Use castNode() in a bunch of statement-list-related code.

When I wrote commit ab1f0c822, I really missed the castNode() macro that
Peter E. had proposed shortly before.  This back-fills the uses I would
have put it to.  It's probably not all that significant, but there are
more assertions here than there were before, and conceivably they will
help catch any bugs associated with those representation changes.

I left behind a number of usages like "(Query *) copyObject(query_var)".
Those could have been converted as well, but Peter has proposed another
notational improvement that would handle copyObject cases automatically,
so I let that be for now.

20 files changed, 63 insertions, 90 deletions

diff --git a/src/backend/catalog/pg_proc.c b/src/backend/catalog/pg_proc.c
index bb83a9a7c6..6ab849c6ef 100644
--- a/src/backend/catalog/pg_proc.c
+++ b/src/backend/catalog/pg_proc.c
@@ -930,7 +930,7 @@ fmgr_sql_validator(PG_FUNCTION_ARGS)
 			querytree_list = NIL;
 			foreach(lc, raw_parsetree_list)
 			{
-				RawStmt    *parsetree = (RawStmt *) lfirst(lc);
+				RawStmt    *parsetree = castNode(RawStmt, lfirst(lc));
 				List	   *querytree_sublist;
 
 				querytree_sublist = pg_analyze_and_rewrite_params(parsetree,
diff --git a/src/backend/commands/createas.c b/src/backend/commands/createas.c
index 02cfcd182d..646a88409f 100644
--- a/src/backend/commands/createas.c
+++ b/src/backend/commands/createas.c
@@ -322,7 +322,7 @@ ExecCreateTableAs(CreateTableAsStmt *stmt, const char *queryString,
 			elog(ERROR, "unexpected rewrite result for %s",
 				 is_matview ? "CREATE MATERIALIZED VIEW" :
 				 "CREATE TABLE AS SELECT");
-		query = (Query *) linitial(rewritten);
+		query = castNode(Query, linitial(rewritten));
 		Assert(query->commandType == CMD_SELECT);
 
 		/* plan the query --- note we disallow parallelism */
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 5d61a0195e..0a67be031b 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -224,8 +224,7 @@ ExplainQuery(ParseState *pstate, ExplainStmt *stmt, const char *queryString,
 	 * executed repeatedly.  (See also the same hack in DECLARE CURSOR and
 	 * PREPARE.)  XXX FIXME someday.
 	 */
-	Assert(IsA(stmt->query, Query));
-	rewritten = QueryRewrite((Query *) copyObject(stmt->query));
+	rewritten = QueryRewrite(castNode(Query, copyObject(stmt->query)));
 
 	/* emit opening boilerplate */
 	ExplainBeginOutput(es);
@@ -246,7 +245,7 @@ ExplainQuery(ParseState *pstate, ExplainStmt *stmt, const char *queryString,
 		/* Explain every plan */
 		foreach(l, rewritten)
 		{
-			ExplainOneQuery((Query *) lfirst(l),
+			ExplainOneQuery(castNode(Query, lfirst(l)),
 							CURSOR_OPT_PARALLEL_OK, NULL, es,
 							queryString, params);
 
@@ -395,10 +394,9 @@ ExplainOneUtility(Node *utilityStmt, IntoClause *into, ExplainState *es,
 		CreateTableAsStmt *ctas = (CreateTableAsStmt *) utilityStmt;
 		List	   *rewritten;
 
-		Assert(IsA(ctas->query, Query));
-		rewritten = QueryRewrite((Query *) copyObject(ctas->query));
+		rewritten = QueryRewrite(castNode(Query, copyObject(ctas->query)));
 		Assert(list_length(rewritten) == 1);
-		ExplainOneQuery((Query *) linitial(rewritten),
+		ExplainOneQuery(castNode(Query, linitial(rewritten)),
 						0, ctas->into, es,
 						queryString, params);
 	}
@@ -415,10 +413,9 @@ ExplainOneUtility(Node *utilityStmt, IntoClause *into, ExplainState *es,
 		DeclareCursorStmt *dcs = (DeclareCursorStmt *) utilityStmt;
 		List	   *rewritten;
 
