Fix issue #1045 - error using path var in WHERE (#1295)

- Added cypher_path as an entity(along side cypher_node and
  cypher_relationship) in order for WHERE in MATCH clause to
  be able to reference it.

- Fixed relevant error messages to be more specific.

- Added regression tests.

regress/expected/cypher_match.out

@@ -2249,15 +2249,15 @@ ERROR:  variable "p" is for a path
 LINE 1: ...ELECT * FROM cypher('cypher_match', $$ MATCH p=()-[p]->() RE...
                                                              ^
 SELECT * FROM cypher('cypher_match', $$ MATCH p=() MATCH (p) RETURN p $$)as (p agtype);
-ERROR:  variable 'p' already exists
+ERROR:  variable 'p' is for a path
 LINE 1: ... FROM cypher('cypher_match', $$ MATCH p=() MATCH (p) RETURN ...
                                                              ^
 SELECT * FROM cypher('cypher_match', $$ MATCH p=() MATCH (p)-[]->() RETURN p $$)as (p agtype);
-ERROR:  variable 'p' already exists
+ERROR:  variable 'p' is for a path
 LINE 1: ... FROM cypher('cypher_match', $$ MATCH p=() MATCH (p)-[]->() ...
                                                              ^
 SELECT * FROM cypher('cypher_match', $$ MATCH p=() MATCH ()-[p]->() RETURN p $$)as (p agtype);
-ERROR:  variable 'p' already exists
+ERROR:  variable 'p' is for a path
 LINE 1: ...ROM cypher('cypher_match', $$ MATCH p=() MATCH ()-[p]->() RE...
                                                              ^
 SELECT * FROM cypher('cypher_match', $$ MATCH (p) MATCH p=() RETURN p $$)as (p agtype);
@@ -2784,6 +2784,51 @@ SELECT * FROM cypher('issue_945', $$ MATCH (a:Part) MATCH (b:Part) RETURN count(
  16
 (1 row)
 
+--
+-- Issue 1045
+--
+SELECT * FROM cypher('cypher_match', $$ MATCH p=()-[*]->() RETURN length(p) $$) as (length agtype);
+ length 
+--------
+ 1
+ 2
+ 1
+ 1
+ 1
+ 2
+ 1
+ 2
+(8 rows)
+
+SELECT * FROM cypher('cypher_match', $$ MATCH p=()-[*]->() WHERE length(p) > 1 RETURN length(p) $$) as (length agtype);
+ length 
+--------
+ 2
+ 2
+ 2
+(3 rows)
+
+SELECT * FROM cypher('cypher_match', $$ MATCH p=()-[*]->() WHERE size(nodes(p)) = 3 RETURN nodes(p)[0] $$) as (nodes agtype);
+                                                nodes                                                
+-----------------------------------------------------------------------------------------------------
+ {"id": 281474976710660, "label": "_ag_label_vertex", "properties": {"age": 4, "name": "F"}}::vertex
+ {"id": 281474976710667, "label": "_ag_label_vertex", "properties": {"name": "Dave"}}::vertex
+ {"id": 281474976710668, "label": "_ag_label_vertex", "properties": {"name": "John"}}::vertex
+(3 rows)
+
+SELECT * FROM cypher('cypher_match', $$ MATCH (n {name:'Dave'}) MATCH p=()-[*]->() WHERE nodes(p)[0] = n RETURN length(p) $$) as (length agtype);
+ length 
+--------
+ 1
+ 2
+(2 rows)
+
+SELECT * FROM cypher('cypher_match', $$ MATCH p1=(n {name:'Dave'})-[]->() MATCH p2=()-[*]->() WHERE p2=p1 RETURN p2=p1 $$) as (path agtype);
+ path 
+------
+ true
+(1 row)
+
 --
 -- Clean up
 --

regress/expected/cypher_vle.out

@@ -807,7 +807,7 @@ ERROR:  variable 'p' is for a VLE edge
 LINE 1: ... cypher('cypher_vle', $$ MATCH ()-[p *]-() MATCH (p) RETURN ...
                                                              ^
 SELECT * FROM cypher('cypher_vle', $$ MATCH p=() MATCH ()-[p *]-() RETURN p $$)as (p agtype);
-ERROR:  variable 'p' already exists
+ERROR:  variable 'p' is for a path
 LINE 1: ... FROM cypher('cypher_vle', $$ MATCH p=() MATCH ()-[p *]-() R...
                                                              ^
 SELECT * FROM cypher('cypher_vle', $$ MATCH ()-[p *]-() MATCH p=() RETURN p $$)as (p agtype);

regress/sql/cypher_match.sql

@@ -1169,6 +1169,15 @@ SELECT * FROM cypher('issue_945', $$ MATCH (:Part) MATCH (b:Part) RETURN count(*
 SELECT * FROM cypher('issue_945', $$ MATCH (a:Part) MATCH (b:Part) RETURN count(*) $$) as (result agtype);
 
