Tomasz Szypowski <tomasz.szypowski@asseco.pl> writes:
> I have got an example, in which PostgreSQL could speed up:
The reason why the first version of the view doesn't behave well
is that it's not optimized into an "append relation", because
is_simple_union_all() doesn't think that's safe:
/*
* is_simple_union_all
* Check a subquery to see if it's a simple UNION ALL.
*
* We require all the setops to be UNION ALL (no mixing) and there can't be
* any datatype coercions involved, ie, all the leaf queries must emit the
* same datatypes.
*/
Perhaps this could be improved, but it's a lot easier just to add
the cast yourself.
regards, tom lane