-		Assert(IsA(dcs->query, Query));
-		rewritten = QueryRewrite((Query *) copyObject(dcs->query));
+		rewritten = QueryRewrite(castNode(Query, copyObject(dcs->query)));
 		Assert(list_length(rewritten) == 1);
-		ExplainOneQuery((Query *) linitial(rewritten),
+		ExplainOneQuery(castNode(Query, linitial(rewritten)),
 						dcs->options, NULL, es,
 						queryString, params);
 	}
diff --git a/src/backend/commands/extension.c b/src/backend/commands/extension.c
index 554fdc46b4..9680d986a0 100644
--- a/src/backend/commands/extension.c
+++ b/src/backend/commands/extension.c
@@ -713,7 +713,7 @@ execute_sql_string(const char *sql, const char *filename)
 	 */
 	foreach(lc1, raw_parsetree_list)
 	{
-		RawStmt    *parsetree = (RawStmt *) lfirst(lc1);
+		RawStmt    *parsetree = castNode(RawStmt, lfirst(lc1));
 		List	   *stmt_list;
 		ListCell   *lc2;
 
@@ -725,7 +725,7 @@ execute_sql_string(const char *sql, const char *filename)
 
 		foreach(lc2, stmt_list)
 		{
-			PlannedStmt *stmt = (PlannedStmt *) lfirst(lc2);
+			PlannedStmt *stmt = castNode(PlannedStmt, lfirst(lc2));
 
 			CommandCounterIncrement();
 
diff --git a/src/backend/commands/foreigncmds.c b/src/backend/commands/foreigncmds.c
index 476a023ec5..6ff8b6998b 100644
--- a/src/backend/commands/foreigncmds.c
+++ b/src/backend/commands/foreigncmds.c
@@ -1572,7 +1572,7 @@ ImportForeignSchema(ImportForeignSchemaStmt *stmt)
 		 */
 		foreach(lc2, raw_parsetree_list)
 		{
-			RawStmt    *rs = (RawStmt *) lfirst(lc2);
+			RawStmt    *rs = castNode(RawStmt, lfirst(lc2));
 			CreateForeignTableStmt *cstmt = (CreateForeignTableStmt *) rs->stmt;
 			PlannedStmt *pstmt;
 
diff --git a/src/backend/commands/portalcmds.c b/src/backend/commands/portalcmds.c
index 1d3e39299b..29d0430dd8 100644
--- a/src/backend/commands/portalcmds.c
+++ b/src/backend/commands/portalcmds.c
@@ -42,14 +42,12 @@ void
 PerformCursorOpen(DeclareCursorStmt *cstmt, ParamListInfo params,
 				  const char *queryString, bool isTopLevel)
 {
-	Query	   *query = (Query *) cstmt->query;
+	Query	   *query = castNode(Query, cstmt->query);
 	List	   *rewritten;
 	PlannedStmt *plan;
 	Portal		portal;
 	MemoryContext oldContext;
 
-	Assert(IsA(query, Query));	/* else parse analysis wasn't done */
-
 	/*
 	 * Disallow empty-string cursor name (conflicts with protocol-level
 	 * unnamed portal).
@@ -85,7 +83,7 @@ PerformCursorOpen(DeclareCursorStmt *cstmt, ParamListInfo params,
 	if (list_length(rewritten) != 1)
 		elog(ERROR, "non-SELECT statement in DECLARE CURSOR");
 
