Improve castNode notation by introducing list-extraction-specific variants.

This extends the castNode() notation introduced by commit 5bcab1114 to
provide, in one step, extraction of a list cell's pointer and coercion to
a concrete node type.  For example, "lfirst_node(Foo, lc)" is the same
as "castNode(Foo, lfirst(lc))".  Almost half of the uses of castNode
that have appeared so far include a list extraction call, so this is
pretty widely useful, and it saves a few more keystrokes compared to the
old way.

As with the previous patch, back-patch the addition of these macros to
pg_list.h, so that the notation will be available when back-patching.

Patch by me, after an idea of Andrew Gierth's.

Discussion: https://postgr.es/m/14197.1491841216@sss.pgh.pa.us

1 files changed, 5 insertions, 5 deletions

diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index cb860ec4e51..4dcb7138e7e 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -2367,7 +2367,7 @@ view_cols_are_auto_updatable(Query *viewquery,
 	 * there should be a single base relation.
 	 */
 	Assert(list_length(viewquery->jointree->fromlist) == 1);
-	rtr = castNode(RangeTblRef, linitial(viewquery->jointree->fromlist));
+	rtr = linitial_node(RangeTblRef, viewquery->jointree->fromlist);
 
 	/* Initialize the optional return values */
 	if (updatable_cols != NULL)
@@ -2619,7 +2619,7 @@ adjust_view_column_set(Bitmapset *cols, List *targetlist)
 
 			foreach(lc, targetlist)
 			{
-				TargetEntry *tle = (TargetEntry *) lfirst(lc);
+				TargetEntry *tle = lfirst_node(TargetEntry, lc);
 				Var		   *var;
 
 				if (tle->resjunk)
@@ -2806,7 +2806,7 @@ rewriteTargetView(Query *parsetree, Relation view)
 	 * view contains a single base relation.
 	 */
 	Assert(list_length(viewquery->jointree->fromlist) == 1);
-	rtr = castNode(RangeTblRef, linitial(viewquery->jointree->fromlist));
+	rtr = linitial_node(RangeTblRef, viewquery->jointree->fromlist);
 
 	base_rt_index = rtr->rtindex;
 	base_rte = rt_fetch(base_rt_index, viewquery->rtable);
@@ -3162,7 +3162,7 @@ RewriteQuery(Query *parsetree, List *rewrite_events)
 	 */
 	foreach(lc1, parsetree->cteList)
 	{
-		CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc1);
+		CommonTableExpr *cte = lfirst_node(CommonTableExpr, lc1);
 		Query	   *ctequery = castNode(Query, cte->ctequery);
 		List	   *newstuff;
 
@@ -3179,7 +3179,7 @@ RewriteQuery(Query *parsetree, List *rewrite_events)
 		if (list_length(newstuff) == 1)
 		{
 			/* Push the single Query back into the CTE node */
-			ctequery = castNode(Query, linitial(newstuff));
+			ctequery = linitial_node(Query, newstuff);
 			/* WITH queries should never be canSetTag */
 			Assert(!ctequery->canSetTag);
 			cte->ctequery = (Node *) ctequery;