On 2005-03-14, Tom Lane <[EMAIL PROTECTED]> wrote: > The 8.0 planner is intentionally sensitive to the current actual > physical sizes of tables. It sounds like you've managed to get it to > plan something on the assumption that the tables are tiny and keep > using that plan after they aren't tiny any more. The old planner had > the same kind of issue but it was far easier to hit, so "revert that > change" isn't an answer that I'm particularly interested in.
On the irc channel we were just investigating a very similar case to this (which will show up as a bug report here in due course, though not from me). It turns out that the scenario above is trivial to hit in 8.0 using referential constraints; RI triggers cache their plans, and on 8.0 the RI query is planned as a seqscan if the tables are freshly created. (On 7.4 the plan is an index scan, thanks to the default 1000 rows / 10 pages stats.) What this basically means is that you can't do even a modest size insert of new data into a fresh schema without having to either trick the planner (e.g. enable_seqscan=false before the first insert) or defer the addition of constraints until after the data load (which can be quite inconvenient in some cases). -- Andrew, Supernews http://www.supernews.com - individual and corporate NNTP services ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings
