Received: from localhost (postgresql.org [64.49.215.8]) by postgresql.org (Postfix) with ESMTP id 5D3A74759A1 for ; Thu, 22 Aug 2002 12:26:53 -0400 (EDT) Received: from web21403.mail.yahoo.com (web21403.mail.yahoo.com [216.136.232.73]) by postgresql.org (Postfix) with SMTP id B011F47545C for ; Thu, 22 Aug 2002 12:26:52 -0400 (EDT) Message-ID: <20020822162657.48019.qmail@web21403.mail.yahoo.com> Received: from [203.200.17.99] by web21403.mail.yahoo.com via HTTP; Thu, 22 Aug 2002 09:26:57 PDT Date: Thu, 22 Aug 2002 09:26:57 -0700 (PDT) From: imtiaz sm Subject: Re: BITMAP INDEXES... To: Bruce Momjian , "Rajesh Kumar Mallah." Cc: pgsql-sql@postgresql.org In-Reply-To: <200208221430.g7MEUdA27489@candle.pha.pa.us> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-1269688950-1030033617=:47949" X-Virus-Scanned: by AMaViS new-20020517 X-Archive-Number: 200208/315 X-Sequence-Number: 9161 --0-1269688950-1030033617=:47949 Content-Type: text/plain; charset=us-ascii Bitmapped indexes are good for weakly constrained queries. Else B+tree indexes are better any day. Also I guess bitmapped indexes work better when there is an OR predicate on different columns in a query. Bruce Momjian wrote: See the email about bitmapped indexes linked to from the TODO list item on bitmaps. Bitmap indexes allow arbitrary indexes to be combined into a single index. Btree indexes can not be combined. --------------------------------------------------------------------------- Rajesh Kumar Mallah. wrote: > Hi, > > I have learnt from certain texts that bitmap indexes are very useful for > large DSS (decesion support systems). > > bitmap indexes are currently not available in postgresql. > > My question is in what way is a normal btree index in pgsql > inferior to bitmap indexes (found in oracle for example). > > is it just in terms of space requirements for performance too? > > > regds > mallah. > > > -- > Rajesh Kumar Mallah, > Project Manager (Development) > Infocom Network Limited, New Delhi > phone: +91(11)6152172 (221) (L) ,9811255597 (M) > > Visit http://www.trade-india.com , > India's Leading B2B eMarketplace. > > > > ---------------------------(end of broadcast)--------------------------- > TIP 2: you can get off all lists at once with the unregister command > (send "unregister YourEmailAddressHere" to majordomo@postgresql.org) > -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster --------------------------------- Do You Yahoo!? HotJobs, a Yahoo! service - Search Thousands of New Jobs --0-1269688950-1030033617=:47949 Content-Type: text/html; charset=us-ascii

Bitmapped indexes are good for weakly constrained queries. Else B+tree indexes are better any day.

Also I guess bitmapped indexes work better when there is an OR predicate on different columns in a query.

Bruce Momjian wrote:

See the email about bitmapped indexes linked to from the TODO list item
on bitmaps. Bitmap indexes allow arbitrary indexes to be combined into
a single index. Btree indexes can not be combined.

---------------------------------------------------------------------------

Rajesh Kumar Mallah. wrote:
> Hi,
>
> I have learnt from certain texts that bitmap indexes are very useful for
> large DSS (decesion support systems).
>
> bitmap indexes are currently not available in postgresql.
>
> My question is in what way is a normal btree index in pgsql
> inferior to bitmap indexes (found in oracle for example).
>
> is it just in terms of space requirements for performance too?
>
>
> regds
> mallah.
>
>
> --
> Rajesh Kumar Mallah,
> Project Manager (Development)
> Infocom Network Limited, New Delhi
> phone: +91(11)6152172 (221) (L) ,9811255597 (M)
>
> Visit http://www.trade-india.com ,
> India's Leading B2B eMarketplace.
>
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 2: you can get off all lists at once with the unregister command
> (send "unregister YourEmailAddressHere" to majordomo@postgresql.org)
>

--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073

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