"Nicholson, Brad (Toronto, ON, CA)" <bnicholson@xxxxxxx> writes: > I'm seeing a performance regression on 9.6 Beta 2 compared to 9.5.3. > The query is question is a recursive query on graph data stored as an > adjacency list. FWIW, I can't reproduce any regression with this example. I get EXPLAIN execution times like these, depending on which datatype and environment I use: 9.5: text, C locale: 9307.186 ms citext, C locale: 12541.840 ms citext, en_US.utf8 locale: 22551.332 ms HEAD: text, C locale: 9109.792 ms citext, C locale: 12251.408 ms citext, en_US.utf8 locale: 22129.683 ms The plans are all the same of course. The extra runtime for citext is presumably due to the cost of smashing strings to lowercase within citext_eq(). This is with assert-enabled builds of current branch tips, not the release versions you're working from, but I don't recall that we've changed anything recently that would be likely to affect this. Maybe you're comparing an assert-enabled beta build to a not-assert-enabled 9.5 build? > As an aside, the cost mis-estimates are very common with these types of > queries on graph data, The only error I'm noticing is a bad guess about the size of the recursive union result, which is unsurprising since it is only a guess. If you've heard of ways to estimate recursive union sizes more plausibly, maybe we could do something about that. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
