On Feb21, 2014, at 13:44 , John Williams <jdwilliams1...@gmail.com> wrote: > I'm writing a pgsql extension in C, which is multithreaded. The SPI > connection is global, so do I have to implement a lock to make sql > queries in each thread, or can I make a connection on a per-thread basis?
Postgres backends aren't multi-threaded, and offer no support for multiple threads whatsoever. AFAIK, the only safe way to use multiple threads is to either restrict calls to *any* postgres function to only one thread, or to use a single, big mutex to prevents multiple threads from accessing postgres internals simultaneously. You should also prevent auxiliary threads from executing the signal handlers that postgres installs. See pthread_sigmask. And you'll need to make sure that everything (i.e. the whole of postgres and your extension) is built with multi-threading enabled. Otherwise, things like errno might end up not being thread-local, meaning any syscall your auxiliary threads do can interfere with postgres' error handling. You might want to check whether you can run the multi-threaded parts of your extension as a separate process, and communicate with the backend via some IPC mechanism. best regards, Florian Pflugs -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
