Re: 32 indexes in a table ??

Also use bitmap index in low cardinality columns if you are not expecting too many updates on that column.

dyou98_at_aol.com (D.Y.) wrote in message news:<f369a0eb.0207091452.78dc61b9_at_posting.google.com>...
> premjhere_at_yahoo.co.in (Prem J Khanna) wrote in message news:<11af2de9.0207090026.3cbe0b35_at_posting.google.com>...
> > guys,
> >
> > in my client place (8.1.6 on win2k),
> >
> > i have a table MSG which has about 9 lac records and 45 columns.
> > it has about 32 b-tree non-unique indexes.
> > no primary key is found , although a column "POSTNO" can be a
> > PK.
> >
> I've never seen any table with so many indexes.
>
> > of these 32,
> >
> > 18 columns have no values at all.i mean NULL.
> > 8 columns have 30 records .
> > 3 have some 5000 records.
> > 2 columns have 8 lac records
> > 2 has 2 lac records
> >
> > is the indexes on the first 26 columns which have negligible
> > records necessary ? can they be dropped ?
> > will not the huge no. of NULL in an indexed column bring down the
> > performance ?
> >
> If you have indexes which are created only on null columns (one or
> more of the 18) they are useless and can be dropped. Whether you need
> the other indexes depends on how you query the table. But I suspect you
> won't need more than a few for a 5000 record table. Oracle concepts
> mannual has good explanations on how indexes are created and used.
>
> > and can the index on the column ( which is of low cardinality )
> > which has 2 lac records be changed to bitmap index ?
> >
> > is too many indexes advisable in a table ?
> >
> > It's urgent.
> > kindly guide me.
> >
> > TIA.
Received on Thu Jul 11 2002 - 02:18:23 CEST