
    CommandId   output_cid;     /* cmin to insert in output tuples */
    int         hi_options;     /* heap_insert performance options */
    BulkInsertState bistate;    /* bulk insert state */
} DR_intorel;

static void intorel_startup(DestReceiver *self, int operation, TupleDesc typeinfo);
static void intorel_receive(TupleTableSlot *slot, DestReceiver *self);
static void intorel_shutdown(DestReceiver *self);
static void intorel_destroy(DestReceiver *self);


/*
 * ExecCreateTableAs -- execute a CREATE TABLE AS command
 */
void
ExecCreateTableAs(CreateTableAsStmt *stmt, const char *queryString,
                  ParamListInfo params, char *completionTag)
{
    Query      *query = (Query *) stmt->query;
    IntoClause *into = stmt->into;
    DestReceiver *dest;
    List       *rewritten;
    PlannedStmt *plan;
    QueryDesc  *queryDesc;
    ScanDirection dir;

    /*
     * Create the tuple receiver object and insert info it will need
     */
    dest = CreateIntoRelDestReceiver(into);

    /*
     * The contained Query could be a SELECT, or an EXECUTE utility command.
     * If the latter, we just pass it off to ExecuteQuery.
     */
    Assert(IsA(query, Query));
    if (query->commandType == CMD_UTILITY &&
        IsA(query->utilityStmt, ExecuteStmt))
    {
        ExecuteStmt *estmt = (ExecuteStmt *) query->utilityStmt;

        ExecuteQuery(estmt, into, queryString, params, dest, completionTag);

        return;
    }
    Assert(query->commandType == CMD_SELECT);

    /*
     * 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.
     *
     * Because the rewriter and planner tend to scribble on the input, we make
     * a preliminary copy of the source querytree.  This prevents problems in
     * the case that CTAS is in a portal or plpgsql function and is executed
     * repeatedly.  (See also the same hack in EXPLAIN and PREPARE.)
     */
    rewritten = QueryRewrite((Query *) copyObject(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 = (Query *) linitial(rewritten);
    Assert(query->commandType == CMD_SELECT);

    /* plan the query */
    plan = pg_plan_query(query, 0, 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, queryString,
                                GetActiveSnapshot(), InvalidSnapshot,
                                dest, params, 0);

    /* call ExecutorStart to prepare the plan for execution */
    ExecutorStart(queryDesc, GetIntoRelEFlags(into));

    /*
     * Normally, we run the plan to completion; but if skipData is specified,
     * just do tuple receiver startup and shutdown.
     */
    if (into->skipData)
        dir = NoMovementScanDirection;
    else
        dir = ForwardScanDirection;

    /* run the plan */
    ExecutorRun(queryDesc, dir, 0L);

    /* save the rowcount if we're given a completionTag to fill */
    if (completionTag)
        snprintf(completionTag, COMPLETION_TAG_BUFSIZE,
                 "SELECT %u", queryDesc->estate->es_processed);

    /* and clean up */
    ExecutorFinish(queryDesc);
    ExecutorEnd(queryDesc);

    FreeQueryDesc(queryDesc);

    PopActiveSnapshot();
}

/*
 * 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;

    /*
     * We need to tell the executor whether it has to produce OIDs or not,
     * because it doesn't have enough information to do so itself (since we
     * can't build the target relation until after ExecutorStart).
     *
     * Disallow the OIDS option for materialized views.
     */
    if (interpretOidsOption(intoClause->options,
                            (intoClause->viewQuery == NULL)))
        flags = EXEC_FLAG_WITH_OIDS;
    else
        flags = EXEC_FLAG_WITHOUT_OIDS;

    if (intoClause->skipData)
        flags |= EXEC_FLAG_WITH_NO_DATA;

    return flags;
}

/*
 * 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;
    char        relkind;
    CreateStmt *create;
    Oid         intoRelationId;
    Relation    intoRelationDesc;
    RangeTblEntry *rte;
    Datum       toast_options;
    ListCell   *lc;
    int         attnum;
    static char *validnsps[] = HEAP_RELOPT_NAMESPACES;

    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);
    relkind = is_matview ? RELKIND_MATVIEW : RELKIND_RELATION;

    /*
     * Create the target relation by faking up a CREATE TABLE parsetree and
     * passing it to DefineRelation.
     */
    create = makeNode(CreateStmt);
    create->relation = into->rel;
    create->tableElts = NIL;    /* will fill below */
    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;

