On Fri, Dec 22, 2017 at 1:53 PM, Jeremy Finzel <finz...@gmail.com> wrote:
> I am attempting to build several indexes in parallel, guaranteeing that I > never build one on the same table twice. I understand I can't build two on > the same table at once or I will get a deadlock. However, I am also > getting a deadlock when doing several in parallel on different tables. > > Here is an example of the error I am getting: > > 2017-12-22 15:48:07.669 CST,"CREATE INDEX",2017-12-22 15:48:02 > CST,8/32,0,ERROR,40P01,"deadlock detected","Process 4470 waits for > ShareLock on virtual transaction 4/262; blocked by process 4466. > Process 4466 waits for ShareLock on virtual transaction 8/32; blocked by > process 4470. > Process 4470: CREATE INDEX CONCURRENTLY index_foo_on_created_at ON foo > USING btree (created_at); > Process 4466: CREATE INDEX CONCURRENTLY index_bar_on_id ON bar USING btree > (id);","See server log for query details.",,,,"CREATE INDEX CONCURRENTLY > index_foo_on_created_at ON foo USING btree (created_at);",,,"" > > Here is my process: > > - Kick off one index build and background 1 second apart, using a > queue table to determine what indexes to build and what is finished > - When I determine if a index can be built, I first check if there is > another already in build on target table before starting another > - After the index is built in each workflow, I mark it as built in a > queue table > > I assume that one of the indexes (the earlier transaction) is building and > taking so long that several finished indexes end up waiting, and there is > perhaps a limit to that? > Each index build needs to wait for all other transactions (Including the ones used by the other index build) to finish. So I don't think a deadlock here is unexpected. Cheers, Jeff
