Ah, yes, that seem to be the explanation!
So it would seem that indeed it was my misunderstanding of the operator.
select '{"a": [1,2]}'::jsonb @> '{"a": [1]}'::jsonb;
?column?
----------
t
(1 row)
select '{"a": [1,2]}'::jsonb @> '{"a": [2,1,2]}'::jsonb;
?column?
----------
t
(1 row)
I was not aware of "possibly after discarding some non-matching array elements or object key/value pairs from the containing object. But remember that the order of array elements is not significant when doing a containment match, and duplicate array elements are effectively considered only once." and was expecting array equality to be the comparison. Good to know!
Many thanks
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@rotamap.net <mailto:brian@rotamap.net>
>
> Rotamap
> www.rotamap.net <https://www.rotamap.net>
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--
Adrian Klaver
adrian.klaver@aklaver.com