Refactor compatibility handling for PostgreSQL versions in various files

src/backend/columnar/columnar_metadata.c

@@ -1743,8 +1743,6 @@ create_estate_for_relation(Relation rel)
 #if PG_VERSION_NUM >= PG_VERSION_16
 	List *perminfos = NIL;
 	addRTEPermissionInfo(&perminfos, rte);
-#else
-	List *perminfos = NIL;  /* not used on PG 15 */
 #endif
 
 /* Initialize the range table, with the right signature for each PG version */

src/backend/distributed/deparser/ruleutils_18.c

@@ -1211,7 +1211,7 @@ set_relation_column_names(deparse_namespace *dpns, RangeTblEntry *rte,
 		if (rte->rtekind == RTE_FUNCTION && rte->functions != NIL)
 		{
 			/* Since we're not creating Vars, rtindex etc. don't matter */
-			expandRTE(rte, 1, 0, -1, true /* include dropped */ ,
+			expandRTE(rte, 1, 0, VAR_RETURNING_DEFAULT, -1, true /* include dropped */ ,
 					  &colnames, NULL);
 		}
 		else
@@ -4611,6 +4611,7 @@ get_name_for_var_field(Var *var, int fieldno,
 		case RTE_VALUES:
 		case RTE_NAMEDTUPLESTORE:
 		case RTE_RESULT:
+		case RTE_GROUP:
 
 			/*
 			 * This case should not occur: a column of a table or values list

src/backend/distributed/planner/multi_explain.c

@@ -2315,7 +2315,7 @@ ExplainWorkerPlan(PlannedStmt *plannedstmt, DestReceiver *dest, ExplainState *es
 	if (es->costs)
 		ExplainPrintJITSummary(es, queryDesc);
 
-#if PG_VERSION_NUM >= PG_VERSION_17 && PG_VERSION_NUM < PG_VERSION_1
+#if PG_VERSION_NUM >= PG_VERSION_17 && PG_VERSION_NUM < PG_VERSION_18
 	if (es->serialize != EXPLAIN_SERIALIZE_NONE)
 	{
 		/* the SERIALIZE option requires its own tuple receiver */

src/backend/distributed/test/fake_fdw.c

@@ -91,23 +91,11 @@ FakeGetForeignPaths(PlannerInfo *root, RelOptInfo *baserel, Oid foreigntableid)
 	Cost startup_cost = 0;
 	Cost total_cost = startup_cost + baserel->rows;
 
-	add_path(baserel,
-			 (Path *) create_foreignscan_path_compat(
-				 root,
-				 baserel,
-				 baserel->reltarget, /* ← PathTarget* is the rel’s reltarget */
-				 baserel->rows,
-				 0,              /* ← disabled_nodes (only used in PG18+) */
-				 startup_cost,
-				 total_cost,
-				 NIL,            /* pathkeys */
-				 NULL,           /* required_outer */
-				 NULL,           /* fdw_outerpath */
-				 NIL,            /* fdw_restrictinfo (PG18+) */
-				 NIL,            /* fdw_private */
-				 NIL             /* fdw_scan_tlist (PG15–17) */
-				 )
-			 );
+	add_path(baserel, (Path *) create_foreignscan_path_compat(root, baserel, NULL,
+															  baserel->rows,
+															  startup_cost, total_cost,
+															  NIL,
+															  NULL, NULL, NIL, NIL));
 }
 
 

src/include/pg_version_compat.h

@@ -384,70 +384,34 @@ getStxstattarget_compat(HeapTuple tup)
 
 #define matched_compat(a) (a->matchKind == MERGE_WHEN_MATCHED)
 
-#include "nodes/pg_list.h"       /* for List */
-#include "nodes/plannodes.h"     /* for ForeignScan */
-#include "optimizer/pathnode.h"  /* for create_foreignscan_path, ForeignPath */
+#include "nodes/bitmapset.h"      /* for Relids */
+#include "nodes/pg_list.h"        /* for List */
+#include "optimizer/pathnode.h"   /* for create_foreignscan_path() */
 
-/*
- * A single entry point for Citus code to build ForeignPath
- * using the *full* superset of parameters:
- *
- *   root, rel, target, rows,
- *   disabled_nodes, startup_cost, total_cost,
- *   pathkeys, required_outer,
- *   fdw_outerpath, fdw_restrictinfo,
- *   fdw_private, fdw_scan_tlist
- */
-static inline ForeignPath *
-create_foreignscan_path_compat(PlannerInfo *root,
-							   RelOptInfo *rel,
-							   PathTarget *target,
-							   double rows,
-							   int disabled_nodes,
-							   Cost startup_cost,
-							   Cost total_cost,
-							   List *pathkeys,
-							   Relids required_outer,
-							   Path *fdw_outerpath,
-							   List *fdw_restrictinfo,
-							   List *fdw_private,
-							   List *fdw_scan_tlist)
-{
 #if PG_VERSION_NUM >= PG_VERSION_18
-
-	/* PG 18+ signature: 12 args */
-	return create_foreignscan_path(
-		root,
-		rel,
-		target,
-		rows,
-		disabled_nodes,
-		startup_cost,
-		total_cost,
-		pathkeys,
-		required_outer,
-		fdw_outerpath,
-		fdw_restrictinfo,
-		fdw_private
-		);
+#define create_foreignscan_path_compat(a, b, c, d, e, f, g, h, i, j, k) \
+	create_foreignscan_path( \
+		(a),            /* root            */ \
+		(b),            /* rel             */ \
+		(c),            /* target          */ \
+		(d),            /* rows            */ \
+		0,              /* disabled_nodes  */ \
+		(e),            /* startup_cost    */ \
+		(f),            /* total_cost      */ \
+		(g),            /* pathkeys        */ \
+		(h),            /* required_outer  */ \
+		(i),            /* fdw_outerpath   */ \
+		(j),            /* fdw_restrictinfo*/ \
+		(k)             /* fdw_private     */ \
+		)
 #else
-
-	/* PG 17- signature: 11 args */
-	return create_foreignscan_path(
-		root,
-		rel,
-		target,
-		rows,
-		startup_cost,
-		total_cost,
-		pathkeys,
-		required_outer,
-		fdw_outerpath,
-		fdw_private,
-		fdw_scan_tlist
-		);
+#define create_foreignscan_path_compat(a, b, c, d, e, f, g, h, i, j, k) \
+	create_foreignscan_path( \
+		(a), (b), (c), (d), \
+		(e), (f), \
+		(g), (h), (i), (j), (k) \
+		)
 #endif
-}
 
 
 #define getProcNo_compat(a) (a->vxid.procNumber)
@@ -483,6 +447,10 @@ getStxstattarget_compat(HeapTuple tup)
 
 #define matched_compat(a) (a->matched)
 
+#define create_foreignscan_path_compat(a, b, c, d, e, f, g, h, i, j, \
+									   k) create_foreignscan_path(a, b, c, d, e, f, g, h, \
+																  i, k)
+
 #define getProcNo_compat(a) (a->pgprocno)
 #define getLxid_compat(a) (a->lxid)