-	query = (Query *) linitial(rewritten);
+	query = castNode(Query, linitial(rewritten));
 
 	if (query->commandType != CMD_SELECT)
 		elog(ERROR, "non-SELECT statement in DECLARE CURSOR");
diff --git a/src/backend/commands/prepare.c b/src/backend/commands/prepare.c
index 7d7e3daf1e..7b61da3ef0 100644
--- a/src/backend/commands/prepare.c
+++ b/src/backend/commands/prepare.c
@@ -265,8 +265,7 @@ ExecuteQuery(ExecuteStmt *stmt, IntoClause *intoClause,
 			ereport(ERROR,
 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 					 errmsg("prepared statement is not a SELECT")));
-		pstmt = (PlannedStmt *) linitial(plan_list);
-		Assert(IsA(pstmt, PlannedStmt));
+		pstmt = castNode(PlannedStmt, linitial(plan_list));
 		if (pstmt->commandType != CMD_SELECT)
 			ereport(ERROR,
 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
@@ -670,9 +669,8 @@ ExplainExecuteQuery(ExecuteStmt *execstmt, IntoClause *into, ExplainState *es,
 	/* Explain each query */
 	foreach(p, plan_list)
 	{
-		PlannedStmt *pstmt = (PlannedStmt *) lfirst(p);
+		PlannedStmt *pstmt = castNode(PlannedStmt, lfirst(p));
 
-		Assert(IsA(pstmt, PlannedStmt));
 		if (pstmt->commandType != CMD_UTILITY)
 			ExplainOnePlan(pstmt, into, es, query_string, paramLI, NULL);
 		else
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 04b5d9a943..90f2f7f00e 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -9281,7 +9281,7 @@ ATPostAlterTypeParse(Oid oldId, Oid oldRelId, Oid refRelId, char *cmd,
 	querytree_list = NIL;
 	foreach(list_item, raw_parsetree_list)
 	{
-		RawStmt    *rs = (RawStmt *) lfirst(list_item);
+		RawStmt    *rs = castNode(RawStmt, lfirst(list_item));
 		Node	   *stmt = rs->stmt;
 
 		if (IsA(stmt, IndexStmt))
diff --git a/src/backend/executor/functions.c b/src/backend/executor/functions.c
index 15c709139a..2d49a65650 100644
--- a/src/backend/executor/functions.c
+++ b/src/backend/executor/functions.c
@@ -707,7 +707,7 @@ init_sql_fcache(FmgrInfo *finfo, Oid collation, bool lazyEvalOK)
 	flat_query_list = NIL;
 	foreach(lc, raw_parsetree_list)
 	{
-		RawStmt    *parsetree = (RawStmt *) lfirst(lc);
+		RawStmt    *parsetree = castNode(RawStmt, lfirst(lc));
 		List	   *queryTree_sublist;
 
 		queryTree_sublist = pg_analyze_and_rewrite_params(parsetree,
@@ -1551,7 +1551,7 @@ check_sql_fn_retval(Oid func_id, Oid rettype, List *queryTreeList,
 	parse = NULL;
 	foreach(lc, queryTreeList)
 	{
-		Query	   *q = (Query *) lfirst(lc);
+		Query	   *q = castNode(Query, lfirst(lc));
 
 		if (q->canSetTag)
 			parse = q;
diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index 7bd37283b7..55f97b14e6 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -1232,9 +1232,9 @@ SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
 	if (!(portal->cursorOptions & (CURSOR_OPT_SCROLL | CURSOR_OPT_NO_SCROLL)))
 	{
 		if (list_length(stmt_list) == 1 &&
-		 ((PlannedStmt *) linitial(stmt_list))->commandType != CMD_UTILITY &&
-			((PlannedStmt *) linitial(stmt_list))->rowMarks == NIL &&
-			ExecSupportsBackwardScan(((PlannedStmt *) linitial(stmt_list))->planTree))
+			castNode(PlannedStmt, linitial(stmt_list))->commandType != CMD_UTILITY &&
+			castNode(PlannedStmt, linitial(stmt_list))->rowMarks == NIL &&
+			ExecSupportsBackwardScan(castNode(PlannedStmt, linitial(stmt_list))->planTree))
 			portal->cursorOptions |= CURSOR_OPT_SCROLL;
 		else
 			portal->cursorOptions |= CURSOR_OPT_NO_SCROLL;
@@ -1248,8 +1248,8 @@ SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
 	if (portal->cursorOptions & CURSOR_OPT_SCROLL)
 	{
 		if (list_length(stmt_list) == 1 &&
-		 ((PlannedStmt *) linitial(stmt_list))->commandType != CMD_UTILITY &&
-			((PlannedStmt *) linitial(stmt_list))->rowMarks != NIL)
+			castNode(PlannedStmt, linitial(stmt_list))->commandType != CMD_UTILITY &&
+			castNode(PlannedStmt, linitial(stmt_list))->rowMarks != NIL)
 			ereport(ERROR,
 					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 					 errmsg("DECLARE SCROLL CURSOR ... FOR UPDATE/SHARE is not supported"),
@@ -1270,7 +1270,7 @@ SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
 
