On 2005-05-30, Neil Conway <[EMAIL PROTECTED]> wrote: > On Wed, 2005-03-23 at 10:04 -0500, Tom Lane wrote: >> I think last night's discussion makes it crystal-clear why I felt that >> this hasn't been sufficiently thought through. Please revert until the >> discussion comes to a conclusion. > > Are there any remaining objections to reapplying this patch?
I've run into a few questions recently that might be relevent to the issue of DDL locking in general and therefore possibly this change in particular. The most significant one is to do with the pg_get_*def functions and their consistency, or otherwise, with explicit scans of the system catalogs. The problem here of course is that the pg_get_*def functions mostly (but not exclusively) use the syscache and therefore see data relative to SnapshotNow, whereas the queries that are invoking them are likely to be doing explicit scans of the catalog tables within the transaction's active snapshot (and for a long-running serializable transaction such as pg_dump, these may be some way apart). The obvious place to look for failure modes is to see whether pg_dump can be made to fail by deleting something (index, perhaps?) that it is expecting to find, and see whether it chokes (pg_get_indexdef will elog if the index doesn't exist in SnapshotNow). Dropping a view might be another case where this can be made to fail. -- Andrew, Supernews http://www.supernews.com - individual and corporate NNTP services ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings
