10g Release 2. If you have any suggestions for 11g, they are welcome, an upgrade is possible, should this be resolved there. On Fri, Mar 27, 2009 at 4:47 PM, Bobak, Mark <Mark.Bobak@xxxxxxxxxxxx> wrote: > Christo, > > What version of Oracle?? > > -Mark > > -----Original Message----- > From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On > Behalf Of Christo Kutrovsky > Sent: Friday, March 27, 2009 4:41 PM > To: oracle-l > Subject: Bitmap index costing - how to influence > > Hello List, > > I am pretty much stuck on a bitmap costing problem. > > I have a query on a table with 10M rows (709MB), and the predicates > are correctly estimated to return 800 000 rows. As a result with the > famous 80/20 split, my bitmap index access path cost is ~170 000. The > full table scan cost is ~20 000. Obviously Oracle choose FTS. > > When executed with a hint, the query touches about 8000 block from the > table, and needless to say, is significantly faster. > > Any ideas on how to influence bitmap index cost, relative to full > table scan cost? Anything goes as long as it doesn't break b-tree > index costing. > > Thing's I've already considered, but somewhat ruled out > - adjust "mbrc" system statistic - event at max (128) cost is still > 133 000 vs 16 000 fts > - optimizer_index_cost_adj - i will have to set this to 10 (10 times > cheaper) for bitmaps to be used. I am concerned about proper > calculations of b-tree indexes vs full table scans > > Any other ideas? > > -- > Christo Kutrovsky > Senior DBA > The Pythian Group - www.pythian.com > I blog at http://www.pythian.com/blogs/ > -- > //www.freelists.org/webpage/oracle-l > > > > > -- Christo Kutrovsky Senior DBA The Pythian Group - www.pythian.com I blog at http://www.pythian.com/blogs/ -- //www.freelists.org/webpage/oracle-l