Michael Glaesemann <grzm@seespotcode.net> writes:
> test=# select '2008-02-15' > CURRENT_DATE;
> Here, we're comparing against a date type, so Postgres treats
> '2008-02-15' as a date.
It might be worth pointing out that this is not magic,
but an application of the general rule mentioned at step 2a here:
http://www.postgresql.org/docs/8.3/static/typeconv-oper.html
In any case where Postgres is trying to interpret a binary operator,
and one input has a known type while the other is an unknown-type
literal constant, the preferred interpretation will be that the
constant has the same type as the known-type input.
In a case like 'today is ' || '2008-02-16', *both* inputs are
initially unknown-type literals. There is a fallback heuristic
that prefers to resolve such cases as type text, which is why
you get text concatenation rather than a "couldn't resolve
operator" error.
In no case does Postgres look at the content of an unknown literal
to determine its type. '2008-02-16' is not treated differently
from 'foobar'.
regards, tom lane