 		foreach(lc, stmt_list)
 		{
-			PlannedStmt *pstmt = (PlannedStmt *) lfirst(lc);
+			PlannedStmt *pstmt = castNode(PlannedStmt, lfirst(lc));
 
 			if (!CommandIsReadOnly(pstmt))
 			{
@@ -1757,7 +1757,7 @@ _SPI_prepare_plan(const char *src, SPIPlanPtr plan)
 
 	foreach(list_item, raw_parsetree_list)
 	{
-		RawStmt    *parsetree = (RawStmt *) lfirst(list_item);
+		RawStmt    *parsetree = castNode(RawStmt, lfirst(list_item));
 		List	   *stmt_list;
 		CachedPlanSource *plansource;
 
@@ -1859,7 +1859,7 @@ _SPI_prepare_oneshot_plan(const char *src, SPIPlanPtr plan)
 
 	foreach(list_item, raw_parsetree_list)
 	{
-		RawStmt    *parsetree = (RawStmt *) lfirst(list_item);
+		RawStmt    *parsetree = castNode(RawStmt, lfirst(list_item));
 		CachedPlanSource *plansource;
 
 		plansource = CreateOneShotCachedPlan(parsetree,
@@ -2018,7 +2018,7 @@ _SPI_execute_plan(SPIPlanPtr plan, ParamListInfo paramLI,
 
 		foreach(lc2, stmt_list)
 		{
-			PlannedStmt *stmt = (PlannedStmt *) lfirst(lc2);
+			PlannedStmt *stmt = castNode(PlannedStmt, lfirst(lc2));
 			bool		canSetTag = stmt->canSetTag;
 			DestReceiver *dest;
 
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index a8e35feccc..a4edea08a3 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -788,7 +788,7 @@ stmtmulti:	stmtmulti ';' stmt
 					if ($1 != NIL)
 					{
 						/* update length of previous stmt */
-						updateRawStmtEnd((RawStmt *) llast($1), @2);
+						updateRawStmtEnd(castNode(RawStmt, llast($1)), @2);
 					}
 					if ($3 != NULL)
 						$$ = lappend($1, makeRawStmt($3, @2 + 1));
diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index c43ef19df5..4b73272417 100644
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -1502,8 +1502,7 @@ transformMultiAssignRef(ParseState *pstate, MultiAssignRef *maref)
 			sublink = (SubLink *) transformExprRecurse(pstate,
 													   (Node *) sublink);
 
-			qtree = (Query *) sublink->subselect;
-			Assert(IsA(qtree, Query));
+			qtree = castNode(Query, sublink->subselect);
 
 			/* Check subquery returns required number of columns */
 			if (count_nonjunk_tlist_entries(qtree->targetList) != maref->ncolumns)
@@ -1578,8 +1577,7 @@ transformMultiAssignRef(ParseState *pstate, MultiAssignRef *maref)
 
 		sublink = (SubLink *) tle->expr;
 		Assert(sublink->subLinkType == MULTIEXPR_SUBLINK);
-		qtree = (Query *) sublink->subselect;
-		Assert(IsA(qtree, Query));
+		qtree = castNode(Query, sublink->subselect);
 
