Greets, [Ugh, sent one with uncompressed patch. Seems to be swallowed(No failure msg?). Ignore it if it surfaces.]
The attached patch extends pg_am by adding two methods, "scan for insert" and "insert from scan". These methods are meant to provide an index user with the ability to do conditional insertions based on the results of a conclusive locking scan--a scan that not only finds a match, but resolves its actual existence(what _bt_check_unique does), and makes any necessary locks to warrant later insertion by a call to insertfromscan. (It should also be noted that insertions are aborted by giving the insertfromscan method an InvalidItemPointer instead of adding another method, ie "abortinsertscan".) I'm sending this to hackers instead of patches, because it's not complete(I know it's broken in the some of the new places), and, most importantly, I want to know if this is actually the appropriate general direction to travel in. Not to mention that I have probably missed something and I hope that someone will give me my due whackings with The Clue Stick. :P These new index interfaces are meant to provide the necessary functionality for doing conditional index insertions that will likely aid in any implementation of error logging, and other features(merge?). I have failed to find much discussion on this, so if there is a good thread about, please point me at it. The most recent discussion of something along these lines was Martijn's thread about providing non-btree indexes with uniqueness: http://archives.postgresql.org/pgsql-hackers/2006-01/msg00541.php (However, I doubt that this patch would actually help with deferred constraints or giving GiST/hash uniqueness.) This patch is mostly incremental, and doesn't make many alterations to existing code for the time being; the most significant alteration was restructuring a bit of _bt_check_unique(_bt_evaluate in this patch) to work for both scanforinsert and doinsert. (This is probably a good thing as this code is all pretty new to me.) [Sorry about some of the whitespace changes in the patch, remnants from an overzealous version.] Any thoughts and directions would be appreciated. -- Regards, James William Pye
ciinsert.patch.gz
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