Teodor Sigaev wrote: >> What other constraints are there on such non-in-core indexex? Early (2005) >> GIST indexes were very painful in production environments because vacuuming >> them held locks for a *long* time (IIRC, an hour or so on my database) on >> the indexes locking out queries. Was that just a shortcoming of the >> implementation, or was it a side-effect of them not supporting >> recoverability. > > GiST concurrent algorithm is based on Log Sequence Number of WAL and that > was the reason to implement WAL (and recoverability) first in GiST.
Hmm, IIRC it is based on a monotonically increasing number. It could have been anything. LSN was just a monotonically increasing number that would be available if WAL was implemented first (or in parallel). Of course, there's no much point in an index that's easily corrupted, so I understand the desire to implement WAL too -- I'm just pointing out that concurrency could have been developed independently. -- Alvaro Herrera http://www.CommandPrompt.com/ The PostgreSQL Company - Command Prompt, Inc. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
