Fix Issue 945 - incorrect count(*) return values

regress/expected/cypher_delete.out

@@ -707,8 +707,8 @@ SELECT * FROM cypher('detach_delete', $$ MATCH ()-[e]->() RETURN e.name $$) as (
 -------
  "ab"
  "cd"
- "nm"
  "am"
+ "nm"
  "pq"
 (5 rows)
 

regress/expected/cypher_set.out

@@ -167,8 +167,8 @@ SELECT * FROM cypher('cypher_set', $$MATCH ()-[n]->(:other_v) RETURN n$$) AS (a
 ----------------------------------------------------------------------------------------------------------------------------------------
  {"id": 1125899906842625, "label": "e", "end_id": 1407374883553281, "start_id": 281474976710657, "properties": {"i": 3, "j": 20}}::edge
  {"id": 1125899906842626, "label": "e", "end_id": 1407374883553282, "start_id": 844424930131969, "properties": {"i": 3, "j": 20}}::edge
- {"id": 1125899906842627, "label": "e", "end_id": 1407374883553283, "start_id": 844424930131971, "properties": {"i": 3, "j": 20}}::edge
  {"id": 1125899906842628, "label": "e", "end_id": 1407374883553284, "start_id": 844424930131970, "properties": {"i": 3, "j": 20}}::edge
+ {"id": 1125899906842627, "label": "e", "end_id": 1407374883553283, "start_id": 844424930131971, "properties": {"i": 3, "j": 20}}::edge
 (4 rows)
 
 SELECT * FROM cypher('cypher_set', $$

regress/expected/expr.out

@@ -2337,10 +2337,10 @@ SELECT * FROM cypher('expr', $$ MATCH (v) RETURN v $$) AS (expression agtype);
 SELECT * FROM cypher('expr', $$ MATCH ()-[e]-() RETURN e $$) AS (expression agtype);
                                                         expression                                                         
 ---------------------------------------------------------------------------------------------------------------------------
- {"id": 1407374883553282, "label": "e1", "end_id": 1125899906842626, "start_id": 1125899906842625, "properties": {}}::edge
  {"id": 1407374883553281, "label": "e1", "end_id": 1125899906842627, "start_id": 1125899906842626, "properties": {}}::edge
- {"id": 1407374883553282, "label": "e1", "end_id": 1125899906842626, "start_id": 1125899906842625, "properties": {}}::edge
  {"id": 1407374883553281, "label": "e1", "end_id": 1125899906842627, "start_id": 1125899906842626, "properties": {}}::edge
+ {"id": 1407374883553282, "label": "e1", "end_id": 1125899906842626, "start_id": 1125899906842625, "properties": {}}::edge
+ {"id": 1407374883553282, "label": "e1", "end_id": 1125899906842626, "start_id": 1125899906842625, "properties": {}}::edge
 (4 rows)
 
 -- id()
@@ -2349,10 +2349,10 @@ SELECT * FROM cypher('expr', $$
 $$) AS (id agtype);
         id        
 ------------------
- 1407374883553282
  1407374883553281
- 1407374883553282
  1407374883553281
+ 1407374883553282
+ 1407374883553282
 (4 rows)
 
 SELECT * FROM cypher('expr', $$
@@ -2391,10 +2391,10 @@ SELECT * FROM cypher('expr', $$
 $$) AS (start_id agtype);
      start_id     
 ------------------
- 1125899906842625
  1125899906842626
- 1125899906842625
  1125899906842626
+ 1125899906842625
+ 1125899906842625
 (4 rows)
 
 -- should return null
@@ -2424,10 +2424,10 @@ SELECT * FROM cypher('expr', $$
 $$) AS (end_id agtype);
       end_id      
 ------------------
- 1125899906842626
  1125899906842627
- 1125899906842626
  1125899906842627
+ 1125899906842626
+ 1125899906842626
 (4 rows)
 
 -- should return null

regress/sql/cypher_match.sql

@@ -1132,12 +1132,50 @@ SELECT count(*) FROM cypher('test_enable_containment', $$ MATCH (x:Customer {pho
 SELECT count(*) FROM cypher('test_enable_containment', $$ MATCH (x:Customer {phone:[654765876]}) RETURN x $$) as (a agtype);
 SELECT * FROM cypher('test_enable_containment', $$ EXPLAIN (COSTS OFF) MATCH (x:Customer {school:{name:'XYZ',program:{degree:'BSc'}},phone:[987654321],parents:{}}) RETURN x $$) as (a agtype);
 
