Fix MATCH after CREATE returning 0 rows (issue #2308)

regress/expected/cypher_match.out

@@ -3533,6 +3533,106 @@ SELECT * FROM cypher('test_enable_containment', $$ EXPLAIN (costs off) MATCH (x:
    Filter: ((agtype_access_operator(VARIADIC ARRAY[properties, '"school"'::agtype]) = '{"name": "XYZ College", "program": {"major": "Psyc", "degree": "BSc"}}'::agtype) AND (agtype_access_operator(VARIADIC ARRAY[properties, '"phone"'::agtype]) = '[123456789, 987654321, 456987123]'::agtype))
 (2 rows)
 
+--
+-- issue 2308: MATCH after CREATE returns 0 rows
+--
+-- When all MATCH variables are already bound from a preceding CREATE + WITH,
+-- the MATCH filter quals must evaluate after CREATE, not before.
+--
+SELECT create_graph('issue_2308');
+NOTICE:  graph "issue_2308" has been created
+ create_graph 
+--------------
+
+(1 row)
+
+-- Reporter's exact case: CREATE + WITH + MATCH + SET + RETURN
+SELECT * FROM cypher('issue_2308', $$
+    CREATE (a:TestB3)-[e:B3REL]->(b:TestB3)
+    WITH a, e, b
+    MATCH p = (a)-[e]->(b)
+    SET a.something = 'something'
+    RETURN a
+$$) AS (a agtype);
+                                              a                                               
+----------------------------------------------------------------------------------------------
+ {"id": 844424930131969, "label": "TestB3", "properties": {"something": "something"}}::vertex
+(1 row)
+
+-- Bound variables, no SET
+SELECT * FROM cypher('issue_2308', $$
+    CREATE (a:T2)-[e:R2]->(b:T2)
+    WITH a, e, b
+    MATCH (a)-[e]->(b)
+    RETURN a, e, b
+$$) AS (a agtype, e agtype, b agtype);
+                                 a                                 |                                                             e                                                             |                                 b                                 
+-------------------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------
+ {"id": 1407374883553281, "label": "T2", "properties": {}}::vertex | {"id": 1688849860263937, "label": "R2", "end_id": 1407374883553282, "start_id": 1407374883553281, "properties": {}}::edge | {"id": 1407374883553282, "label": "T2", "properties": {}}::vertex
+(1 row)
+
+-- Reversed direction: filter should reject (0 rows expected)
+SELECT * FROM cypher('issue_2308', $$
+    CREATE (a:T3)-[e:R3]->(b:T3)
+    WITH a, e, b
+    MATCH (b)-[e]->(a)
+    RETURN a
+$$) AS (a agtype);
+ a 
+---
+(0 rows)
+
+-- Node-only MATCH with bound variable
+SELECT * FROM cypher('issue_2308', $$
+    CREATE (a:T4 {name: 'test'})
+    WITH a
+    MATCH (a)
+    RETURN a
+$$) AS (a agtype);
+                                        a                                        
+---------------------------------------------------------------------------------
+ {"id": 2533274790395905, "label": "T4", "properties": {"name": "test"}}::vertex
+(1 row)
+
+-- MATCH after SET (SET is also DML, chain must be protected)
+SELECT * FROM cypher('issue_2308', $$
+    CREATE (a:T5 {val: 1})-[e:R5]->(b:T5 {val: 2})
+$$) AS (r agtype);
+ r 
+---
+(0 rows)
+
+SELECT * FROM cypher('issue_2308', $$
+    MATCH (a:T5)-[e:R5]->(b:T5)
+    SET a.val = 10
+    WITH a, e, b
+    MATCH (a)-[e]->(b)
+    RETURN a.val
+$$) AS (val agtype);
+ val 
+-----
+ 10
+(1 row)
+
+SELECT drop_graph('issue_2308', true);
+NOTICE:  drop cascades to 11 other objects
+DETAIL:  drop cascades to table issue_2308._ag_label_vertex
+drop cascades to table issue_2308._ag_label_edge
+drop cascades to table issue_2308."TestB3"
+drop cascades to table issue_2308."B3REL"
+drop cascades to table issue_2308."T2"
+drop cascades to table issue_2308."R2"
+drop cascades to table issue_2308."T3"
+drop cascades to table issue_2308."R3"
+drop cascades to table issue_2308."T4"
+drop cascades to table issue_2308."T5"
+drop cascades to table issue_2308."R5"
+NOTICE:  graph "issue_2308" has been dropped
+ drop_graph 
+------------
+
+(1 row)
+
 --
 -- Clean up
 --

regress/sql/cypher_match.sql

@@ -1437,6 +1437,61 @@ SELECT count(*) FROM cypher('test_enable_containment', $$ MATCH p=(x:Customer)-[
 SELECT * FROM cypher('test_enable_containment', $$ EXPLAIN (costs off) MATCH (x:Customer)-[:bought ={store: 'Amazon', addr:{city: 'Vancouver', street: 30}}]->(y:Product) RETURN 0 $$) as (a agtype);
 SELECT * FROM cypher('test_enable_containment', $$ EXPLAIN (costs off) MATCH (x:Customer ={school: { name: 'XYZ College',program: { major: 'Psyc', degree: 'BSc'} },phone: [ 123456789, 987654321, 456987123 ]}) RETURN 0 $$) as (a agtype);
 
