On 08/22/2016 10:32 PM, Robert Haas wrote:
... 1. The number of tables for which we would need to add a duplicate, unlogged table is formidable. You need pg_attribute, pg_attrdef, pg_constraint, pg_description, pg_type, pg_trigger, pg_rewrite, etc. And the backend changes needed so that we used the unlogged copy for temp tables and the permanent copy for regular tables is probably really large. 2. You can't write to unlogged tables on standby servers, so this doesn't help solve the problem of wanting to use temporary tables on standbys. 3. While it makes creating temporary tables a lighter-weight operation, because you no longer need to write WAL for the catalog entries, there's probably still substantially more overhead than just stuffing them in backend-local RAM. So the performance benefits are probably fairly modest. Overall I feel like the development effort that it would take to make this work would almost certainly be better-expended elsewhere. But of course I'm not in charge of how people who work for other companies spend their time...
Could someone please explain how the unlogged tables are supposed to fix the catalog bloat problem, as stated in the initial patch submission? We'd still need to insert/delete the catalog rows when creating/dropping the temporary tables, causing the bloat. Or is there something I'm missing?
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