Hi Gianni! Thank you for your attention and response!
>> I used the (more recent) patches posted by Gianni Ciolli in 2008 and >> currently am in the process of porting those to master HEAD -- like I >> promised. > > Back in 2008 the PostgreSQL project wasn't using git, and I wasn't > either; hence that patch is the best starting point I can find. Ok, fine. However, while I do not find the mail at the moment, I think, someone said, he fixed the VACUUM. Additionally, the Wiki lists Simon and Jonah as the last authors, pretending they prepared a patch for 8.5. >> IIRC, it was already shown that bitmap indexes can speed up TPC-H >> queries. I will compare B+-tree, bitmap, and encoded bitmap indexes. > > I think what Albe meant (also what we attempted back then, if memory > serves me, but without reaching completion) is a set of tests which > show a significant benefit of your implementation over the existing > index type implementations in PostgreSQL, to justify the increased > complexity of the source code. > > The kind of test I have in mind is: a big table T with a > low-cardinality column C, such that a btree index on C is > significantly larger than the corresponding bitmap index on the same > column. > > Create the bitmap index, and run a query like > > SELECT ... FROM T WHERE C = ... > > more than once; then you should notice that subsequent scans are much > faster than the first run, because the index is small enough to fit > the shared memory and will not need to be reloaded from disk at every > scan. > > Then drop the bitmap index, and create a btree index on the same > column; this time the index will be too large and subsequent scans > will be slow, because the index blocks must be reloaded from disk at > every scan. > > Hope that helps; Is that, what your bmi-perf-test.tar.gz from 2008 does? I did not look into that. I will at least do something like you just described plus some TPC-H test. As the encoding helps against the cardinality problems, I will also draw comparisons with different cardinalities. Yours sincerely, Daniel -- Daniel Bausch Wissenschaftlicher Mitarbeiter Technische Universität Darmstadt Fachbereich Informatik Fachgebiet Datenbanken und Verteilte Systeme Hochschulstraße 10 64289 Darmstadt Germany Tel.: +49 6151 16 6706 Fax: +49 6151 16 6229 -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
