On Wed, Apr 20, 2022 at 12:50 PM PG Doc comments form < nore...@postgresql.org> wrote:
> The following documentation comment has been logged on the website: > > Page: https://www.postgresql.org/docs/14/sql-createfunction.html > Description: > > The page does not mention what is the default behavior whenever a function > is replaced while the same function is being used in another > query/transaction. > > Does the query fail? Does the 'CREATE OR REPLACE' operation fail? Does the > query finish before the function is replaced? > > As a side note, my interest in this came from our need to use 'C-Language > Functions', aka binary functions, so it would be neat to also add what is > the behavior on those as well, if there's any difference. > IIUC pg_proc is administered using MVCC behavior just like any other table. What you experience will be subject to your isolation mode but in no case will a single command's execution see different versions nor will such execution prevent the "replace"ment of the function with a newer version. Absent guidance to the contrary I wouldn't expect C language functions to behave any differently than any others. But that just pertains to the "REPLACE" aspect. You need to read the notes about C language functions to get the rest of the story (and you likely wouldn't need to "replace" a C-langauge function entry because of this different loading/compiling mechanism). Namely: https://www.postgresql.org/docs/current/xfunc-c.html#XFUNC-C-DYNLOAD In short, C-language functions, referenced simply by name and module, and pre-compiled, do not have a mechanism to invalidate the cache like pl/pgsql functions do. Other languages may involve yet other dynamics. David J.