 		/* Build a Param representing the current subquery output column */
 		tle = (TargetEntry *) list_nth(qtree->targetList, maref->colno - 1);
diff --git a/src/backend/parser/parse_type.c b/src/backend/parser/parse_type.c
index 6660929dec..8feec0b72b 100644
--- a/src/backend/parser/parse_type.c
+++ b/src/backend/parser/parse_type.c
@@ -720,7 +720,7 @@ typeStringToTypeName(const char *str)
 	 */
 	if (list_length(raw_parsetree_list) != 1)
 		goto fail;
-	stmt = (SelectStmt *) ((RawStmt *) linitial(raw_parsetree_list))->stmt;
+	stmt = (SelectStmt *) castNode(RawStmt, linitial(raw_parsetree_list))->stmt;
 	if (stmt == NULL ||
 		!IsA(stmt, SelectStmt) ||
 		stmt->distinctClause != NIL ||
diff --git a/src/backend/rewrite/rewriteDefine.c b/src/backend/rewrite/rewriteDefine.c
index 864d45ff12..481868bf53 100644
--- a/src/backend/rewrite/rewriteDefine.c
+++ b/src/backend/rewrite/rewriteDefine.c
@@ -173,7 +173,7 @@ InsertRule(char *rulname,
 	if (event_qual != NULL)
 	{
 		/* Find query containing OLD/NEW rtable entries */
-		Query	   *qry = (Query *) linitial(action);
+		Query	   *qry = castNode(Query, linitial(action));
 
 		qry = getInsertSelectQuery(qry, NULL);
 		recordDependencyOnExpr(&myself, event_qual, qry->rtable,
@@ -286,7 +286,7 @@ DefineQueryRewrite(char *rulename,
 	 */
 	foreach(l, action)
 	{
-		query = (Query *) lfirst(l);
+		query = castNode(Query, lfirst(l));
 		if (query->resultRelation == 0)
 			continue;
 		/* Don't be fooled by INSERT/SELECT */
@@ -328,7 +328,7 @@ DefineQueryRewrite(char *rulename,
 		/*
 		 * ... the one action must be a SELECT, ...
 		 */
-		query = (Query *) linitial(action);
+		query = castNode(Query, linitial(action));
 		if (!is_instead ||
 			query->commandType != CMD_SELECT)
 			ereport(ERROR,
@@ -482,7 +482,7 @@ DefineQueryRewrite(char *rulename,
 
 		foreach(l, action)
 		{
-			query = (Query *) lfirst(l);
+			query = castNode(Query, lfirst(l));
 
 			if (!query->returningList)
 				continue;
@@ -813,7 +813,7 @@ setRuleCheckAsUser_Query(Query *qry, Oid userid)
 	{
 		CommonTableExpr *cte = (CommonTableExpr *) lfirst(l);
 
-		setRuleCheckAsUser_Query((Query *) cte->ctequery, userid);
+		setRuleCheckAsUser_Query(castNode(Query, cte->ctequery), userid);
 	}
 
 	/* If there are sublinks, search for them and process their RTEs */
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 62d49c8625..b07d6c6cb9 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -962,7 +962,7 @@ exec_simple_query(const char *query_string)
 	 */
 	foreach(parsetree_item, parsetree_list)
 	{
-		RawStmt    *parsetree = (RawStmt *) lfirst(parsetree_item);
+		RawStmt    *parsetree = castNode(RawStmt, lfirst(parsetree_item));
 		bool		snapshot_set = false;
 		const char *commandTag;
 		char		completionTag[COMPLETION_TAG_BUFSIZE];
@@ -1286,7 +1286,7 @@ exec_parse_message(const char *query_string,	/* string to execute */
 		bool		snapshot_set = false;
 		int			i;
 
-		raw_parse_tree = (RawStmt *) linitial(parsetree_list);
+		raw_parse_tree = castNode(RawStmt, linitial(parsetree_list));
 
