Fix CREATE MATVIEW/CREATE TABLE AS ... WITH NO DATA to not plan the query.

Previously, these commands always planned the given query and went through
executor startup before deciding not to actually run the query if WITH NO
DATA is specified.  This behavior is problematic for pg_dump because it
may cause errors to be raised that we would rather not see before a
REFRESH MATERIALIZED VIEW command is issued.  See for example bug #13907
from Marian Krucina.  This change is not sufficient to fix that particular
bug, because we also need to tweak pg_dump to issue the REFRESH later,
but it's a necessary step on the way.

A user-visible side effect of doing things this way is that the returned
command tag for WITH NO DATA cases will now be "CREATE MATERIALIZED VIEW"
or "CREATE TABLE AS", not "SELECT 0".  We could preserve the old behavior
but it would take more code, and arguably that was just an implementation
artifact not intended behavior anyhow.

In 9.5 and HEAD, also get rid of the static variable CreateAsReladdr, which
was trouble waiting to happen; there is not any prohibition on nested
CREATE commands.

Back-patch to 9.3 where CREATE MATERIALIZED VIEW was introduced.

Michael Paquier and Tom Lane

Report: <20160202161407.2778.24659@wrigleys.postgresql.org>

1 files changed, 230 insertions, 132 deletions

diff --git a/src/backend/commands/createas.c b/src/backend/commands/createas.c
index 96806eed98b..4b1ba45ade4 100644
--- a/src/backend/commands/createas.c
+++ b/src/backend/commands/createas.c
@@ -10,7 +10,8 @@
  *
  * 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.
+ * we must return a tuples-processed count in the completionTag.  (We no
+ * longer do that for CTAS ... WITH NO DATA, however.)
  *
  * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
@@ -34,6 +35,8 @@
 #include "commands/tablecmds.h"
 #include "commands/view.h"
 #include "miscadmin.h"
+#include "nodes/makefuncs.h"
+#include "nodes/nodeFuncs.h"
 #include "parser/parse_clause.h"
 #include "rewrite/rewriteHandler.h"
 #include "storage/smgr.h"
@@ -55,6 +58,11 @@ typedef struct
 	BulkInsertState bistate;	/* bulk insert state */
 } DR_intorel;
 
+/* utility functions for CTAS definition creation */
+static Oid	create_ctas_internal(List *attrList, IntoClause *into);
+static Oid	create_ctas_nodata(List *tlist, IntoClause *into);
+
+/* DestReceiver routines for collecting data */
 static void intorel_startup(DestReceiver *self, int operation, TupleDesc typeinfo);
 static void intorel_receive(TupleTableSlot *slot, DestReceiver *self);
 static void intorel_shutdown(DestReceiver *self);
@@ -62,6 +70,150 @@ 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 Oid
+create_ctas_internal(List *attrList, IntoClause *into)
+{
+	CreateStmt *create = makeNode(CreateStmt);
+	bool		is_matview;
+	char		relkind;
+	Datum		toast_options;
+	static char *validnsps[] = HEAP_RELOPT_NAMESPACES;
+	Oid			intoRelationId;
+
+	/* 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 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.)
+	 */
+	intoRelationId = DefineRelation(create, relkind, InvalidOid);
+
+	/*
+	 * 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(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();
+	}
+
+	return intoRelationId;
+}
+
+
+/*
+ * 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 Oid
+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(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
  */
 void
@@ -78,7 +230,6 @@ ExecCreateTableAs(CreateTableAsStmt *stmt, const char *queryString,
 	List	   *rewritten;
 	PlannedStmt *plan;
 	QueryDesc  *queryDesc;
-	ScanDirection dir;
 
 	/*
 	 * Create the tuple receiver object and insert info it will need
@@ -117,70 +268,77 @@ ExecCreateTableAs(CreateTableAsStmt *stmt, const char *queryString,
 		save_nestlevel = NewGUCNestLevel();
 	}
 
-	/*
-	 * 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);
+	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.
+		 */
+		(void) create_ctas_nodata(query->targetList, into);
+	}
+	else
+	{
+		/*
+		 * 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));
 
-	/* plan the query */
-	plan = pg_plan_query(query, 0, params);
+		/* SELECT should never rewrite to more or less than one SELECT query */
+		if (list_length(rewritten) != 1)
+			elog(ERROR, "unexpected rewrite result for %s",
+				 is_matview ? "CREATE MATERIALIZED VIEW" :
+				 "CREATE TABLE AS SELECT");
+		query = (Query *) linitial(rewritten);
+		Assert(query->commandType == CMD_SELECT);
 
-	/*
-	 * 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();
+		/* plan the query */
+		plan = pg_plan_query(query, 0, params);
 
-	/* Create a QueryDesc, redirecting output to our tuple receiver */
-	queryDesc = CreateQueryDesc(plan, queryString,
-								GetActiveSnapshot(), InvalidSnapshot,
-								dest, params, 0);
+		/*
+		 * 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();
 
-	/* call ExecutorStart to prepare the plan for execution */
-	ExecutorStart(queryDesc, GetIntoRelEFlags(into));
+		/* Create a QueryDesc, redirecting output to our tuple receiver */
+		queryDesc = CreateQueryDesc(plan, queryString,
+									GetActiveSnapshot(), InvalidSnapshot,
+									dest, params, 0);
 
-	/*
-	 * 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;
+		/* call ExecutorStart to prepare the plan for execution */
+		ExecutorStart(queryDesc, GetIntoRelEFlags(into));
 
-	/* run the plan */
-	ExecutorRun(queryDesc, dir, 0L);
+		/* run the plan to completion */
+		ExecutorRun(queryDesc, ForwardScanDirection, 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);
+		/* 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);
+		/* and clean up */
+		ExecutorFinish(queryDesc);
+		ExecutorEnd(queryDesc);
 
-	FreeQueryDesc(queryDesc);
+		FreeQueryDesc(queryDesc);
 
-	PopActiveSnapshot();
+		PopActiveSnapshot();
+	}
 
 	if (is_matview)
 	{
@@ -257,14 +415,12 @@ intorel_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
 	IntoClause *into = myState->into;
 	bool		is_matview;
 	char		relkind;
-	CreateStmt *create;
+	List	   *attrList;
 	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 */
 
@@ -273,62 +429,31 @@ intorel_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
 	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.)
 	 */
+	attrList = NIL;
 	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);
+		ColumnDef  *col;
+		char	   *colname;
 
 		if (lc)
 		{
-			col->colname = strVal(lfirst(lc));
+			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;
-		col->location = -1;
-
-		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;
+			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
@@ -337,14 +462,15 @@ intorel_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
 		 * collation rather than complaining.)
 		 */
 		if (!OidIsValid(col->collOid) &&
-			type_is_collatable(coltype->typeOid))
+			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(coltype->typeOid)),
+							col->colname,
+							format_type_be(col->typeName->typeOid)),
 					 errhint("Use the COLLATE clause to set the collation explicitly.")));
 
-		create->tableElts = lappend(create->tableElts, col);
+		attrList = lappend(attrList, col);
 	}
 
 	if (lc != NULL)
@@ -355,35 +481,7 @@ intorel_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
 	/*
 	 * Actually create the target table
 	 */
-	intoRelationId = DefineRelation(create, relkind, InvalidOid);
-
-	/*
-	 * 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(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();
-	}
+	intoRelationId = create_ctas_internal(attrList, into);
 
 	/*
 	 * Finally we can open the target table