Re: [HACKERS] walsender & parallelism

On 21/04/17 03:40, Andres Freund wrote:
> 
> Since [1] walsender (not receiver as commit message says) can execute
> SQL queries.  While doing some testing of [2] I noticed that SQL queries
> in walsender get stuck if parallelism is used - I have not investigated
> why that is yet, but it surely is an issue.  On first blush I'd suspect
> that some signalling is not wired up correctly (cf. am_walsender branches
> in PostgresMain() and such).

Looks like SIGUSR1 being different is problem here - it's normally used
to . I also noticed that we don't handle SIGINT (query cancel).

I'll write proper patch but can you try to just use
procsignal_sigusr1_handler for SIGUSR1 in walsender.c to see if it fixes
the issue?

BTW while looking at the code, I don't understand why we call
latch_sigusr1_handler after calling SetLatch(MyLatch), shouldn't just
the SetLatch be enough (they both end up calling sendSelfPipeByte()
eventually)?

--  Petr Jelinek                  http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training &
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