Negative indices on arrays seem to return nothing/null

[selendym]

Describe the bug
Negative indices on arrays seem to return nothing/null.

How are you accessing AGE (Command line, driver, etc.)?
With psql from the docker image. One container for the server and another one for the client.

What data setup do we need to do?

select * from ag_catalog.create_graph('g');

What is the necessary configuration info needed?
Just the docker image built from master branch.

What is the command that caused the error?

select * from ag_catalog.cypher('g', $$ with [0, 1, 2, 3] as l return l[-1] $$) as (r0 ag_catalog.agtype);

The above returns (note the empty line):

 r0 
----
 
(1 row)

Compare with:

select * from ag_catalog.cypher('g', $$ with [0, 1, 2, 3] as l return l[3] $$) as (r0 ag_catalog.agtype);
select * from ag_catalog.cypher('g', $$ with [0, 1, 2, 3] as l return l[-1..] $$) as (r0 ag_catalog.agtype);

which return:

 r0 
----
 3
(1 row)

and:

 r0  
-----
 [3]
(1 row)

Expected behavior
The negative index should work as described in: https://age.apache.org/docs/master/intro/types.html#negative-index-access

Environment (please complete the following information):

• env: docker
• branch: master
• commit: 6fbdfa8

[jrgemignani]

I will take a look

[jrgemignani]

I'm not sure how this happened. There will be a patch to fix this shortly.

[jrgemignani]

This has been corrected, and is available, in the master branch -

psql-11.5-5432-pgsql=# select * from ag_catalog.cypher('g', $$ with [0, 1, 2, 3] as l return l[-1] $$) as (r0 ag_catalog.agtype);
 r0
----
 3
(1 row)

[selendym]

Thanks for the quick fix!

[selendym]

Not sure if this is related, but seems very similar:

select * from ag_catalog.cypher('g', $$ with {k0: [0, 1], k1: [2, 3]} as m return m.k0[1] $$) as (r0 ag_catalog.agtype);
--  r0 
-- ----
--  1
-- (1 row)

select * from ag_catalog.cypher('g', $$ with {k0: [0, 1], k1: [2, 3]} as m return m.k0[-1] $$) as (r0 ag_catalog.agtype);
--  r0 
-- ----
--  
-- (1 row)

select * from ag_catalog.cypher('g', $$ with {k0: [0, 1], k1: [2, 3]} as m return m.k0[-1..] $$) as (r0 ag_catalog.agtype);
-- ERROR:  slice must access a list

Note the second part, where the result is missing, and the third, which results in an error (while it likely should not).

[selendym]

Nested arrays seem to have similar problems:

select * from ag_catalog.cypher('g', $$ with [[0, 1], [2, 3]] as l return l[0][1] $$) as (r0 ag_catalog.agtype);
--  r0 
-- ----
--  1
-- (1 row)

select * from ag_catalog.cypher('g', $$ with [[0, 1], [2, 3]] as l return l[0][-1] $$) as (r0 ag_catalog.agtype);
--  r0 
-- ----
--  
-- (1 row)

select * from ag_catalog.cypher('g', $$ with [[0, 1], [2, 3]] as l return l[0][-1..] $$) as (r0 ag_catalog.agtype);
--     r0    
-- ----------
--  [[0, 1]]
-- (1 row)

Note the second part, where the result is missing, and the third, which doesn't seem to make sense.

[jrgemignani]

Yeah, it is in the same access operator functions. It is getting the wrong size of the returned array, since it is in a binary format.

[jrgemignani]

The other issue, with the slice operator, needs to be fixed as well. It was do to some inadvertent code changes.

[jrgemignani]

There is a pending patch to correct this. It should be applied within the next few days.

[selendym]

Thanks. Feel free to close this ticket when that gets merged.