Hello,
I've encountered a disturbing behaviour using the || operator on two jsonb objects extracted from subfields of a common jsonb object.
Let's take a look at this example :
with data as (
select '{
"nested1": {"lvl1_k1": "v1"},
"nested2": {"lvl2_k1":234, "lvl2_k2": "test"}
}'::jsonb as extra_values,
'{"aaa": 12}'::jsonb as j1,
'{"bbb": "azerty", "ccc": "qwerty"}'::jsonb as j2
)
select COALESCE(extra_values->'nested1', '{}')
|| COALESCE(extra_values->'nested2', '{}') as correct,
extra_values->'nested1' || extra_values->'nested2' as bad,
j1 || j2 as correct2
from data
;
I'm expecting to get the same result in columns 'correct' and 'bad', which is :
{"lvl1_k1": "v1", "lvl2_k1": 234, "lvl2_k2": "test"}
But what I'm getting in column 'bad' is only the right operand :
{"lvl2_k1": 234, "lvl2_k2": "test"}
I can recover to my expected behaviour by forcing a cast to jsonb on the second operand :
SELECT extra_values->'nested1' || (extra_values->'nested2')::jsonb
What's your opinion about this ? Is it a bug or an expected behaviour, and if so, how do you explain it ?
Thanks for sharing your knowledge !