Trouble matching a nested value in JSONB entries

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.

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