On Wed, 2022-06-29 at 15:23 +1200, David Rowley wrote: > Over on [1] I noticed that the user had set force_parallel_mode to > "on" in the hope that would trick the planner into making their query > run more quickly. Of course, that's not what they want since that GUC > is only there to inject some parallel nodes into the plan in order to > verify the tuple communication works. > > I get the idea that Robert might have copped some flak about this at > some point, given that he wrote the blog post at [2]. > > The user would have realised this if they'd read the documentation > about the GUC. However, I imagine they only went as far as finding a > GUC with a name which appears to be exactly what they need. I mean, > what else could force_parallel_mode possibly do? > > Should we maybe rename it to something less tempting? Maybe > debug_parallel_query? > > I wonder if \dconfig *parallel* is going to make force_parallel_mode > even easier to find once PG15 is out. > > [1] > https://www.postgresql.org/message-id/DB4PR02MB8774E06D595D3088BE04ED92E7B99%40DB4PR02MB8774.eurprd02.prod.outlook.com > [2] > https://www.enterprisedb.com/postgres-tutorials/using-forceparallelmode-correctly-postgresql
I share the sentiment, but at the same time am worried about an unnecessary compatibility break. The parameter is not in "postgresql.conf" and documented as a "developer option", which should already be warning enough. Perhaps some stronger wording in the documetation would be beneficial. I have little sympathy with people who set unusual parameters without even glancing at the documentation. Yours, Laurenz Albe
