Re: DW query tuning - explain on

Mark Jamison wrote: Mark, Unless I'm misunderstanding how you intend the BDT to be used, I don't think that it substitutes for a bitmap index. I true bitmap index is an inversion index each of the nodes of which contain a bitmap of rowids (or other direct row pointers) of rows which contain that key value. The true value of a bitmap index is that if the DB engine can use multiple bitmap indexes on a single table, it can quickly determine rows that satisfy all criteria on those indexes by AND'ing the bitmaps together. Multiple criteria within a single key (ANDs and ORs can similarly be satisfied just be AND and OR operations on the bitmaps.. The resulting compound bitmap will have a bit on for each rowid that contains all of the required key values. How can adding some bit field to each row help accomplish that? What am I missing? XPS has true bitmap indexes and can indeed apply multiple index keys on a single table in the FROM clause, IDS cannot. Those abilities from XPS would be needed in IDS to make it a viable DW engine for very large databases. Currently, IDS gives respectable DW performance for smaller databases, but not VLBs. If IBM did add multi-index and bitmap indexes to IDS, then the only thing missing from making a complete Arrowhead engine would be distributed tables/databases and XPS's advanced distributed query management capabilities. Art S. Kagel > Actually, you can build a poor mans bitmap index quite easily > beginning in version 10.00.xC6 and above. > > Beginning wiht that version you have access to the Binary Datatype, > via the BDT blade. If you add a binary column to the table, and > process your values, you can then index it, and thus have an > equivalent Bitmap index. > > For some simple info describing the BDT blade and how it works, either > check the 11.10 documentation, or just read the post I did for it: > > http://www-128.ibm.com/developerworks/blogs/page/idsteam?tag=BDT > > > > > ----- Original Message ---- > From: Jack Parker <jack.parker4@verizon.net> > To: bill.abler@gmail.com; informix-list@iiug.org > Sent: Sunday, February 10, 2008 9:17:19 PM > Subject: RE: DW query tuning - explain on > > No, in dbaccess set PDQPRIORITY to 100, otherwise you are asking for 5% > (your session) of 5% (MAXPDQ) of 878MB = 2.2MB. > > Not sure what you mean by star transformation. AFAIK, there is no bitmap > index in 10 which is what is required to truly handle this query properly. > I suspect the reasons for this to be more political than technical. > > cheers > j. > > Sane ego te vocavi. Forsitan capedictum tuum desit. > > -----Original Message----- > From: informix-list-bounces@iiug.org > <mailto:informix-list-bounces@iiug.org> > [mailto:informix-list-bounces@iiug.org > <mailto:informix-list-bounces@iiug.org>]On Behalf Of > bill.abler@gmail.com <mailto:bill.abler@gmail.com> > Sent: Sunday, February 10, 2008 8:59 PM > To: informix-list@iiug.org <mailto:informix-list@iiug.org> > Subject: Re: DW query tuning - explain on > > > OK - I've tried the queries with PDQ set to 0 & 5 in dbaccess, run > times are almost exactly the same. One underlying question I have, > does this version, of IDS 10.00.FC3X6 (non-XPS) Informix support star > transformation? > _______________________________________________ > Informix-list mailing list > Informix-list@iiug.org <mailto:Informix-list@iiug.org> > http://www.iiug.org/mailman/listinfo/informix-list > > _______________________________________________ > Informix-list mailing list > Informix-list@iiug.org <mailto:Informix-list@iiug.org> > http://www.iiug.org/mailman/listinfo/informix-list > > ------------------------------------------------------------------------ > > _______________________________________________ > Informix-list mailing list > Informix-list@iiug.org > http://www.iiug.org/mailman/listinfo/informix-list > =========================================================================================== Please access the attached hyperlink for an important electronic communications disclaimer: http://www.oninit.com/home/disclaimer.php ===========================================================================================