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/[email protected]

1 files changed, 3 insertions, 3 deletions

diff --git a/src/backend/commands/opclasscmds.c b/src/backend/commands/opclasscmds.c
index 822b331e0dc..ab51d1a4178 100644
--- a/src/backend/commands/opclasscmds.c
+++ b/src/backend/commands/opclasscmds.c
@@ -460,7 +460,7 @@ DefineOpClass(CreateOpClassStmt *stmt)
 	 */
 	foreach(l, stmt->items)
 	{
-		CreateOpClassItem *item = castNode(CreateOpClassItem, lfirst(l));
+		CreateOpClassItem *item = lfirst_node(CreateOpClassItem, l);
 		Oid			operOid;
 		Oid			funcOid;
 		Oid			sortfamilyOid;
@@ -834,7 +834,7 @@ AlterOpFamilyAdd(AlterOpFamilyStmt *stmt, Oid amoid, Oid opfamilyoid,
 	 */
 	foreach(l, items)
 	{
-		CreateOpClassItem *item = castNode(CreateOpClassItem, lfirst(l));
+		CreateOpClassItem *item = lfirst_node(CreateOpClassItem, l);
 		Oid			operOid;
 		Oid			funcOid;
 		Oid			sortfamilyOid;
@@ -959,7 +959,7 @@ AlterOpFamilyDrop(AlterOpFamilyStmt *stmt, Oid amoid, Oid opfamilyoid,
 	 */
 	foreach(l, items)
 	{
-		CreateOpClassItem *item = castNode(CreateOpClassItem, lfirst(l));
+		CreateOpClassItem *item = lfirst_node(CreateOpClassItem, l);
 		Oid			lefttype,
 					righttype;
 		OpFamilyMember *member;