+--
+-- issue 2308: MATCH after CREATE returns 0 rows
+--
+-- When all MATCH variables are already bound from a preceding CREATE + WITH,
+-- the MATCH filter quals must evaluate after CREATE, not before.
+--
+SELECT create_graph('issue_2308');
+
+-- Reporter's exact case: CREATE + WITH + MATCH + SET + RETURN
+SELECT * FROM cypher('issue_2308', $$
+    CREATE (a:TestB3)-[e:B3REL]->(b:TestB3)
+    WITH a, e, b
+    MATCH p = (a)-[e]->(b)
+    SET a.something = 'something'
+    RETURN a
+$$) AS (a agtype);
+
+-- Bound variables, no SET
+SELECT * FROM cypher('issue_2308', $$
+    CREATE (a:T2)-[e:R2]->(b:T2)
+    WITH a, e, b
+    MATCH (a)-[e]->(b)
+    RETURN a, e, b
+$$) AS (a agtype, e agtype, b agtype);
+
+-- Reversed direction: filter should reject (0 rows expected)
+SELECT * FROM cypher('issue_2308', $$
+    CREATE (a:T3)-[e:R3]->(b:T3)
+    WITH a, e, b
+    MATCH (b)-[e]->(a)
+    RETURN a
+$$) AS (a agtype);
+
+-- Node-only MATCH with bound variable
+SELECT * FROM cypher('issue_2308', $$
+    CREATE (a:T4 {name: 'test'})
+    WITH a
+    MATCH (a)
+    RETURN a
+$$) AS (a agtype);
+
+-- MATCH after SET (SET is also DML, chain must be protected)
+SELECT * FROM cypher('issue_2308', $$
+    CREATE (a:T5 {val: 1})-[e:R5]->(b:T5 {val: 2})
+$$) AS (r agtype);
+SELECT * FROM cypher('issue_2308', $$
+    MATCH (a:T5)-[e:R5]->(b:T5)
+    SET a.val = 10
+    WITH a, e, b
+    MATCH (a)-[e]->(b)
+    RETURN a.val
+$$) AS (val agtype);
+
+SELECT drop_graph('issue_2308', true);
+
 --
 -- Clean up
 --

src/backend/parser/cypher_clause.c

@@ -345,6 +345,7 @@ static bool isa_special_VLE_case(cypher_path *path);
 
 static ParseNamespaceItem *find_pnsi(cypher_parsestate *cpstate, char *varname);
 static bool has_list_comp_or_subquery(Node *expr, void *context);
+static bool clause_chain_has_dml(cypher_clause *clause);
 
 /*
  * Add required permissions to the RTEPermissionInfo for a relation.
@@ -2917,6 +2918,21 @@ static Query *transform_cypher_match_pattern(cypher_parsestate *cpstate,
 
             pnsi = transform_prev_cypher_clause(cpstate, clause->prev, true);
             rte = pnsi->p_rte;
+
+            /*
+             * If the predecessor clause chain contains a data-modifying
+             * operation (CREATE, SET, DELETE, MERGE), mark the subquery
+             * RTE as a security barrier. This prevents PostgreSQL's
+             * optimizer from pushing MATCH filter quals down into the
+             * subquery, which would cause them to evaluate before the
+             * DML executes -- resulting in quals checking NULL values
+             * and filtering out all rows.
+             */
+            if (clause_chain_has_dml(clause->prev))
+            {
+                rte->security_barrier = true;
+            }
+
             rtindex = list_length(pstate->p_rtable);
             /* rte is the first RangeTblEntry in pstate */
             if (rtindex != 1)
@@ -6545,6 +6561,28 @@ static void advance_transform_entities_to_next_clause(List *entities)
     }
 }
 
+/*
+ * Walk the clause chain and return true if any clause is a
+ * data-modifying operation (CREATE, SET, DELETE, or MERGE).
+ */
+static bool clause_chain_has_dml(cypher_clause *clause)
+{
+    while (clause != NULL)
+    {
+        if (is_ag_node(clause->self, cypher_create) ||
+            is_ag_node(clause->self, cypher_set) ||
+            is_ag_node(clause->self, cypher_delete) ||
+            is_ag_node(clause->self, cypher_merge))
+        {
+            return true;
+        }
+
+        clause = clause->prev;
+    }
+
+    return false;
+}
+
 static Query *analyze_cypher_clause(transform_method transform,
                                     cypher_clause *clause,
                                     cypher_parsestate *parent_cpstate)