Casting 和 MySQL 到 Postgres 的迁移

Question

We're in the process of migrating from MySQL to Postgres and have come across a few queries that we're struggling with a little:

MySQL:

MAX(groups.id) IS NOT NULL AND MIN(groups.parent_id IS NULL) as parent_type

Postgres:

(MAX(groups.id) IS NOT NULL AND (MIN((groups.parent_id IS NULL)::int))::bool)::int as parent_type

The Postgres query works, but is there a way to avoid the explicit casting there?

Answer 1

you could declare a version of min that works on booleans.

Create AGGREGATE min( x boolean )  (
   stype=boolean,
   sfunc=booland_statefunc,
   initcond=true
);

or you could just use the bool_and aggregate.

MAX(groups.id) IS NOT NULL AND bool_and(groups.parent_id IS NULL) as parent_type