Re: JSONB operator unanticipated behaviour

On 5/18/23 06:17, Brian Mendoza wrote:
> Hello,
>
> I have encountered unanticipated behaviour with a JSONB operator, and
> wanted to make sure I am not misunderstanding its intended use.
>
> When using the @> operator, I get this result.
>
> select '{"a": [1]}'::jsonb @> '{"a": []}'::jsonb;
>  ?column?
> ----------
>  t
> (1 row)
>
> However, given the phrasing in the documentation, I would have expected
> False.
>
> "Does the left JSON value contain the right JSON path/value entries at
> the top level?"
>
> Particularly given the following:
>
> select '[1]'::jsonb = '[]'::jsonb;
>  ?column?
> ----------
>  f
> (1 row)
>
> So the keys are the same, the values (when compared directly) are not,
> but @> returns True. Have I misunderstood the usage of the operator?
>
> The above queries have been run on postgres 14, if that helps.

Have you looked at the containment examples?:

https://www.postgresql.org/docs/current/datatype-json.html#JSON-CONTAINMENT

I'm thinking this:

-- A top-level key and an empty object is contained:
SELECT '{"foo": {"bar": "baz"}}'::jsonb @> '{"foo": {}}'::jsonb;

and/or this

"The general principle is that the contained object must match the
containing object as to structure and data contents, possibly after
discarding some non-matching array elements or object key/value pairs
from the containing object. "

applies.

>
> --
> Brian Mendoza
> brian(at)rotamap(dot)net <mailto:brian(at)rotamap(dot)net>
>
> Rotamap
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--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com