On 11/03/2016 11:45, Magnus Hagander wrote: > > Coming back to the previous discussions about random() - AFAICT this > patch will introduce the random() call always (in explain_ExecutorStart): > > +if (auto_explain_log_min_duration >= 0 && nesting_level == 0) > +current_query_sampled = (random() < auto_explain_sample_ratio * > +MAX_RANDOM_VALUE); > > > Not sure what the overhead is, but wouldn't it be better to include a > check for current_query_sampled>0 in the if part of that statement? > Regardless of performance, that feels cleaner to me. Or am I missing > something?
You mean check for auto_explain_sample_ratio > 0 ? There would be a corner case if a query is sampled (current_query_sampled is true) and then auto_explain_sample_ratio is set to 0, all subsequent queries in this backend would be processed. We could add a specific test for this case to spare a random() call, but I fear it'd be overkill. Maybe it's better to document that the good way to deactivate auto_explain is to set auto_explain.log_min_duration to -1. -- Julien Rouhaud http://dalibo.com - http://dalibo.org -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers