On 2019-Sep-28, James Coleman wrote: > I believe caveats like this are worth calling out rather than > expecting users to have to understand the implementation details an > work out the implications on their own.
I agree. > I read Alvaro as referring to the fact that the docs already call out > the following: > > > Regular index builds permit other regular index builds on the same > > table to occur simultaneously, but only one concurrent index build > > can occur on a table at a time. Yeah, that's what I was understanding. BTW I think there's an approach that could alleviate part of this problem, at least some of the time: whenever CIC runs for an index that's not on expression and not partial, we could set the PROC_IN_VACUUM flag. That would cause it to get ignored by other processes for snapshot purposes (including CIC itself), as well as by vacuum. I need to take some time to research the safety of this, but intuitively it seems safe. Even further, I think we could also do it for regular CREATE INDEX (under the same conditions) provided that it's not run in a transaction block. But that requires even more research/proof. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
