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Tom Lane replied: >> So as a general rule, the system tables should be considered a special >> case as far as transactional activity? To be more precise, you are saying >> that a system table must be locked in access exclusive mode before any >> change is made to guarantee no problems occur? > No, I didn't say that --- I said that you need to lock the table whose > schema you're trying to modify, to ensure that no one else is in the > midst of accessing it using the old schema info. Sorry, I did mean the target table. >> So the oft-given advice of "UPDATE pg_class SET relhasrules = false" >> is actually completely unsafe unless the entire referenced table is >> completely locked, and unless you are using at least 8.2? > I don't recall having ever given *that* advice to anyone. But yes, > it's unsafe if there might be concurrent access to that table. The > only context I've ever seen people use this sort of thing in is > pg_restore --disable-triggers, and in that situation I think there's > an implicit assumption that no one else is busy modifying the table > you're restoring into. Not, not your advice, and perhaps not as common as SET reltriggers, but still invaluable for things like bulk loading. Thanks for the responses, I think I've finally got my head around the problem. At the very least, I've discovered another good reason to push production sites to use 8.2. - -- Greg Sabino Mullane [EMAIL PROTECTED] End Point Corporation PGP Key: 0x14964AC8 200701041708 http://biglumber.com/x/web?pk=2529DF6AB8F79407E94445B4BC9B906714964AC8 -----BEGIN PGP SIGNATURE----- iD8DBQFFnXrivJuQZxSWSsgRAlSUAJ9xSg6NBO984pBT0Ea2fAnhFdfX/QCcDXKj 2j4m8MdNCnLX5iVXz4D8AAI= =NkGM -----END PGP SIGNATURE----- ---------------------------(end of broadcast)--------------------------- TIP 7: You can help support the PostgreSQL project by donating at http://www.postgresql.org/about/donate
