Re: Bit by "commands ignored until end of transaction block" again
От | Glenn Maynard |
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Тема | Re: Bit by "commands ignored until end of transaction block" again |
Дата | |
Msg-id | bd36f99e0907230039l29b66027ibf51ae2c715a44b6@mail.gmail.com обсуждение исходный текст |
Ответ на | Re: Bit by "commands ignored until end of transaction block" again (Richard Huxton <dev@archonet.com>) |
Ответы |
Re: Bit by "commands ignored until end of transaction block"
again
(Richard Huxton <dev@archonet.com>)
Re: Bit by "commands ignored until end of transaction block" again (Adrian Klaver <aklaver@comcast.net>) Re: Bit by "commands ignored until end of transaction block" again (Craig Ringer <craig@postnewspapers.com.au>) |
Список | pgsql-sql |
On Thu, Jul 23, 2009 at 2:41 AM, Richard Huxton<dev@archonet.com> wrote: > Ah [cue light-bulb effect], I think I understand. Your function isn't in the > database is it? Surely your application knows if it's issuing BEGIN..COMMIT? I'm writing a Python library call. It has no idea whether the caller happens to be inside a transaction already, and I don't want to specify something like "always run this inside a transaction". (Callers are equally likely to want to do either, and it's bad API to force them to start a transaction--the fact that I'm using the database at al should be transparent.) > You'll have people with torches and pitchforks after you if you change > RELEASE SAVEPOINT to mean COMMIT. I might even lend them my pitchfork. RELEASE SAVEPOINT would only COMMIT the transaction *if* the savepoint that it's releasing started it. Every currently-valid case requires that a transaction is already started, so no existing code would be affected by this. SAVEPOINT a; -- implicitly issues BEGIN because one wasn't started RELEASE SAVEPOINT a; -- implicitly issues COMMIT because savepoint "a" issued the BEGIN, not the user BEGIN; SAVEPOINT a; RELEASE SAVEPOINT a; -- will not commit, because savepoint "a" didn't start the transaction Of course, there are other details--it probably shouldn't allow ROLLBACK or COMMIT on an implicit transaction block, for example. > Could it generate: "SELECT ensure_cache_contains(key,data)"? Then ten lines > of plpgsql will neatly encapsulate the problem. That plpgsql can be > automatically generated easily enough too. I don't think so, at least not without digging into internals. Django is built around knowing all data types, so it'd need to be givne types explicitly--for example, to know whether a timestamp should be formatted as a timestamp, date or time. (I do have a couple other columns here--timestamps for cache expiration, etc.) I'll have to ask Django-side if there's a public API to do this, but I don't think there is. > Ah, the joys of badly designed ORMs. The nice thing is that there seem to be > plenty of bad ones to choose from too. If your ORM doesn't handle > transactions well, the more you use it the more difficult your life will > become. I'd be tempted to tidy up your existing fixes and wrap Django's ORM > as cleanly as you can. That's assuming they're not interested in patches. The ORM on a whole is decent, but there are isolated areas where it's very braindamaged--this is one of them. They have a stable-release API-compatibility policy, which I think just gets them stuck with some really bad decisions for a long time. -- Glenn Maynard
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