Re: Parallel safety tagging of extension functions

On Sat, May 21, 2016 at 1:01 PM, Andreas Karlsson <andreas(at)proxel(dot)se> wrote:
> Another question which I thought of is what we should do with functions like
> pg_file_write() in adminpack.
>
> While it is perfectly fine to modify files from the parallel workers, a user
> could get race conditions if he tries to modify the same file multiple
> times. Is this a kind of problem the PARALLEL tagging should try to prevent,
> or is that something we should leave to the user?

I think there's little value in marking such things parallel-safe,
even though by some definition they may be. Parallelizing queries
involving pg_file_write() is not really a useful thing to do. What we
really want to do is nail the functions that people might be likely to
use as scan quals, plus any generally useful aggregates.

--
Robert Haas
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