Trouble matching a nested value in JSONB entries

On Wed, Jun 20, 2018 at 10:06 PM, Enrico Thierbach <eno@open-lab.org> wrote:

Hi list,

I have some trouble matching a value in a JSONB object against multiple
potential matches.

Lets say, I have a table with an id, and a metadata JSONB column, which
holds data like the following

1 | {"group_id": 1}
2 | {“group_id": 1}
3 | {“group_id": 2}
4 | {“group_id": 3}

I would like to run a query which gives me the result of SELECT id FROM
mytable WHERE metadata->>’group_id’ IN (1,2). Now, obviously I could use
this query, but I
would like to get away without an explicit index on metadata->>’group_id’,
and I was hoping to find something using the JSONB containment operators,
with support
of a gist or gin index.

The following seems to work

select * from mytable where (metadata @> '{"group_id":1}')

but only with a single value to match.

I could, of course, also “denormalize” the query a la

select * from mytable where (metadata @> '{"group_id":1}') OR (metadata @>
'{"group_id”:2}’)

but this seems to call for long execution times; also, depending on the
number of different tag names and values to match this could really explode
into quite a
large query.

Stackoverflow suggests the use of ANY

select * from mytable where (tags->'group_id' @> ANY( ARRAY
['1','3']::jsonb[] ) );

https://dba.stackexchange.com/questions/130699/postgresql-json-query-array-against-multiple-values

This seems to work - but doesn’t that require a group_id specific index
again?

Anything I overlooked?

Best,
/eno

PS: Please note that I am currently at postgres 9.5. An update, if
necessary, would be possible though.

Upgrade, please !

I have only master 11beta2 right now:

select * from qq where js @> '{"group_id":1}';
id | js
----+-----------------
1 | {"group_id": 1}
2 | {"group_id": 1}
(2 rows)

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Oleg,

1 | {"group_id": 1}
2 | {“group_id": 1}
3 | {“group_id": 2}
4 | {“group_id": 3}

PS: Please note that I am currently at postgres 9.5. An update, if
necessary, would be possible though.

Upgrade, please !

I have only master 11beta2 right now:

select * from qq where js @> '{"group_id":1}';
id | js
----+-----------------
1 | {"group_id": 1}
2 | {"group_id": 1}
(2 rows)

thanks for your answer. Your code does work fine on 9.5 already; what I
would like to achieve is to get records where the group_id entry is 1 or
2, and a fear that

select * from mytable where (metadata @> '{"group_id":1}') OR
(metadata @> '{"group_id”:2}’)

- while doable - would not make the best use of existing indices.

Any more ideas?
Best,
/eno