v20260415-0001-Collation-of-expressions-in-GRAPH_TABLE-CO.patch

From 7481f0d29508fc656efdd5ff2a692eeea406ac7a Mon Sep 17 00:00:00 2001
From: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Date: Wed, 15 Apr 2026 16:18:37 +0530
Subject: [PATCH v20260415 1/3] Collation of expressions in GRAPH_TABLE COLUMNS
 clause

GRAPH_TABLE clause is converted into a rangetable entry which is ignored
by assign_query_collations(). Hence we assign collations while
transforming its parts. Expressions in COLUMNS clause missed that
treatment.

While at also add comments about collation assignment to the parts of
GRAPH_TABLE clause and also fix a small grammar issue.

Reported-by: Satyanarayana Narlapuram <satyanarlapuram@gmail.com>
Author: Satyanarayana Narlapuram <satyanarlapuram@gmail.com>
Author: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Discussion: https://www.postgresql.org/message-id/CAHg+QDc4aaiufYSgrwMMPMMRTPtQ66SghcrPFbWJFZMqNaG+BA@mail.gmail.com
---
 src/backend/parser/parse_clause.c         |  6 ++++++
 src/backend/parser/parse_graphtable.c     | 12 +++++++++++-
 src/test/regress/expected/graph_table.out |  8 ++++----
 src/test/regress/sql/graph_table.sql      |  4 ++--
 4 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 967eea44f1c..4270c2382c4 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -1003,6 +1003,12 @@ transformRangeGraphTable(ParseState *pstate, RangeGraphTable *rgt)
 		columns = lappend(columns, te);
 	}
 
+	/*
+	 * Assign collations to column expressions now since
+	 * assign_query_collations() does not process rangetable entries.
+	 */
+	assign_list_collations(pstate, columns);
+
 	table_close(rel, NoLock);
 
 	pstate->p_graph_table_pstate = NULL;
diff --git a/src/backend/parser/parse_graphtable.c b/src/backend/parser/parse_graphtable.c
index 30ddce5aa9f..87386859a5c 100644
--- a/src/backend/parser/parse_graphtable.c
+++ b/src/backend/parser/parse_graphtable.c
@@ -252,6 +252,11 @@ transformGraphElementPattern(ParseState *pstate, GraphElementPattern *gep)
 	gep->labelexpr = transformLabelExpr(gpstate, gep->labelexpr);
 
 	gep->whereClause = transformExpr(pstate, gep->whereClause, EXPR_KIND_WHERE);
+
+	/*
+	 * Assign collations here for the reason mentioned in the prologue of
+	 * transformGraphPattern().
+	 */
 	assign_expr_collations(pstate, gep->whereClause);
 
 	gpstate->cur_gep = NULL;
@@ -366,9 +371,14 @@ transformPathPatternList(ParseState *pstate, List *path_pattern)
  * Transform a GraphPattern.
  *
  * A GraphPattern consists of a list of one or more path patterns and an
- * optional where clause. Transform them. We use the previously constructure
+ * optional where clause. Transform them. We use the previously constructed
  * list of variables in the GraphTableParseState to resolve property references
  * in the WHERE clause.
+ *
+ * Since most parts of the GraphPattern do not require collation assignment, we
+ * assign collations to the required expressions as they are transformed.  This
+ * avoids the need to traverse the whole GraphPattern again and avoids exposing
+ * it to assign_expr_collations().
  */
 Node *
 transformGraphPattern(ParseState *pstate, GraphPattern *graph_pattern)
diff --git a/src/test/regress/expected/graph_table.out b/src/test/regress/expected/graph_table.out
index b579e3df635..057f283c43d 100644
--- a/src/test/regress/expected/graph_table.out
+++ b/src/test/regress/expected/graph_table.out
@@ -652,13 +652,13 @@ SELECT * FROM GRAPH_TABLE (g1 MATCH (a)-(a) COLUMNS (a.vname AS self));
  v33
 (1 row)
 
--- test collation specified in the expression
+-- test explicit and implicit collation assignment
 INSERT INTO e3_3 VALUES (2003, 2003, 'E331', 10011);
-SELECT * FROM GRAPH_TABLE (g1 MATCH (a)-[b]->(a)-[b]->(a) COLUMNS (a.vname AS self, b.ename AS loop_name)) ORDER BY loop_name COLLATE "C" ASC;
+SELECT * FROM GRAPH_TABLE (g1 MATCH (a)-[b]->(a)-[b]->(a) COLUMNS (upper(a.vname) AS self, b.ename AS loop_name)) ORDER BY loop_name COLLATE "C" ASC;
  self | loop_name 
 ------+-----------
- v33  | E331
- v33  | e331
+ V33  | E331
+ V33  | e331
 (2 rows)
 
 SELECT * FROM GRAPH_TABLE (g1 MATCH (a)-[b IS el2 WHERE b.ename > 'E331' COLLATE "C"]->(a)-[b]->(a) COLUMNS (a.vname AS self, b.ename AS loop_name));
diff --git a/src/test/regress/sql/graph_table.sql b/src/test/regress/sql/graph_table.sql
index 4ff98817420..278064818ff 100644
--- a/src/test/regress/sql/graph_table.sql
+++ b/src/test/regress/sql/graph_table.sql
@@ -394,9 +394,9 @@ SELECT * FROM GRAPH_TABLE (g1 MATCH (a)-[b]->(c)-[b]->(d) COLUMNS (a.vname AS an
 SELECT * FROM GRAPH_TABLE (g1 MATCH (a)-[c]-(a) COLUMNS (a.vname AS self, c.ename AS loop_name));
 SELECT * FROM GRAPH_TABLE (g1 MATCH (a)-(a) COLUMNS (a.vname AS self));
 
--- test collation specified in the expression
+-- test explicit and implicit collation assignment
 INSERT INTO e3_3 VALUES (2003, 2003, 'E331', 10011);
-SELECT * FROM GRAPH_TABLE (g1 MATCH (a)-[b]->(a)-[b]->(a) COLUMNS (a.vname AS self, b.ename AS loop_name)) ORDER BY loop_name COLLATE "C" ASC;
+SELECT * FROM GRAPH_TABLE (g1 MATCH (a)-[b]->(a)-[b]->(a) COLUMNS (upper(a.vname) AS self, b.ename AS loop_name)) ORDER BY loop_name COLLATE "C" ASC;
 SELECT * FROM GRAPH_TABLE (g1 MATCH (a)-[b IS el2 WHERE b.ename > 'E331' COLLATE "C"]->(a)-[b]->(a) COLUMNS (a.vname AS self, b.ename AS loop_name));
 SELECT * FROM GRAPH_TABLE (g1 MATCH (a)-[b]->(a)-[b]->(a) WHERE b.ename > 'E331' COLLATE "C" COLUMNS (a.vname AS self, b.ename AS loop_name));
 SELECT * FROM GRAPH_TABLE (g1 MATCH (a)-[b]->(a)-[b]->(a) COLUMNS (a.vname AS self, b.ename AS loop_name)) WHERE loop_name > 'E331' COLLATE "C";

base-commit: f30d0c720f2ec979ab1b5b44b1f9f201d6efdf8c
-- 
2.34.1