On Wed, Nov 12, 2014 at 9:49 PM, Robert Haas <robertmh...@gmail.com> wrote: > On Tue, Nov 11, 2014 at 7:48 PM, Kouhei Kaigai <kai...@ak.jp.nec.com> wrote: >> Isn't provolatile = PROVOLATILE_IMMUTABLE sufficient? > > There are certainly things that are parallel-safe that are not > immutable. It might be the case that everything immutable is > parallel-safe. FWIW, when working on the concept of expression and clause shippability for Postgres-XC (aka the possibility to pass it safely to another backend, but in another PG node in this case), we discussed similar things and if I recall correctly we even discussed about adding a flag to pg_proc to define if a function was shippable or not. Finally what we finished with was not adding a new flag and use as rule that all the immutable functions can be safely shipped, and others not, even some stable functions that *could* be safe. Maybe Ashutosh has more comments on that, my memory may be failing. In the end, I think that you would finish with something similar. My 2c. -- Michael
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