jihot2000 opened a new issue, #222:
URL: https://github.com/apache/incubator-age/issues/222
**Description**
I described a bug in issue #220. But it makes one confused because I cannot
prove that the logic of ```show_list_use_loop``` is the same as
```show_list_use_vle```.
So I rewrite my test case to make the question clear.
**How are you accessing AGE (Command line, driver, etc.)?**
run a sql file using psql command line
**the sql file 1**
```sql
CREATE SCHEMA test_vle;
SET search_path = test_vle, ag_catalog, "$user";
SELECT create_graph('mygraph');
SELECT create_vlabel('mygraph', 'head');
SELECT create_vlabel('mygraph', 'tail');
SELECT create_vlabel('mygraph', 'node');
SELECT create_elabel('mygraph', 'next');
SELECT * FROM cypher('mygraph', $CYPHER$
MERGE (:head {name: "list01"})-[:next]->(:tail {name: "list01"})
$CYPHER$) AS (a agtype);
SELECT * FROM cypher('mygraph', $CYPHER$
MATCH (h:head {name: "list01"})-[e:next]->(v)
DELETE e
CREATE (h)-[:next]->(:node {content: "a"})-[:next]->(v)
$CYPHER$) AS (a agtype);
SELECT * FROM cypher('mygraph', $CYPHER$
MATCH (h:head {name: 'list01'})-[:next*]->(v:node)
RETURN v
$CYPHER$) AS (node agtype);
SELECT * FROM cypher('mygraph', $CYPHER$
MATCH (h:head {name: "list01"})-[e:next]->(v)
DELETE e
CREATE (h)-[:next]->(:node {content: "b"})-[:next]->(v)
$CYPHER$) AS (a agtype);
SELECT * FROM cypher('mygraph', $CYPHER$
MATCH (h:head {name: 'list01'})-[:next*]->(v:node)
RETURN v
$CYPHER$) AS (node agtype);
SELECT * FROM cypher('mygraph', $CYPHER$
MATCH p=(:head)-[:next]->(:node)-[:next]->(:node)-[:next]->(:tail)
RETURN p
$CYPHER$) AS (path agtype);
SELECT drop_graph('mygraph', true);
DROP SCHEMA test_vle CASCADE;
```
Its output is
```
a
---
(0 rows)
a
---
(0 rows)
node
-----------------------------------------------------------------------------------
{"id": 1407374883553281, "label": "node", "properties": {"content":
"a"}}::vertex
(1 row)
a
---
(0 rows)
node
-----------------------------------------------------------------------------------
{"id": 1407374883553281, "label": "node", "properties": {"content":
"a"}}::vertex
{"id": 1407374883553282, "label": "node", "properties": {"content":
"b"}}::vertex
(2 rows)
path
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
[{"id": 844424930131969, "label": "head", "properties": {"name":
"list01"}}::vertex, {"id": 1688849860263941, "label": "next", "end_id":
1407374883553282, "start_id": 844424930131969, "properties": {}}::edge, {"id":
1407374883553282, "label": "node", "properties": {"content": "b"}}::vertex,
{"id": 1688849860263940, "label": "next", "end_id": 1407374883553281,
"start_id": 1407374883553282, "properties": {}}::edge, {"id": 1407374883553281,
"label": "node", "properties": {"content": "a"}}::vertex, {"id":
1688849860263938, "label": "next", "end_id": 1125899906842625, "start_id":
1407374883553281, "properties": {}}::edge, {"id": 1125899906842625, "label":
"tail", "properties": {"name": "list01"}}::vertex]::path
(1 row)
```
**the sql file 2**
```sql
CREATE SCHEMA test_vle;
SET search_path = test_vle, ag_catalog, "$user";
SELECT create_graph('mygraph');
SELECT create_vlabel('mygraph', 'head');
SELECT create_vlabel('mygraph', 'tail');
SELECT create_vlabel('mygraph', 'node');
SELECT create_elabel('mygraph', 'next');
CREATE OR REPLACE FUNCTION show_list_use_vle()
RETURNS TABLE(node agtype)
LANGUAGE 'plpgsql'
AS $$
DECLARE
BEGIN
RETURN QUERY
SELECT * FROM cypher('mygraph', $CYPHER$
MATCH (h:head {name: "list01"})-[:next*]->(v:node)
RETURN v
$CYPHER$) AS (node agtype);
END $$;
SELECT * FROM cypher('mygraph', $CYPHER$
MERGE (:head {name: "list01"})-[:next]->(:tail {name: "list01"})
$CYPHER$) AS (a agtype);
SELECT * FROM cypher('mygraph', $CYPHER$
MATCH (h:head {name: "list01"})-[e:next]->(v)
DELETE e
CREATE (h)-[:next]->(:node {content: "a"})-[:next]->(v)
$CYPHER$) AS (a agtype);
SELECT * FROM show_list_use_vle();
SELECT * FROM cypher('mygraph', $CYPHER$
MATCH (h:head {name: "list01"})-[e:next]->(v)
DELETE e
CREATE (h)-[:next]->(:node {content: "b"})-[:next]->(v)
$CYPHER$) AS (a agtype);
SELECT * FROM show_list_use_vle();
SELECT * FROM cypher('mygraph', $CYPHER$
MATCH p=(:head)-[:next]->(:node)-[:next]->(:node)-[:next]->(:tail)
RETURN p
$CYPHER$) AS (path agtype);
SELECT drop_graph('mygraph', true);
DROP SCHEMA test_vle CASCADE;
```
Its output is
```
a
---
(0 rows)
a
---
(0 rows)
node
-----------------------------------------------------------------------------------
{"id": 1407374883553281, "label": "node", "properties": {"content":
"a"}}::vertex
(1 row)
a
---
(0 rows)
node
-----------------------------------------------------------------------------------
{"id": 1407374883553281, "label": "node", "properties": {"content":
"a"}}::vertex
(1 row)
path
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
[{"id": 844424930131969, "label": "head", "properties": {"name":
"list01"}}::vertex, {"id": 1688849860263941, "label": "next", "end_id":
1407374883553282, "start_id": 844424930131969, "properties": {}}::edge, {"id":
1407374883553282, "label": "node", "properties": {"content": "b"}}::vertex,
{"id": 1688849860263940, "label": "next", "end_id": 1407374883553281,
"start_id": 1407374883553282, "properties": {}}::edge, {"id": 1407374883553281,
"label": "node", "properties": {"content": "a"}}::vertex, {"id":
1688849860263938, "label": "next", "end_id": 1125899906842625, "start_id":
1407374883553281, "properties": {}}::edge, {"id": 1125899906842625, "label":
"tail", "properties": {"name": "list01"}}::vertex]::path
(1 row)
```
**My questions**
1. The difference between sql file 1 and sql file 2 is that sql file 1
queries the list directly using a VLE cypher statement, but sql file 2 queries
the list using a function with the VLE cypher statement inside. However, the
outputs of them are different after prepending the node 'b'. Sql file 1 printed
both 'a' and 'b'. But sql file 2 printed only 'a'. Why are they different?
2. Assume that the output of sql file 1 is correct. The path printed proves
that the path is (head)->(b)->(a)->(tail). But the the VLE cypher statement
first printed 'a' then printed 'b'. Is it the expected behaviour of the VLE
that return the results not as the path order?
**Environment (please complete the following information):**
PostgreSQL 11 and AGE commit id 95ca659
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