Hi Jonathan, Brilliant example. Thanks very much for this. (And yes, I meant the first 15th for each index, not the first 15th for the entire database!)
And yes, I do think that 15 indexes is a bit excessive but I can't help it at the moment (3rd party, packaged application...) Does this mean that I'm reading another myth? Couldn't confirm it on metalink. Ta, Leng. ----------------------- From: "Jonathan Lewis" <[EMAIL PROTECTED]> Date: Wed, 21 Jan 2004 07:20:30 -0000 Subject: Re: Oracle 8.1.7 can only use the first 15th indexes? drop table t1; create table t1 nologging pctfree 50 pctused 50 as select 1 n01, 1 n02, 1 n03, 1 n04, 1 n05, 1 n06, 1 n07, 1 n08, 1 n09, 1 n10, 1 n11, 1 n12, 1 n13, 1 n14, 1 n15, rownum n16, lpad(rownum,10) v1 from all_objects ; create index i01 on t1(n01); create index i02 on t1(n02); create index i03 on t1(n03); create index i04 on t1(n04); create index i05 on t1(n05); create index i06 on t1(n06); create index i07 on t1(n07); create index i08 on t1(n08); create index i09 on t1(n09); create index i10 on t1(n10); create index i11 on t1(n11); create index i12 on t1(n12); create index i13 on t1(n13); create index i14 on t1(n14); create index i15 on t1(n15); create index i16 on t1(n16); analyze table t1 estimate statistics; set autotrace traceonly explain; select v1 from t1 where n16 = 99; set autotrace off The execution path uses I16 on my system. It would be possible to produced test cases that failed to use the 16th index, of course, and some of them could look quite convincingly as if the 16th index should be used. But it only takes one counter-example ... (I assume the report intended to say the first 15 indexes on a specific table, 'cos the data dictionary alone has rather more than 15 indexes). Regards Jonathan Lewis ---------------------------------------------------------- Leng Kaing Email: [EMAIL PROTECTED] Phone: +61-3-9203-7589 Mobile: +61-417-371-348 -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Kaing, Leng INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
