From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Dennis Björklund <db(at)zigo(dot)dhs(dot)org> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Implicit coercions, choosing types for constants, etc (yet again) |
Date: | 2002-11-11 16:56:35 |
Message-ID: | 2710.1037033795@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
=?ISO-8859-1?Q?Dennis_Bj=F6rklund?= <db(at)zigo(dot)dhs(dot)org> writes:
> It seems to me that one would like to have a polymorphic typesystem with
> constraints to handle overloading, subtyping or whatever is needed in
> SQL.
What we have now is indeed pretty ad-hoc, but a full-blown type
inference system might be overkill. Not sure. It would be interesting
to look into it.
> Is there anywhere I can read about the typesystem in SQL in general and
> postgresql in particular?
There's the user's guide
http://developer.postgresql.org/docs/postgres/typeconv.html
and there's the source code (see src/backend/parser/, particularly
parse_coerce.c, parse_func.c, parse_oper.c). Not much in between
I'm afraid, but the source code is reasonably well-commented.
regards, tom lane
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