On Sat, Mar 18, 2017 at 10:59 AM, Petr Jelinek <petr.jeli...@2ndquadrant.com> wrote: >> shm_redirect_to_shm_mq() wasn't really designed to be used this way; >> it's designed for use by the worker, not the process that launched it. >> If an error occurs while output is redirected, bad things will happen. >> I think it would be better to find a way of sending that message to >> the queue without doing this. > > Couldn't we just create special version of pq_endmessage that sends to > shm_mq?
Yes, I think that sounds good. >> Also, I suspect this is deadlock-prone. If we get stuck trying to >> send a message to the background session while the queue is full, and >> at the same time the session is stuck trying to send us a long error >> message, we will have an undetected deadlock. That's why >> pg_background() puts the string being passed to the worker into the >> DSM segment in its entirety, rather than sending it through a shm_mq. > > Yeah I think this will need to use the nowait = true when sending to > shm_mq and chunk the message if necessary... Hmm, yeah. If you take breaks while sending to check for data that you need to receive, then you should be fine. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
