Re: Implicit coercions need to be reined in
От | Peter Eisentraut |
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Тема | Re: Implicit coercions need to be reined in |
Дата | |
Msg-id | Pine.LNX.4.30.0111221640400.766-100000@peter.localdomain обсуждение исходный текст |
Ответ на | Implicit coercions need to be reined in (Tom Lane <tgl@sss.pgh.pa.us>) |
Ответы |
Re: Implicit coercions need to be reined in
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Список | pgsql-hackers |
Tom Lane writes: > What I'd like to suggest (for 7.3 or later) is adding a boolean column > to pg_proc that indicates "can be implicit coercion". Great! I've always wished for this sort of thing. I think from this there are only a few more steps to the full SQL99 specification of user-defined casts. In particular it'd involve two boolean flags: one that means "this is a cast function" (the function is used internally for a CAST() invocation), and one for allowing it to be used for automatic conversion. We currently don't have the first one on the radar because we use the function name and argument types as the indicator. One more thing is that instead of looking up a cast function from type A to type B as "returns A, is named A, takes arg B" it could be looked up as "returns A, takes arg B, is a cast function", which would generalize this whole thing a bit more. References: SQL99 Part 2 11.49, 11.52 (I haven't read the whole thing, but I think it's the idea.) -- Peter Eisentraut peter_e@gmx.net
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