On Mon, 2020-08-03 at 19:23 +0300, Stelios Sfakianakis wrote: > I am trying to implement a FDW in Postgres for accessing a web api and I would > like to keep information like for example the total number of requests submiited. > Ideally these data should be kept “per-user” and of course with the proper locking > to eliminate race conditions. So the question I have is how to design such a global > (but per user and database) state, using the C FDW API of Postgres. I have gone > through the API and for example I see various fdw_private fields in the query > planning structures and callbacks but these do not seem to be relevant to my requirements. > Another possiblity seems to be to use shared memory > (https://www.postgresql.org/docs/12/xfunc-c.html#id-1.8.3.13.14) but it is even > less clear how to do it. > > So is there any simple way to do implement such shared thread/process safe state? I would create a table as part of the extension and use SPI to store the data there. Yours, Laurenz Albe
