On 2016-01-15 13:17:12 +0300, Vladimir Sitnikov wrote: > There is a finding that insert(x) values(y);insert(x) values(z); is > 2-4 times slower than insert(..) values(y),(z); > see [1], [2].
If you indeed just mean statements like above, without begin/commit, a large portion of the overhead will be transactional overhead. But I guess you mean there's a transaction surrounding it? If not, quite possibly what you're describing is client round trip latency? How exactly are these issued? There'll be some overhead of running two statements rather than one, but if you have neither added transactional overhead, nor latency issues, the difference isn't *that* big in my experience. > Is it something that was discussed previously? Yes. I think the biggestoverhead here is that the executor startup includes too many indirect (linked lists) datastructured, that allocated each round. And that some datastructures are computed at execution time (ExecTypeFromTL I'm looking at you). Unfortunately changing that is not a small project. Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