 		/*
 		 * Get the command name for possible use in status display.
@@ -2148,7 +2148,7 @@ errdetail_execute(List *raw_parsetree_list)
 
 	foreach(parsetree_item, raw_parsetree_list)
 	{
-		RawStmt    *parsetree = (RawStmt *) lfirst(parsetree_item);
+		RawStmt    *parsetree = castNode(RawStmt, lfirst(parsetree_item));
 
 		if (IsA(parsetree->stmt, ExecuteStmt))
 		{
@@ -2502,9 +2502,8 @@ IsTransactionExitStmtList(List *pstmts)
 {
 	if (list_length(pstmts) == 1)
 	{
-		PlannedStmt *pstmt = (PlannedStmt *) linitial(pstmts);
+		PlannedStmt *pstmt = castNode(PlannedStmt, linitial(pstmts));
 
-		Assert(IsA(pstmt, PlannedStmt));
 		if (pstmt->commandType == CMD_UTILITY &&
 			IsTransactionExitStmt(pstmt->utilityStmt))
 			return true;
@@ -2518,9 +2517,8 @@ IsTransactionStmtList(List *pstmts)
 {
 	if (list_length(pstmts) == 1)
 	{
-		PlannedStmt *pstmt = (PlannedStmt *) linitial(pstmts);
+		PlannedStmt *pstmt = castNode(PlannedStmt, linitial(pstmts));
 
-		Assert(IsA(pstmt, PlannedStmt));
 		if (pstmt->commandType == CMD_UTILITY &&
 			IsA(pstmt->utilityStmt, TransactionStmt))
 			return true;
diff --git a/src/backend/tcop/pquery.c b/src/backend/tcop/pquery.c
index 704be399cf..e64ea2ed76 100644
--- a/src/backend/tcop/pquery.c
+++ b/src/backend/tcop/pquery.c
@@ -487,7 +487,7 @@ PortalStart(Portal portal, ParamListInfo params,
 				 * Create QueryDesc in portal's context; for the moment, set
 				 * the destination to DestNone.
 				 */
-				queryDesc = CreateQueryDesc((PlannedStmt *) linitial(portal->stmts),
+				queryDesc = CreateQueryDesc(castNode(PlannedStmt, linitial(portal->stmts)),
 											portal->sourceText,
 											GetActiveSnapshot(),
 											InvalidSnapshot,
@@ -1020,7 +1020,7 @@ FillPortalStore(Portal portal, bool isTopLevel)
 			break;
 
 		case PORTAL_UTIL_SELECT:
-			PortalRunUtility(portal, (PlannedStmt *) linitial(portal->stmts),
+			PortalRunUtility(portal, castNode(PlannedStmt, linitial(portal->stmts)),
 							 isTopLevel, true, treceiver, completionTag);
 			break;
 
@@ -1215,7 +1215,7 @@ PortalRunMulti(Portal portal,
 	 */
 	foreach(stmtlist_item, portal->stmts)
 	{
-		PlannedStmt *pstmt = (PlannedStmt *) lfirst(stmtlist_item);
+		PlannedStmt *pstmt = castNode(PlannedStmt, lfirst(stmtlist_item));
 
 		/*
 		 * If we got a cancel signal in prior command, quit
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 0306247177..801a9634dc 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -1829,22 +1829,19 @@ UtilityContainsQuery(Node *parsetree)
 	switch (nodeTag(parsetree))
 	{
 		case T_DeclareCursorStmt:
-			qry = (Query *) ((DeclareCursorStmt *) parsetree)->query;
-			Assert(IsA(qry, Query));
+			qry = castNode(Query, ((DeclareCursorStmt *) parsetree)->query);
 			if (qry->commandType == CMD_UTILITY)
 				return UtilityContainsQuery(qry->utilityStmt);
 			return qry;
 
 		case T_ExplainStmt:
-			qry = (Query *) ((ExplainStmt *) parsetree)->query;
-			Assert(IsA(qry, Query));
+			qry = castNode(Query, ((ExplainStmt *) parsetree)->query);
 			if (qry->commandType == CMD_UTILITY)
 				return UtilityContainsQuery(qry->utilityStmt);
 			return qry;
 
