drop table if exists test; drop table if exists tmap; create table test( id int8, vf float8, vb bool ); create table tmap( id int8, mapped_to int8 ); insert into tmap values(1, 1); insert into tmap values(2, 2); insert into test with tmp as (select 1::int8 id, '123.4'::text v) select t.id, case m.mapped_to when 1 then v::float8 else null end, case m.mapped_to when 2 then v::bool else null end from tmp t join tmap m on m.id = t.id;
I think this has something to do with the CTE used here. In preprocess_expression, we do not know the value of m.mapped_to, so we cannot tell the test condition is constant FALSE. Thus we need go on processing the result. But thanks to the CTE, we know t.v is const '123.4'::text, and we want to convert it to boolean, which triggers the error.
