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

3 files changed, 9 insertions, 9 deletions

diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 1f510c28198..52643d0ad61 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -757,7 +757,7 @@ extract_nonindex_conditions(List *qual_clauses, List *indexquals)
 
 	foreach(lc, qual_clauses)
 	{
-		RestrictInfo *rinfo = castNode(RestrictInfo, lfirst(lc));
+		RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
 
 		if (rinfo->pseudoconstant)
 			continue;			/* we may drop pseudoconstants here */
@@ -1990,7 +1990,7 @@ cost_windowagg(Path *path, PlannerInfo *root,
 	 */
 	foreach(lc, windowFuncs)
 	{
-		WindowFunc *wfunc = castNode(WindowFunc, lfirst(lc));
+		WindowFunc *wfunc = lfirst_node(WindowFunc, lc);
 		Cost		wfunccost;
 		QualCost	argcosts;
 
@@ -3066,7 +3066,7 @@ final_cost_hashjoin(PlannerInfo *root, HashPath *path,
 		innerbucketsize = 1.0;
 		foreach(hcl, hashclauses)
 		{
-			RestrictInfo *restrictinfo = castNode(RestrictInfo, lfirst(hcl));
+			RestrictInfo *restrictinfo = lfirst_node(RestrictInfo, hcl);
 			Selectivity thisbucketsize;
 
 			/*
@@ -3760,7 +3760,7 @@ compute_semi_anti_join_factors(PlannerInfo *root,
 		joinquals = NIL;
 		foreach(l, restrictlist)
 		{
-			RestrictInfo *rinfo = castNode(RestrictInfo, lfirst(l));
+			RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
 
 			if (!rinfo->is_pushed_down)
 				joinquals = lappend(joinquals, rinfo);
@@ -4192,7 +4192,7 @@ calc_joinrel_size_estimate(PlannerInfo *root,
 		/* Grovel through the clauses to separate into two lists */
 		foreach(l, restrictlist)
 		{
-			RestrictInfo *rinfo = castNode(RestrictInfo, lfirst(l));
+			RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
 
 			if (rinfo->is_pushed_down)
 				pushedquals = lappend(pushedquals, rinfo);
@@ -4568,7 +4568,7 @@ set_subquery_size_estimates(PlannerInfo *root, RelOptInfo *rel)
 	 */
 	foreach(lc, subroot->parse->targetList)
 	{
-		TargetEntry *te = castNode(TargetEntry, lfirst(lc));
+		TargetEntry *te = lfirst_node(TargetEntry, lc);
 		Node	   *texpr = (Node *) te->expr;
 		int32		item_width = 0;
 
diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index cec9822cb79..6e4bae854a3 100644
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -1277,7 +1277,7 @@ generate_bitmap_or_paths(PlannerInfo *root, RelOptInfo *rel,
 
 	foreach(lc, clauses)
 	{
-		RestrictInfo *rinfo = castNode(RestrictInfo, lfirst(lc));
+		RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
 		List	   *pathlist;
 		Path	   *bitmapqual;
 		ListCell   *j;
@@ -2188,7 +2188,7 @@ match_clauses_to_index(IndexOptInfo *index,
 
 	foreach(lc, clauses)
 	{
-		RestrictInfo *rinfo = castNode(RestrictInfo, lfirst(lc));
+		RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
 
 		match_clause_to_index(index, rinfo, clauseset);
 	}
diff --git a/src/backend/optimizer/path/joinrels.c b/src/backend/optimizer/path/joinrels.c
index 6a0c67b9abb..5a68de3cc86 100644
--- a/src/backend/optimizer/path/joinrels.c
+++ b/src/backend/optimizer/path/joinrels.c
@@ -1250,7 +1250,7 @@ restriction_is_constant_false(List *restrictlist, bool only_pushed_down)
 	 */
 	foreach(lc, restrictlist)
 	{
-		RestrictInfo *rinfo = castNode(RestrictInfo, lfirst(lc));
+		RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
 
 		if (only_pushed_down && !rinfo->is_pushed_down)
 			continue;