09.09.2015, 18:53, Andrew Dunstan kirjoitti:
On 09/08/2015 09:54 AM, Andrew Dunstan wrote:
On 09/05/2015 02:47 AM, Oskari Saarenmaa wrote:
There was a long thread about concatenating jsonb objects to each
other, but that discussion didn't touch concatenating other types.
Currently jsonb_concat always just returns the other argument if one
of arguments is considered empty. This causes surprising behavior
when concatenating scalar values to empty arrays:
os=# select '[]'::jsonb || '1'::jsonb;
1
os=# select '[]'::jsonb || '[1]'::jsonb;
[1]
os=# select '[]'::jsonb || '1'::jsonb || '2'::jsonb;
[1, 2]
os=# select '0'::jsonb || '1'::jsonb;
[0, 1]
os=# select '{"x": "y"}'::jsonb || '[1]'::jsonb;
[{"x": "y"}, 1]
os=# select '{"x": "y"}'::jsonb || '1'::jsonb;
ERROR: invalid concatenation of jsonb objects
Attached a patch to fix and test this. Also added a test case for
concatenating two scalar values which currently produces an array..
I'm not sure that behavior makes sense, but didn't want to change
that in this patch as I guess someone could consider that feature
useful.
This looks correct. Barring objection I'll apply this shortly.
Actually, I'm not sure the test is sufficient here. It looks to me like
we should only be taking this fast path if one operand is an empty array
and the other is a non-scalar array.
Otherwise we get things like this (second case is wrong, I think):
andrew=# select '[]'::jsonb || '"a"';
?column?
----------
["a"]
andrew=# select '[]'::jsonb || '{"a":"b"}';
?column?
------------
{"a": "b"}
andrew=# select '[1]'::jsonb || '{"a":"b"}';
?column?
-----------------
[1, {"a": "b"}]
It looks wrong, but I'm not sure what's right in that case. I think
it'd make sense to just restrict concatenation to object || object,
array || array and array || scalar and document that. I doubt many
people expect their objects to turn into arrays if they accidentally
concatenate an array into it. Alternatively the behavior could depend
on the order of arguments for concatenation, array || anything -> array,
object || array -> error.
/ Oskari
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