On 4/21/05, Tom Lane <[EMAIL PROTECTED]> wrote: > Christopher Kings-Lynne <[EMAIL PROTECTED]> writes: > > Is this totally rad bitmap index support going in? :D Does it require > > new index types or does it work with existing ones, etc? > > Works with the existing ones. It's the same idea that's been discussed > several times, eg > http://archives.postgresql.org/pgsql-hackers/2005-02/msg00867.php
I scanned the archives but couldn't find a direct answer to something, though I seem to remember it being discussed at the beginning of the "bitmap index" planning. Will the new Bitmap[Or|And] nodes work with lossy index types? Specifically, I'd like to experiment with tsearch2 and "&" type queries and joining the results of a ts2 index scan to a btree index scan, but I seem to remember you (Tom) saying that the in-memory bitmaps would only be useful for btree indexes. I hope I'm mis-remembering... :) > > It's sort of working now, but since I don't have any planner frontend > code yet except for a truly ugly kluge in orindxpath.c, the only cases > it can deal with are simple ORs: > [snip NEW query plan] > Total runtime: 16.913 ms > (10 rows) > > This is only marginally faster than the equivalent 8.0 plan: > [snip 8.0 query plan] > Total runtime: 18.712 ms > (3 rows) > > although it should scale better to large numbers of tuples. > It will also keep long lists of ORs from turning what would have been a >10% index scan into a seq scan, yes? I suppose there is some balance that needs to be calculated on number-of-conditions-per-index-scan vs startup-cost-of-X-index-scans. E.g., if you have table with 10M rows and an IN clause with 500 elements, it might be better to start 20 index scans with 25 condition each instead of a single big index scan (what we do now if the cost isn't too high), 500 index scans (what a simple "spin off a scan per condition" algo would do, and what it _looks_ like the new code did to your test query...), or a seq scan. > Things will get more interesting once we can AND the results of > unrelated indexes ... I can't wait! How close to initial testing is the AND stuff for unrelated indexes? Could this bitmapping code be used to combine indexes from different tables, say in a large UNION or inherited table setup? > > regards, tom lane > -- Mike Rylander [EMAIL PROTECTED] GPLS -- PINES Development Database Developer http://open-ils.org ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])
