I wrote: > You might consider whether you can write 'spa-000'::uid explicitly in your > query; that results in immediate application of the domain coercion, so > that the planner no longer sees that as a run-time operation it has to > avoid.
Hm, scratch that --- experimentation shows that the parser still produces a CoerceToDomain node in that case, not a literal of the domain type.
regression=# create domain foo as text; CREATE DOMAIN regression=# explain verbose select 'x'::foo; QUERY PLAN ------------------------------------------- Result (cost=0.00..0.01 rows=1 width=32) Output: ('x'::text)::foo (2 rows)
You could force the issue with an immutable function:
Why the rewrite doesn't reduce it? Or why parser does it?
Regards
Pavel
regression=# create function forcefoo(text) returns foo as regression-# 'begin return $1::foo; end' language plpgsql immutable; CREATE FUNCTION regression=# explain verbose select forcefoo('x'); QUERY PLAN ------------------------------------------- Result (cost=0.00..0.01 rows=1 width=32) Output: 'x'::foo (2 rows)
Marking this function as immutable is sort of a lie, because it is effectively telling the planner that you don't expect any failure from pre-evaluation of the function. But it'd get the job done, and in most situations there's no practical difference because any failure would have happened anyway at runtime.
