The || operator for the jsonb type has a surprising behaviour.
Instead of appending the right operand "as is" to the left operand,
it has a magic behaviour if the right operand is an array,
in which case it will append the items of the array,
instead of appending the array itself as a single value.
Example:
SELECT '[10,20]'::jsonb || '30'::jsonb;
[10, 20, 30]
SELECT '[10,20]'::jsonb || '[30]'::jsonb;
[10, 20, 30]
Since [10, 20, [30]] is desired in our case, we must use jsonb_insert() to work-around the problem in a not very nice way:
SELECT jsonb_insert('[10,20]'::jsonb,'{-1}','[30]'::jsonb,TRUE);
[10, 20, [30]]
Suggestions welcome if there is a better way to solve this problem.
Best regards,
Joel
