fix: Remove cypher read clause restriction.

src/backend/parser/analyze.c

@@ -3496,28 +3496,19 @@ transformCypherStmt(ParseState *pstate, CypherStmt *stmt)
 				{
 					update_type = T_CypherCreateClause;
 				}
-				if (read)
-					ereport(ERROR,
-							(errcode(ERRCODE_SYNTAX_ERROR),
-							 errmsg("Cypher read clauses cannot follow update clauses")));
+				/* todo: restriction is required? */
 				break;
 			case T_CypherDeleteClause:
 			case T_CypherSetClause:
-				if (read)
-					ereport(ERROR,
-							(errcode(ERRCODE_SYNTAX_ERROR),
-							 errmsg("Cypher read clauses cannot follow update clauses")));
+				/* todo: restriction is required? */
 				break;
 			case T_CypherMergeClause:
 				if (update_type == T_Invalid ||
 					update_type == T_CypherCreateClause)
 				{
 					update_type = T_CypherMergeClause;
 				}
-				if (read)
-					ereport(ERROR,
-							(errcode(ERRCODE_SYNTAX_ERROR),
-							 errmsg("Cypher read clauses cannot follow update clauses")));
+				/* todo: restriction is required? */
 				break;
 			case T_CypherLoadClause:
 				read = true;

src/test/regress/expected/cypher_dml.out

@@ -2670,7 +2670,10 @@ MATCH (a) DETACH DELETE a;
 -- wrong case
 MERGE (a:v1) MERGE (b:v2 {name: a.notexistent});
 MERGE (a:v1) MATCH (b:v2 {name: a.name}) RETURN a, b;
-ERROR:  Cypher read clauses cannot follow update clauses
+ a | b 
+---+---
+(0 rows)
+
 MERGE (a:v1) MERGE (b:v2 {name: a.name}) MERGE (a);
 ERROR:  duplicate variable "a"
 LINE 1: MERGE (a:v1) MERGE (b:v2 {name: a.name}) MERGE (a);

src/test/regress/expected/cypher_eager.out

@@ -520,7 +520,10 @@ MATCH (a) RETURN properties(a);
 -- wrong case
 MERGE (a:v1) MERGE (b:v2 {name: a.notexistent});
 MERGE (a:v1) MATCH (b:v2 {name: a.name}) RETURN a, b;
-ERROR:  Cypher read clauses cannot follow update clauses
+ a | b 
+---+---
+(0 rows)
+
 MERGE (a:v1) MERGE (b:v2 {name: a.name}) MERGE (a);
 ERROR:  duplicate variable "a"
 LINE 1: MERGE (a:v1) MERGE (b:v2 {name: a.name}) MERGE (a);

src/test/regress/sql/cypher_dml2.sql

@@ -110,6 +110,29 @@ SELECT * FROM _trigger_history;
 
 DROP GRAPH cypher_dml2 CASCADE;
 
+-- #589 ( Cypher read clauses cannot follow update clauses )
+CREATE GRAPH cypher_dml2;
+SET GRAPH_PATH to cypher_dml2;
+
+CREATE VLABEL main;
+CREATE ELABEL main2;
+
+CREATE (n:another {id: 593}) RETURN n.id;
+
+MERGE (n:main {id: 593})
+ON CREATE SET n.id = 593
+WITH n
+MATCH (g: another)
+WHERE g.id = 593
+MERGE (g)-[:main2]->(n);
+
+MATCH ()-[e:main2]-() RETURN e;
+MATCH (g: another) RETURN g;
+MATCH (g: main) RETURN g;
+
+DROP GRAPH cypher_dml2 CASCADE;
+
+-- fix: Includes necessary JOINs of vertices (#599)
 CREATE GRAPH cypher_dml2;
 SET GRAPH_PATH to cypher_dml2;
 
@@ -130,4 +153,4 @@ EXPLAIN VERBOSE MATCH (a)-[]-(a) RETURN a;
 EXPLAIN VERBOSE MATCH (a)-[]-(a) RETURN *;
 EXPLAIN VERBOSE MATCH p=(a)-[]-(a) RETURN *;
 
-DROP GRAPH cypher_dml2 CASCADE;
+DROP GRAPH cypher_dml2 CASCADE;