 		case T_CreateTableAsStmt:
-			qry = (Query *) ((CreateTableAsStmt *) parsetree)->query;
-			Assert(IsA(qry, Query));
+			qry = castNode(Query, ((CreateTableAsStmt *) parsetree)->query);
 			if (qry->commandType == CMD_UTILITY)
 				return UtilityContainsQuery(qry->utilityStmt);
 			return qry;
diff --git a/src/backend/utils/cache/plancache.c b/src/backend/utils/cache/plancache.c
index c31c603fbf..dffc92762b 100644
--- a/src/backend/utils/cache/plancache.c
+++ b/src/backend/utils/cache/plancache.c
@@ -975,7 +975,7 @@ BuildCachedPlan(CachedPlanSource *plansource, List *qlist,
 	is_transient = false;
 	foreach(lc, plist)
 	{
-		PlannedStmt *plannedstmt = (PlannedStmt *) lfirst(lc);
+		PlannedStmt *plannedstmt = castNode(PlannedStmt, lfirst(lc));
 
 		if (plannedstmt->commandType == CMD_UTILITY)
 			continue;			/* Ignore utility statements */
@@ -1070,7 +1070,7 @@ cached_plan_cost(CachedPlan *plan, bool include_planner)
 
 	foreach(lc, plan->stmt_list)
 	{
-		PlannedStmt *plannedstmt = (PlannedStmt *) lfirst(lc);
+		PlannedStmt *plannedstmt = castNode(PlannedStmt, lfirst(lc));
 
 		if (plannedstmt->commandType == CMD_UTILITY)
 			continue;			/* Ignore utility statements */
@@ -1457,9 +1457,7 @@ QueryListGetPrimaryStmt(List *stmts)
 
 	foreach(lc, stmts)
 	{
-		Query	   *stmt = (Query *) lfirst(lc);
-
-		Assert(IsA(stmt, Query));
+		Query	   *stmt = castNode(Query, lfirst(lc));
 
 		if (stmt->canSetTag)
 			return stmt;
@@ -1478,12 +1476,10 @@ AcquireExecutorLocks(List *stmt_list, bool acquire)
 
 	foreach(lc1, stmt_list)
 	{
-		PlannedStmt *plannedstmt = (PlannedStmt *) lfirst(lc1);
+		PlannedStmt *plannedstmt = castNode(PlannedStmt, lfirst(lc1));
 		int			rt_index;
 		ListCell   *lc2;
 
-		Assert(IsA(plannedstmt, PlannedStmt));
-
 		if (plannedstmt->commandType == CMD_UTILITY)
 		{
 			/*
@@ -1549,9 +1545,7 @@ AcquirePlannerLocks(List *stmt_list, bool acquire)
 
 	foreach(lc, stmt_list)
 	{
-		Query	   *query = (Query *) lfirst(lc);
-
-		Assert(IsA(query, Query));
+		Query	   *query = castNode(Query, lfirst(lc));
 
 		if (query->commandType == CMD_UTILITY)
 		{
@@ -1618,9 +1612,9 @@ ScanQueryForLocks(Query *parsetree, bool acquire)
 	/* Recurse into subquery-in-WITH */
 	foreach(lc, parsetree->cteList)
 	{
-		CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc);
+		CommonTableExpr *cte = castNode(CommonTableExpr, lfirst(lc));
 
-		ScanQueryForLocks((Query *) cte->ctequery, acquire);
+		ScanQueryForLocks(castNode(Query, cte->ctequery), acquire);
 	}
 
 	/*
@@ -1648,7 +1642,7 @@ ScanQueryWalker(Node *node, bool *acquire)
 		SubLink    *sub = (SubLink *) node;
 
 		/* Do what we came for */
-		ScanQueryForLocks((Query *) sub->subselect, *acquire);
+		ScanQueryForLocks(castNode(Query, sub->subselect), *acquire);
 		/* Fall through to process lefthand args of SubLink */
 	}
 