    /*
     * 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.)
     */
    lc = list_head(into->colNames);
    for (attnum = 0; attnum < typeinfo->natts; attnum++)
    {
        Form_pg_attribute attribute = typeinfo->attrs[attnum];
        ColumnDef  *col = makeNode(ColumnDef);
        TypeName   *coltype = makeNode(TypeName);

        if (lc)
        {
            col->colname = strVal(lfirst(lc));
            lc = lnext(lc);
        }
        else
            col->colname = NameStr(attribute->attname);
        col->typeName = coltype;
        col->inhcount = 0;
        col->is_local = true;
        col->is_not_null = false;
        col->is_from_type = false;
        col->storage = 0;
        col->raw_default = NULL;
        col->cooked_default = NULL;
        col->collClause = NULL;
        col->collOid = attribute->attcollation;
        col->constraints = NIL;
        col->fdwoptions = NIL;

        coltype->names = NIL;
        coltype->typeOid = attribute->atttypid;
        coltype->setof = false;
        coltype->pct_type = false;
        coltype->typmods = NIL;
        coltype->typemod = attribute->atttypmod;
        coltype->arrayBounds = NIL;
        coltype->location = -1;

        /*
         * 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(coltype->typeOid))
            ereport(ERROR,
                    (errcode(ERRCODE_INDETERMINATE_COLLATION),
                     errmsg("no collation was derived for column \"%s\" with collatable type %s",
                            col->colname, format_type_be(coltype->typeOid)),
                     errhint("Use the COLLATE clause to set the collation explicitly.")));

        create->tableElts = lappend(create->tableElts, col);
    }

    if (lc != NULL)
        ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                 errmsg("too many column names were specified")));

    /*
     * Actually create the target table
     */
    intoRelationId = DefineRelation(create, relkind, InvalidOid);

    /*
     * If necessary, create a TOAST table for the target table.  Note that
     * AlterTableCreateToastTable 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);

    AlterTableCreateToastTable(intoRelationId, toast_options);

    /* Create the "view" part of a materialized view. */
    if (is_matview)
    {
        /* StoreViewQuery scribbles on tree, so make a copy */
        Query  *query = (Query *) copyObject(into->viewQuery);

        StoreViewQuery(intoRelationId, query, false);
        CommandCounterIncrement();
    }

    /*
     * Finally we can open the target table
     */
    intoRelationDesc = heap_open(intoRelationId, AccessExclusiveLock);

    if (is_matview && !into->skipData)
        /* Make sure the heap looks good even if no rows are written. */
        SetMatViewToPopulated(intoRelationDesc);

    /*
     * Check INSERT permission on the constructed table.
     *
     * XXX: It would arguably make sense to skip this check if into->skipData
     * is true.
     */
    rte = makeNode(RangeTblEntry);
    rte->rtekind = RTE_RELATION;
    rte->relid = intoRelationId;
    rte->relkind = relkind;
    rte->requiredPerms = ACL_INSERT;

    for (attnum = 1; attnum <= intoRelationDesc->rd_att->natts; attnum++)
        rte->modifiedCols = bms_add_member(rte->modifiedCols,
                                attnum - FirstLowInvalidHeapAttributeNumber);

    ExecCheckRTPerms(list_make1(rte), true);

    /*
     * Fill private fields of myState for use by later routines
     */
    myState->rel = intoRelationDesc;
    myState->output_cid = GetCurrentCommandId(true);

    /*
     * We can skip WAL-logging the insertions, unless PITR or streaming
     * replication is in use. We can skip the FSM in any case.
     */
    myState->hi_options = HEAP_INSERT_SKIP_FSM |
        (XLogIsNeeded() ? 0 : HEAP_INSERT_SKIP_WAL);
    myState->bistate = GetBulkInsertState();

    /* Not using WAL requires smgr_targblock be initially invalid */
    Assert(RelationGetTargetBlock(intoRelationDesc) == InvalidBlockNumber);
}

/*
 * intorel_receive --- receive one tuple
 */
static void
intorel_receive(TupleTableSlot *slot, DestReceiver *self)
{
    DR_intorel *myState = (DR_intorel *) self;
    HeapTuple   tuple;

    /*
     * get the heap tuple out of the tuple table slot, making sure we have a
     * writable copy
     */
    tuple = ExecMaterializeSlot(slot);

    /*
     * force assignment of new OID (see comments in ExecInsert)
     */
    if (myState->rel->rd_rel->relhasoids)
        HeapTupleSetOid(tuple, InvalidOid);

    heap_insert(myState->rel,
                tuple,
                myState->output_cid,
                myState->hi_options,
                myState->bistate);

    /* We know this is a newly created relation, so there are no indexes */
}

/*
 * intorel_shutdown --- executor end
 */
static void
intorel_shutdown(DestReceiver *self)
{
    DR_intorel *myState = (DR_intorel *) self;

    FreeBulkInsertState(myState->bistate);

    /* If we skipped using WAL, must heap_sync before commit */
    if (myState->hi_options & HEAP_INSERT_SKIP_WAL)
        heap_sync(myState->rel);

    /* close rel, but keep lock until commit */
    heap_close(myState->rel, NoLock);
    myState->rel = NULL;
}

/*
 * intorel_destroy --- release DestReceiver object
 */
static void
intorel_destroy(DestReceiver *self)
{
    pfree(self);
}