Re: To create or not to create that index

On Thu, Aug 17, 2023 at 8:37 PM Stefan Knecht <knecht.stefan@gmail.com> wrote:

Hello

Why does this happen?

profile_aggregates=> create index concurrently foo_idx on agg (status, foots, created_ts);


^CCancel request sent
ERROR:  canceling statement due to user request
profile_aggregates=>
profile_aggregates=>  create index concurrently foo_idx on agg (status, foots, created_ts);
ERROR:  relation " foo_idx" already exists

Are these operations not atomic ?

No, being atomic would interfere with doing things concurrently.  Per the docs:

In a concurrent index build, the index is actually entered as an “invalid” index into the system catalogs in one transaction, then two table scans occur in two more transactions.

...

If a problem arises while scanning the table, such as a deadlock or a uniqueness violation in a unique index, the CREATE INDEX command will fail but leave behind an “invalid” index.

"Problem" includes you forcibly killing it while it is running.

https://www.postgresql.org/docs/current/sql-createindex.html

David J.