Re:Re: BUG #15169: create index CONCURRENTLY conflict with othertable's COPY

but, there is no other session get any level lock with table a(creating index.). so if concurrenty create index with
tablea , at the end of the work, we can get a lock for table a and end the creating , like pg_repack? 






在 2018-04-24 23:29:52，"David G. Johnston" <david.g.johnston@gmail.com> 写道：



On Tue, Apr 24, 2018 at 8:16 AM, Andres Freund <andres@anarazel.de> wrote:



On 2018-04-24 12:29:47 +0000, PG Bug reporting form wrote:

> table a's copy will block table b's CONCURRENTLY index creating.



Yes, concurrently waits for other sessions to complete. I don't see a

bug here?



To be more specific a create index can stop processing as soon as its done its own work because it prevented any
concurrenttransactions from operating at the same time.  With concurrently those other transactions can continue to
workand thus the concurrent indexing performed by CREATE INDEX cannot know it is finished while other transactions hold
writelocks on the affected table/index.  Instead it waits "to finish" until those transactions finish.  The concurrent
indexcreation has already started and is in progress - there just isn't any communication to the client as to progress. 


David J.