On Tue, Mar 20, 2018 at 3:27 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
I think you could push the conditionality into a plpgsql function, something like (untested)
create function jsonb_elements_if_array(j jsonb) returns setof jsonb as $$ begin if jsonb_typeof(j) = 'array' then return query select jsonb_array_elements(j); end if; end$$ strict immutable language plpgsql;
Note that this gives *no* elements, rather than a single NULL value, if the input isn't an array --- but that seems to me to make more sense than your existing code anyhow. If you disagree, add "else return next null::jsonb".
I think I will just introduce a separate column (until now I was trying to squeeze 2 different kinds of data - JSON array of objects and a string - into the one column)... I believe Adrian had suggested it before :-)