Ron <ronljohnsonjr@xxxxxxxxx> writes: > On 3/17/20 12:19 PM, David G. Johnston wrote: >> There is a nice big bold warning callout in the documentation that covers >> this explicitly. >> https://www.postgresql.org/docs/12/manage-ag-tablespaces.html >>> Warning >>> Placing a tablespace on a temporary file system like a RAM disk risks the >>> reliability of the entire cluster. > But aren't temporary files removed when you restart Postgres? (I'm assuming > that temp_tablespaces is treated "the same" as data/pgsql_tmp. Is that a > false assumption?) I think the main issue is that there's no mechanism preventing you from putting regular (non-temp) tables into the "temporary" tablespace. If you do, crash recovery will get very unhappy when it tries to replay updates for those tables and they're not there. There are probably additional issues having to do with the tablespace directory(s) disappearing. That, you could maybe finesse by having the postmaster start script re-create any missing directories. All in all, I wouldn't try it without careful pre-testing of what happens after the RAM disk gets wiped. People have asked about this before, so maybe it'd be an idea to make an explicit concept of a temp tablespace that only accepts temp tables, and do whatever is needful to make that robust. But I've not heard of any work towards that. regards, tom lane
