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, 11 insertions, 11 deletions

diff --git a/src/backend/utils/cache/plancache.c b/src/backend/utils/cache/plancache.c
index 50da116cf4..abff7474f5 100644
--- a/src/backend/utils/cache/plancache.c
+++ b/src/backend/utils/cache/plancache.c
@@ -979,7 +979,7 @@ BuildCachedPlan(CachedPlanSource *plansource, List *qlist,
 	is_transient = false;
 	foreach(lc, plist)
 	{
-		PlannedStmt *plannedstmt = castNode(PlannedStmt, lfirst(lc));
+		PlannedStmt *plannedstmt = lfirst_node(PlannedStmt, lc);
 
 		if (plannedstmt->commandType == CMD_UTILITY)
 			continue;			/* Ignore utility statements */
@@ -1074,7 +1074,7 @@ cached_plan_cost(CachedPlan *plan, bool include_planner)
 
 	foreach(lc, plan->stmt_list)
 	{
-		PlannedStmt *plannedstmt = castNode(PlannedStmt, lfirst(lc));
+		PlannedStmt *plannedstmt = lfirst_node(PlannedStmt, lc);
 
 		if (plannedstmt->commandType == CMD_UTILITY)
 			continue;			/* Ignore utility statements */
@@ -1462,7 +1462,7 @@ QueryListGetPrimaryStmt(List *stmts)
 
 	foreach(lc, stmts)
 	{
-		Query	   *stmt = castNode(Query, lfirst(lc));
+		Query	   *stmt = lfirst_node(Query, lc);
 
 		if (stmt->canSetTag)
 			return stmt;
@@ -1481,7 +1481,7 @@ AcquireExecutorLocks(List *stmt_list, bool acquire)
 
 	foreach(lc1, stmt_list)
 	{
-		PlannedStmt *plannedstmt = castNode(PlannedStmt, lfirst(lc1));
+		PlannedStmt *plannedstmt = lfirst_node(PlannedStmt, lc1);
 		int			rt_index;
 		ListCell   *lc2;
 
@@ -1551,7 +1551,7 @@ AcquirePlannerLocks(List *stmt_list, bool acquire)
 
 	foreach(lc, stmt_list)
 	{
-		Query	   *query = castNode(Query, lfirst(lc));
+		Query	   *query = lfirst_node(Query, lc);
 
 		if (query->commandType == CMD_UTILITY)
 		{
@@ -1618,7 +1618,7 @@ ScanQueryForLocks(Query *parsetree, bool acquire)
 	/* Recurse into subquery-in-WITH */
 	foreach(lc, parsetree->cteList)
 	{
-		CommonTableExpr *cte = castNode(CommonTableExpr, lfirst(lc));
+		CommonTableExpr *cte = lfirst_node(CommonTableExpr, lc);
 
 		ScanQueryForLocks(castNode(Query, cte->ctequery), acquire);
 	}
@@ -1676,7 +1676,7 @@ PlanCacheComputeResultDesc(List *stmt_list)
 	{
 		case PORTAL_ONE_SELECT:
 		case PORTAL_ONE_MOD_WITH:
-			query = castNode(Query, linitial(stmt_list));
+			query = linitial_node(Query, stmt_list);
 			return ExecCleanTypeFromTL(query->targetList, false);
 
 		case PORTAL_ONE_RETURNING:
@@ -1685,7 +1685,7 @@ PlanCacheComputeResultDesc(List *stmt_list)
 			return ExecCleanTypeFromTL(query->returningList, false);
 
 		case PORTAL_UTIL_SELECT:
-			query = castNode(Query, linitial(stmt_list));
+			query = linitial_node(Query, stmt_list);
 			Assert(query->utilityStmt);
 			return UtilityTupleDescriptor(query->utilityStmt);
 
@@ -1742,7 +1742,7 @@ PlanCacheRelCallback(Datum arg, Oid relid)
 
 			foreach(lc, plansource->gplan->stmt_list)
 			{
-				PlannedStmt *plannedstmt = castNode(PlannedStmt, lfirst(lc));
+				PlannedStmt *plannedstmt = lfirst_node(PlannedStmt, lc);
 
 				if (plannedstmt->commandType == CMD_UTILITY)
 					continue;	/* Ignore utility statements */
@@ -1815,7 +1815,7 @@ PlanCacheFuncCallback(Datum arg, int cacheid, uint32 hashvalue)
 		{
 			foreach(lc, plansource->gplan->stmt_list)
 			{
-				PlannedStmt *plannedstmt = castNode(PlannedStmt, lfirst(lc));
+				PlannedStmt *plannedstmt = lfirst_node(PlannedStmt, lc);
 				ListCell   *lc3;
 
 				if (plannedstmt->commandType == CMD_UTILITY)
@@ -1888,7 +1888,7 @@ ResetPlanCache(void)
 		 */
 		foreach(lc, plansource->query_list)
 		{
-			Query	   *query = castNode(Query, lfirst(lc));
+			Query	   *query = lfirst_node(Query, lc);
 
 			if (query->commandType != CMD_UTILITY ||
 				UtilityContainsQuery(query->utilityStmt))