Обсуждение: BITMAP INDEXES...

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.

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,
Pennsylvania19073
 

<p>Bitmapped indexes are good for weakly constrained queries. Else B+tree indexes are better any day. <p>Also I guess
bitmappedindexes work better when there is an OR predicate on different columns in a query. <p> <b><i>Bruce Momjian
</i></b>wrote:<blockquote style="BORDER-LEFT: #1010ff 2px solid; MARGIN-LEFT: 5px; PADDING-LEFT: 5px"><br />See the
emailabout bitmapped indexes linked to from the TODO list item<br />on bitmaps. Bitmap indexes allow arbitrary indexes
tobe combined into<br />a single index. Btree indexes can not be combined.<br /><br
/>---------------------------------------------------------------------------<br/><br />Rajesh Kumar Mallah. wrote:<br
/>>Hi,<br />> <br />> I have learnt from certain texts that bitmap indexes are very useful for<br />> large
DSS(decesion support systems).<br />> <br />> bitmap indexes are currently not available in postgresql.<br />>
<br/>> My question is in what way is a normal btree index in pgsql<br />> inferior to bitmap indexes (found in
oraclefor example).<br />> <br />> is it just in terms of space requirements for performance too?<br />> <br
/>><br />> regds<br />> mallah.<br />> <br />> <br />> -- <br />> Rajesh Kumar Mallah,<br />>
ProjectManager (Development)<br />> Infocom Network Limited, New Delhi<br />> phone: +91(11)6152172 (221) (L)
,9811255597(M)<br />> <br />> Visit http://www.trade-india.com ,<br />> India's Leading B2B eMarketplace.<br
/>><br />> <br />> <br />> ---------------------------(end of broadcast)---------------------------<br
/>>TIP 2: you can get off all lists at once with the unregister command<br />> (send "unregister
YourEmailAddressHere"to majordomo@postgresql.org)<br />> <br /><br />-- <br />Bruce Momjian |
http://candle.pha.pa.us<br/>pgman@candle.pha.pa.us | (610) 359-1001<br />+ If your life is a hard drive, | 13 Roberts
Road<br/>+ Christ can be your backup. | Newtown Square, Pennsylvania 19073<br /><br />---------------------------(end
ofbroadcast)---------------------------<br />TIP 4: Don't 'kill -9' the postmaster</blockquote><p><br /><hr size="1"
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