@@ -1676,8 +1670,7 @@ PlanCacheComputeResultDesc(List *stmt_list)
 	{
 		case PORTAL_ONE_SELECT:
 		case PORTAL_ONE_MOD_WITH:
-			query = (Query *) linitial(stmt_list);
-			Assert(IsA(query, Query));
+			query = castNode(Query, linitial(stmt_list));
 			return ExecCleanTypeFromTL(query->targetList, false);
 
 		case PORTAL_ONE_RETURNING:
@@ -1686,8 +1679,7 @@ PlanCacheComputeResultDesc(List *stmt_list)
 			return ExecCleanTypeFromTL(query->returningList, false);
 
 		case PORTAL_UTIL_SELECT:
-			query = (Query *) linitial(stmt_list);
-			Assert(IsA(query, Query));
+			query = castNode(Query, linitial(stmt_list));
 			Assert(query->utilityStmt);
 			return UtilityTupleDescriptor(query->utilityStmt);
 
@@ -1744,7 +1736,7 @@ PlanCacheRelCallback(Datum arg, Oid relid)
 
 			foreach(lc, plansource->gplan->stmt_list)
 			{
-				PlannedStmt *plannedstmt = (PlannedStmt *) lfirst(lc);
+				PlannedStmt *plannedstmt = castNode(PlannedStmt, lfirst(lc));
 
 				if (plannedstmt->commandType == CMD_UTILITY)
 					continue;	/* Ignore utility statements */
@@ -1817,7 +1809,7 @@ PlanCacheFuncCallback(Datum arg, int cacheid, uint32 hashvalue)
 		{
 			foreach(lc, plansource->gplan->stmt_list)
 			{
-				PlannedStmt *plannedstmt = (PlannedStmt *) lfirst(lc);
+				PlannedStmt *plannedstmt = castNode(PlannedStmt, lfirst(lc));
 				ListCell   *lc3;
 
 				if (plannedstmt->commandType == CMD_UTILITY)
@@ -1890,9 +1882,8 @@ ResetPlanCache(void)
 		 */
 		foreach(lc, plansource->query_list)
 		{
-			Query	   *query = (Query *) lfirst(lc);
+			Query	   *query = castNode(Query, lfirst(lc));
 
-			Assert(IsA(query, Query));
 			if (query->commandType != CMD_UTILITY ||
 				UtilityContainsQuery(query->utilityStmt))
 			{
diff --git a/src/backend/utils/mmgr/portalmem.c b/src/backend/utils/mmgr/portalmem.c
index e8ebc4684c..3a3259bae2 100644
--- a/src/backend/utils/mmgr/portalmem.c
+++ b/src/backend/utils/mmgr/portalmem.c
@@ -153,9 +153,7 @@ PortalGetPrimaryStmt(Portal portal)
 
 	foreach(lc, portal->stmts)
 	{
-		PlannedStmt *stmt = (PlannedStmt *) lfirst(lc);
-
-		Assert(IsA(stmt, PlannedStmt));
+		PlannedStmt *stmt = castNode(PlannedStmt, lfirst(lc));
 
 		if (stmt->canSetTag)
 			return stmt;
diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index b48146a362..6fc3db07fe 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -3634,9 +3634,8 @@ exec_stmt_execsql(PLpgSQL_execstate *estate,
 
 			foreach(l2, plansource->query_list)
 			{
-				Query	   *q = (Query *) lfirst(l2);
+				Query	   *q = castNode(Query, lfirst(l2));
 
-				Assert(IsA(q, Query));
 				if (q->canSetTag)
 				{
 					if (q->commandType == CMD_INSERT ||
@@ -6825,8 +6824,7 @@ exec_simple_recheck_plan(PLpgSQL_expr *expr, CachedPlan *cplan)
 	 */
 	if (list_length(cplan->stmt_list) != 1)
 		return;
-	stmt = (PlannedStmt *) linitial(cplan->stmt_list);
-	Assert(IsA(stmt, PlannedStmt));
+	stmt = castNode(PlannedStmt, linitial(cplan->stmt_list));
 
 	/*
 	 * 2. It must be a RESULT plan --> no scan's required