 
+--
+-- Issue 1045
+--
+SELECT * FROM cypher('cypher_match', $$ MATCH p=()-[*]->() RETURN length(p) $$) as (length agtype);
+SELECT * FROM cypher('cypher_match', $$ MATCH p=()-[*]->() WHERE length(p) > 1 RETURN length(p) $$) as (length agtype);
+SELECT * FROM cypher('cypher_match', $$ MATCH p=()-[*]->() WHERE size(nodes(p)) = 3 RETURN nodes(p)[0] $$) as (nodes agtype);
+SELECT * FROM cypher('cypher_match', $$ MATCH (n {name:'Dave'}) MATCH p=()-[*]->() WHERE nodes(p)[0] = n RETURN length(p) $$) as (length agtype);
+SELECT * FROM cypher('cypher_match', $$ MATCH p1=(n {name:'Dave'})-[]->() MATCH p2=()-[*]->() WHERE p2=p1 RETURN p2=p1 $$) as (path agtype);
+
 --
 -- Clean up
 --

src/backend/parser/cypher_clause.c

@@ -3907,6 +3907,13 @@ static transform_entity *transform_VLE_edge_entity(cypher_parsestate *cpstate,
                         errmsg("variable '%s' is for an edge", rel->name),
                         parser_errposition(pstate, rel->location)));
             }
+            else if (entity->type == ENT_PATH)
+            {
+                ereport(ERROR,
+                       (errcode(ERRCODE_DUPLICATE_ALIAS),
+                        errmsg("variable '%s' is for a path", rel->name),
+                        parser_errposition(pstate, rel->location)));
+            }
             else
             {
                 ereport(ERROR,
@@ -4497,9 +4504,13 @@ transform_match_create_path_variable(cypher_parsestate *cpstate,
     /* otherwise, build the expr node for the function */
     else
     {
+        transform_entity *entity;
         expr = (Expr*)makeFuncExpr(build_path_oid, AGTYPEOID, entity_exprs,
                                    InvalidOid, InvalidOid,
                                    COERCE_EXPLICIT_CALL);
+
+        entity = make_transform_entity(cpstate, ENT_PATH, (Node *)path, expr);
+        cpstate->entities = lappend(cpstate->entities, entity);
     }
 
     resno = cpstate->pstate.p_next_resno++;
@@ -4668,6 +4679,13 @@ static Expr *transform_cypher_edge(cypher_parsestate *cpstate,
                         errmsg("variable '%s' is for a VLE edge", rel->name),
                         parser_errposition(pstate, rel->location)));
             }
+            else if (entity->type == ENT_PATH)
+            {
+                ereport(ERROR,
+                       (errcode(ERRCODE_DUPLICATE_ALIAS),
+                        errmsg("variable '%s' is for a path", rel->name),
+                        parser_errposition(pstate, rel->location)));
+            }
         }
 
         else if (te && !entity)
@@ -4907,6 +4925,13 @@ static Expr *transform_cypher_node(cypher_parsestate *cpstate,
                         errmsg("variable '%s' is for a VLE edge", node->name),
                         parser_errposition(pstate, node->location)));
             }
+            else if (entity->type == ENT_PATH)
+            {
+                ereport(ERROR,
+                       (errcode(ERRCODE_DUPLICATE_ALIAS),
+                        errmsg("variable '%s' is for a path", node->name),
+                        parser_errposition(pstate, node->location)));
+            }
         }
 
         /* If their is a te but no entity, it implies that their is

src/backend/parser/cypher_expr.c

@@ -341,17 +341,15 @@ static Node *transform_ColumnRef(cypher_parsestate *cpstate, ColumnRef *cref)
                 }
 
                 /*
-                 * If expr_kind is WHERE, Try to find the columnRef as a
-                 * transform_entity and extract the expr.
+                 * Try to find the columnRef as a transform_entity
+                 * and extract the expr.
                  */
-                if (pstate->p_expr_kind == EXPR_KIND_WHERE)
+                te = find_variable(cpstate, colname) ;
+                if (te != NULL && te->expr != NULL &&
+                    te->declared_in_current_clause)
                 {
-                    te = find_variable(cpstate, colname) ;
-                    if (te != NULL && te->expr != NULL)
-                    {
-                        node = (Node *)te->expr;
-                        break;
-                    }
+                    node = (Node *)te->expr;
+                    break;
                 }
                 /*
                  * Not known as a column of any range-table entry.

src/backend/parser/cypher_transform_entity.c

@@ -39,6 +39,10 @@ transform_entity *make_transform_entity(cypher_parsestate *cpstate,
     {
         entity->entity.rel = (cypher_relationship *)node;
     }
+    else if (entity->type == ENT_PATH)
+    {
+        entity->entity.path = (cypher_path *)node;
+    }
     else
     {
         ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -90,6 +94,13 @@ transform_entity *find_transform_entity(cypher_parsestate *cpstate,
                 return entity;
             }
         }
+        else if (type == ENT_PATH)
+        {
+            if (entity->entity.path->var_name != NULL && !strcmp(entity->entity.path->var_name, name))
+            {
+                return entity;
+            }
+        }
     }
 
     return NULL;
@@ -116,6 +127,10 @@ transform_entity *find_variable(cypher_parsestate *cpstate, char *name)
         {
             entity_name = entity->entity.rel->name;
         }
+        else if (entity->type == ENT_PATH)
+        {
+            entity_name = entity->entity.path->var_name;
+        }
         else
         {
             ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -142,6 +157,10 @@ char *get_entity_name(transform_entity *entity)
     {
         return entity->entity.node->name;
     }
+    else if (entity->type == ENT_PATH)
+    {
+        return entity->entity.path->var_name;
+    }
     else
     {
         ereport(ERROR,

src/include/parser/cypher_transform_entity.h

@@ -31,7 +31,8 @@ enum transform_entity_type
 {
     ENT_VERTEX = 0x0,
     ENT_EDGE,
-    ENT_VLE_EDGE
+    ENT_VLE_EDGE,
+    ENT_PATH
 };
 
 enum transform_entity_join_side
@@ -83,6 +84,7 @@ typedef struct
     {
         cypher_node *node;
         cypher_relationship *rel;
+        cypher_path *path;
     } entity;
 } transform_entity;