Check constraints on non-immutable keys
in [PgSql]
|
From: Tom Lane on 30 Jun 2010 18:57 Peter Eisentraut <peter_e(a)gmx.net> writes: > <kibo> > "The <search condition> shall simply contain a <boolean value > expression> that is retrospectively deterministic." > This is then defined in a rather complex manner that ends up disallowing > col > now() but allowing col < now(). > </kibo> Oh, cute. Seems to have been added in SQL:2003. I guess somebody nagged them about wanting to be able to write CHECK(col <= now()). The detailed definition is amazingly laborious and yet limited, though, as it basically doesn't address the problem except for that specific case and close relatives. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
From: Robert Haas on 30 Jun 2010 19:03 On Wed, Jun 30, 2010 at 6:57 PM, Tom Lane <tgl(a)sss.pgh.pa.us> wrote: > Peter Eisentraut <peter_e(a)gmx.net> writes: >> <kibo> >> "The <search condition> shall simply contain a <boolean value >> expression> that is retrospectively deterministic." > >> This is then defined in a rather complex manner that ends up disallowing >> col > now() but allowing col < now(). >> </kibo> > > Oh, cute. �Seems to have been added in SQL:2003. �I guess somebody > nagged them about wanting to be able to write CHECK(col <= now()). > The detailed definition is amazingly laborious and yet limited, though, > as it basically doesn't address the problem except for that specific > case and close relatives. Well, solving the problem in general is equivalent to the halting problem, so... -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise Postgres Company -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
From: Tom Lane on 30 Jun 2010 19:41 Robert Haas <robertmhaas(a)gmail.com> writes: > On Wed, Jun 30, 2010 at 6:57 PM, Tom Lane <tgl(a)sss.pgh.pa.us> wrote: >> The detailed definition is amazingly laborious and yet limited, though, >> as it basically doesn't address the problem except for that specific >> case and close relatives. > Well, solving the problem in general is equivalent to the halting problem, so... So is proving determinism. They had the sense to *not* try to define what that means. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
First
|
Prev
|
Pages: 1 2 3 4 Prev: Look-behind regular expressions Next: [HACKERS] Check constraints on non-immutable keys |