From 8aaf7bca34092bd958bc735cbe5cda6cad322f2b Mon Sep 17 00:00:00 2001
From: Mehmet Yilmaz <mehmetyilmaz@microsoft.com>
Date: Thu, 8 May 2025 15:46:04 +0000
Subject: [PATCH] =?UTF-8?q?Support=20PostgreSQL=2018=E2=80=99s=20new=20RTE?=
 =?UTF-8?q?=20kinds=20in=20Citus=20deparser=20to=20fix=20OID=200?=
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Enhance set_relation_column_names to handle relid validation and support for synthetic PG 18 RTEs

Handle unnamed groups in set_rtable_names by using the group's name
---
 citus-tools                                   |  1 +
 .../distributed/deparser/ruleutils_18.c       | 32 +++++++++++++++++--
 2 files changed, 31 insertions(+), 2 deletions(-)
 create mode 160000 citus-tools

diff --git a/citus-tools b/citus-tools
new file mode 160000
index 000000000..3376bd684
--- /dev/null
+++ b/citus-tools
@@ -0,0 +1 @@
+Subproject commit 3376bd6845f0614908ed304f5033bd644c82d3bf
diff --git a/src/backend/distributed/deparser/ruleutils_18.c b/src/backend/distributed/deparser/ruleutils_18.c
index 31d78b122..29a45c828 100644
--- a/src/backend/distributed/deparser/ruleutils_18.c
+++ b/src/backend/distributed/deparser/ruleutils_18.c
@@ -795,6 +795,11 @@ set_rtable_names(deparse_namespace *dpns, List *parent_namespaces,
 			/* Unnamed join has no refname */
 			refname = NULL;
 		}
+		else if (rte->rtekind == RTE_GROUP)
+		{
+			/* Use the name of the group */
+			refname = NULL;
+		}
 		else
 		{
 			/* Otherwise use whatever the parser assigned */
@@ -1191,8 +1196,9 @@ set_relation_column_names(deparse_namespace *dpns, RangeTblEntry *rte,
 	 * real_colnames[] will be indexed by physical column number, with NULL
 	 * entries for dropped columns.
 	 */
-	if (rte->rtekind == RTE_RELATION ||
-        GetRangeTblKind(rte) == CITUS_RTE_SHARD)
+	if ((rte->rtekind == RTE_RELATION ||
+		GetRangeTblKind(rte) == CITUS_RTE_SHARD) &&
+		OidIsValid(rte->relid))
 	{
 		/* Relation --- look to the system catalogs for up-to-date info */
 		Relation	rel;
@@ -1215,6 +1221,28 @@ set_relation_column_names(deparse_namespace *dpns, RangeTblEntry *rte,
 		}
 		relation_close(rel, AccessShareLock);
 	}
+	else if (GetRangeTblKind(rte) == CITUS_RTE_SHARD)
+	{
+		/* shard RTE without relid (pulled-up clone in PG18)            */
+		/* use the column aliases already stored in rte->eref->colnames */
+
+		ncolumns      = list_length(rte->eref->colnames);
+		real_colnames = (char **) palloc0(ncolumns * sizeof(char *));
+
+		for (i = 0; i < ncolumns; i++)
+			real_colnames[i] = pstrdup(strVal(list_nth(rte->eref->colnames, i)));
+
+		/* keep changed_any / has_anonymous defaults */
+	}
+    else if (rte->rtekind == RTE_GROUP)
+    {
+        /* ----- synthetic PG 18 RTE for GROUP BY / HAVING ----- */
+        ncolumns      = list_length(rte->eref->colnames);
+        real_colnames = (char **) palloc0(ncolumns * sizeof(char *));
+
+        for (i = 0; i < ncolumns; i++)
+            real_colnames[i] = pstrdup(strVal(list_nth(rte->eref->colnames, i)));
+    }	
 	else
 	{
 		/* Otherwise get the column names from eref or expandRTE() */