+--
+-- Issue 945
+--
+SELECT create_graph('issue_945');
+SELECT * FROM cypher('issue_945', $$
+    CREATE (a:Part {part_num: '123'}),
+           (b:Part {part_num: '345'}),
+           (c:Part {part_num: '456'}),
+           (d:Part {part_num: '789'})
+    $$) as (result agtype);
+
+-- should match 4
+SELECT * FROM cypher('issue_945', $$
+    MATCH (a:Part) RETURN a
+    $$) as (result agtype);
+
+-- each should return 4
+SELECT * FROM cypher('issue_945', $$ MATCH (:Part) RETURN count(*) $$) as (result agtype);
+SELECT * FROM cypher('issue_945', $$ MATCH (a:Part) RETURN count(*) $$) as (result agtype);
+
+-- each should return 4 rows of 0
+SELECT * FROM cypher('issue_945', $$ MATCH (:Part) RETURN 0 $$) as (result agtype);
+SELECT * FROM cypher('issue_945', $$ MATCH (a:Part) RETURN 0 $$) as (result agtype);
+
+-- each should return 16 rows of 0
+SELECT * FROM cypher('issue_945', $$ MATCH (:Part) MATCH (:Part) RETURN 0 $$) as (result agtype);
+SELECT * FROM cypher('issue_945', $$ MATCH (a:Part) MATCH (:Part) RETURN 0 $$) as (result agtype);
+SELECT * FROM cypher('issue_945', $$ MATCH (:Part) MATCH (b:Part) RETURN 0 $$) as (result agtype);
+SELECT * FROM cypher('issue_945', $$ MATCH (a:Part) MATCH (b:Part) RETURN 0 $$) as (result agtype);
+
+-- each should return a count of 16
+SELECT * FROM cypher('issue_945', $$ MATCH (:Part) MATCH (:Part) RETURN count(*) $$) as (result agtype);
+SELECT * FROM cypher('issue_945', $$ MATCH (a:Part) MATCH (:Part) RETURN count(*) $$) as (result agtype);
+SELECT * FROM cypher('issue_945', $$ MATCH (:Part) MATCH (b:Part) RETURN count(*) $$) as (result agtype);
+SELECT * FROM cypher('issue_945', $$ MATCH (a:Part) MATCH (b:Part) RETURN count(*) $$) as (result agtype);
+
+
 --
 -- Clean up
 --
 SELECT drop_graph('cypher_match', true);
 SELECT drop_graph('test_retrieve_var', true);
 SELECT drop_graph('test_enable_containment', true);
+SELECT drop_graph('issue_945', true);
 
 --
 -- End

src/backend/parser/cypher_clause.c

@@ -4079,7 +4079,7 @@ static List *transform_match_entities(cypher_parsestate *cpstate, Query *query,
                                     node->name),
                             parser_errposition(pstate, node->location)));
                 }
-                
+
                 /*
                  * Checks the previous clauses to see if the variable already
                  * exists.
@@ -4096,6 +4096,22 @@ static List *transform_match_entities(cypher_parsestate *cpstate, Query *query,
             output_node = (special_VLE_case && !node->name && !node->props) ?
                           false :
                           INCLUDE_NODE_IN_JOIN_TREE(path, node);
+            /*
+             * TODO
+             *
+             * We need to re-evaluate if we want to use output_node or not.
+             * If output_node is set to false, then it basically short circuits
+             * the match for instances where a variable isn't specified. While,
+             * on the surface, this appears to be a good way to improve
+             * execution time of commands that won't do anything, it also
+             * causes chained commands to not work correctly. This is because
+             * a match without a variable will still feed its tuples to the next
+             * stage(s). With this set to false, it won't. So we likely need to
+             * remove all of the output_node logic. This needs to be reviewed,
+             * though. For now, we just set it to true and update the output of
+             * the regression tests.
+             */
+            output_node = true;
 
             /* transform vertex */
             expr = transform_cypher_node(cpstate, node, &query->targetList,