Add expression tree walkers for cypher nodes

- Added cypher_raw_expr_tree_walker and cypher_expr_tree_walker, based
  on Postgres's raw_expression_tree_walker and expression_tree_walker.
  These follow the same walker API as Postgres and add support for
  Cypher-specific nodes.
- Also added the agtype[] to agtype func and typecast to 1.5.0-y.y.y.sql
- Simplifies logic for cypher_subquery handling in where clause.
- Fixes a crash when list comprehension in the WHERE clause references a
  variable from the preceding MATCH clause.

Author: MuhammadTahaNaveed

age--1.5.0--y.y.y.sql

@@ -137,4 +137,15 @@ PARALLEL SAFE
 AS 'MODULE_PATHNAME';
 
 CREATE CAST (agtype AS json)
-    WITH FUNCTION ag_catalog.agtype_to_json(agtype);
+    WITH FUNCTION ag_catalog.agtype_to_json(agtype);
+
+CREATE FUNCTION ag_catalog.agtype_array_to_agtype(agtype[])
+    RETURNS agtype
+    LANGUAGE c
+    IMMUTABLE
+RETURNS NULL ON NULL INPUT
+PARALLEL SAFE
+AS 'MODULE_PATHNAME';
+
+CREATE CAST (agtype[] AS agtype)
+    WITH FUNCTION ag_catalog.agtype_array_to_agtype(agtype[]);

regress/expected/list_comprehension.out

@@ -707,6 +707,18 @@ SELECT * FROM cypher('list_comprehension', $$ MATCH (u {list: [0, 2, 4, 6, 8, 10
 ERROR:  Invalid use of aggregation in this context
 LINE 1: ... $$ MATCH (u {list: [0, 2, 4, 6, 8, 10, 12]}) SET u.c = coll...
                                                              ^
+SELECT * FROM cypher('list_comprehension', $$ MATCH (u {list: [0, 2, 4, 6, 8, 10, 12]}) WHERE u.list = [u IN [1, u]] RETURN u $$) AS (u agtype);
+ u 
+---
+(0 rows)
+
+SELECT * FROM cypher('list_comprehension', $$ MATCH (u {list: [0, 2, 4, 6, 8, 10, 12]}) WHERE u.list IN [u IN [1, u.list]] RETURN u $$) AS (u agtype);
+                                                                               u                                                                               
+---------------------------------------------------------------------------------------------------------------------------------------------------------------
+ {"id": 281474976710657, "label": "", "properties": {"a": [], "b": [0, 1, 2, 3, 4, 5], "c": [0, 2, 4, 6, 8, 10, 12], "list": [0, 2, 4, 6, 8, 10, 12]}}::vertex
+ {"id": 281474976710668, "label": "", "properties": {"b": [0, 1, 2, 3, 4, 5], "c": [0, 2, 4, 6, 8, 10, 12], "list": [0, 2, 4, 6, 8, 10, 12]}}::vertex
+(2 rows)
+
 -- Clean up
 SELECT * FROM drop_graph('list_comprehension', true);
 NOTICE:  drop cascades to 4 other objects

regress/sql/list_comprehension.sql

@@ -171,6 +171,8 @@ SELECT * FROM cypher('list_comprehension', $$ CREATE (u {list: [0, 2, 4, 6, 8, 1
 SELECT * FROM cypher('list_comprehension', $$ WITH [1, 2, 3] AS u UNWIND collect(u) AS v RETURN v $$) AS (result agtype);
 SELECT * FROM cypher('list_comprehension', $$ MATCH (u {list: [0, 2, 4, 6, 8, 10, 12]}) WITH u, collect(u.list) AS v SET u += {b: [u IN range(0, 5)]} SET u.c = [u IN v[0]] RETURN u $$) AS (result agtype);
 SELECT * FROM cypher('list_comprehension', $$ MATCH (u {list: [0, 2, 4, 6, 8, 10, 12]}) SET u.c = collect(u.list) RETURN u $$) AS (u agtype);
+SELECT * FROM cypher('list_comprehension', $$ MATCH (u {list: [0, 2, 4, 6, 8, 10, 12]}) WHERE u.list = [u IN [1, u]] RETURN u $$) AS (u agtype);
+SELECT * FROM cypher('list_comprehension', $$ MATCH (u {list: [0, 2, 4, 6, 8, 10, 12]}) WHERE u.list IN [u IN [1, u.list]] RETURN u $$) AS (u agtype);
 
 -- Clean up
 SELECT * FROM drop_graph('list_comprehension', true);

src/backend/nodes/cypher_outfuncs.c

@@ -117,7 +117,6 @@ void out_cypher_with(StringInfo str, const ExtensibleNode *node)
     DEFINE_AG_NODE(cypher_with);
 
     WRITE_BOOL_FIELD(distinct);
-    WRITE_BOOL_FIELD(subquery_intermediate);
     WRITE_NODE_FIELD(items);
     WRITE_NODE_FIELD(order_by);
     WRITE_NODE_FIELD(skip);

src/backend/optimizer/cypher_pathnode.c

@@ -23,13 +23,14 @@
 
 #include "optimizer/cypher_createplan.h"
 #include "optimizer/cypher_pathnode.h"
+#include "parser/cypher_analyze.h"
 #include "executor/cypher_utils.h"
 #include "optimizer/subselect.h"
 #include "nodes/makefuncs.h"
 
 static Const *convert_sublink_to_subplan(PlannerInfo *root,
                                          List *custom_private);
-static bool has_sublink(Node *node);
+static bool expr_has_sublink(Node *node, void *context);
 
 const CustomPathMethods cypher_create_path_methods = {
     CREATE_PATH_NAME, plan_cypher_create_path, NULL};
@@ -236,12 +237,10 @@ static Const *convert_sublink_to_subplan(PlannerInfo *root, List *custom_private
     {
         cypher_target_node *node = (cypher_target_node *)lfirst(lc);
         Node *prop_expr = (Node *) node->prop_expr;
-        if (prop_expr != NULL)
+
+        if (expr_has_sublink(prop_expr, NULL))
         {
-            if (has_sublink(prop_expr))
-            {
-                node->prop_expr = (Expr *) SS_process_sublinks(root, prop_expr, false);
-            }
+            node->prop_expr = (Expr *) SS_process_sublinks(root, prop_expr, false);
         }
     }
 
@@ -252,26 +251,20 @@ static Const *convert_sublink_to_subplan(PlannerInfo *root, List *custom_private
                      PointerGetDatum(str->data), false, false);
 }
 
-/* Helper function to check if the node is SubLink or has it embedded */
-static bool has_sublink(Node *node)
+/*
+ * Helper function to check if the node has a sublink.
+ */
+static bool expr_has_sublink(Node *node, void *context)
 {
     if (node == NULL)
+    {
         return false;
+    }
 
     if (IsA(node, SubLink))
-        return true;
-
-    if (IsA(node, FuncExpr))
     {
-        FuncExpr *fe = (FuncExpr *) node;
-        ListCell *lc;
-
-        foreach(lc, fe->args)
-        {
-            if (has_sublink((Node *) lfirst(lc)))
-                return true;
-        }
+        return true;
     }
 
-    return false;
+    return cypher_expr_tree_walker(node, expr_has_sublink, context);
 }