Re: [PROPOSAL] Shared Ispell dictionaries

On Sun, Mar 25, 2018 at 12:18:10AM -0400, Tom Lane wrote:
> My thought was (a) the ROLLBACK case is ok, because the next use of
> the dictionary will reload it, and (b) the reload-concurrently-with-
> DROP case is annoying, because indeed it leaks, but the window is small
> and it probably won't be an issue in practice. We would need to be
> sure that the DSM segment goes away at postmaster restart, but given
> that I think it'd be tolerable. Of course it'd be better not to have
> the race, but I see no easy way to prevent it -- do you?

I'm not sure that I understood the second case correclty. Can cache
invalidation help in this case? I don't have confident knowledge of cache
invalidation. It seems to me that InvalidateTSCacheCallBack() should
release segment after commit.

But cache isn't invalidated if a backend was terminated after a
dictionary reloading. on_shmem_exit() could help, but we need a leaked
dictionaries list for that.

P.S. I think it isn't right to release all dictionaries segment in
InvalidateTSCacheCallBack(). Otherwise any DROP can release all
segments. It would be worth to release a specific dictionary.

--
Arthur Zakirov
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company