Pavel> Hi Pavel> I have a value '400 days 30 sec':: interval
Pavel> I don't understand why cast
Pavel> postgres=# select '400days 30sec'::interval minute to second;
...
Pavel> What is sense of this feature?
As far as I know it only exists because of the sql spec, and the implementation has never been complete or working. I think it does affect some input parsing cases, there are some nasty hacks here and there to support it, but given that our intervals don't behave like the spec's ones anyway, there seems to be little motivation to make it work fully.
yes - it looks little bit bizarre
These work, for example:
select interval '4' year to month; -- 4 months select interval '4' hour; -- 4 hours select interval '4' hour to second; -- 4 seconds select '4'::interval year to month; -- 4 months etc.