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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Btmap Index
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The SQL query should have the same column order in the select statement =
as
the order in the bitmap index or it will not use the index.
=20
=20
david
=20
=20
-----Original Message-----
From: Kevin Kostyszyn [mailto:kevin_at_dulcian.com]
Sent: Monday, January 08, 2001 6:50 PM
To: Multiple recipients of list ORACLE-L
Subject: Re: Btmap Index
I ran into a similar problem a while back. If the database is set to =
use
the CBO, it might not use the index. Someone on this list gave a great
reason why, perhaps the table is just very small and the CBO just =
decided to
do a full table scan instead. You could use a hint and tell it to use =
rule
based on that query and it will use the index on the where clause. =
That's
what I did. The question is, how big is the table and how much data =
does it
have in it? If it is not a lot, there really is nothing to be =
concerned
about. Oh yeah, and almost 100% positive that there is no setting in =
the
init file for the index. =20
Sincerely,
Kevin
Sent: Monday, January 08, 2001 5:45 PM
Subject: Btmap Index
Hi,
=20
Is there any init.ora parameter that needs to be turned to activate =
bitmap
indexes?
I have a bitmap index on one column C1, but when i examine the explain =
pan
of the=20
query: " select C1, b, c from table TT where C1 in ('dd','ff')" , it =
looks
like it is not using
the index but doing a full table scan...
=20
thanks
-krishna
-----Original Message-----
From: root_at_fatcity.com [mailto:root_at_fatcity.com]On Behalf Of Jacques
Kilchoer
Sent: Monday, January 08, 2001 2:01 PM
To: Multiple recipients of list ORACLE-L
Subject: RE: Date comparison question
> -----Original Message-----=20
> From: Lisa Yates [ mailto:cosnit_at_creighton.edu
<mailto:cosnit_at_creighton.edu> ]=20
> Sent: lundi, 8. janvier 2001 11:27=20
>=20
>=20
>=20
>=20
>=20
>=20
Well, I guess my suggestion that run_date may contain a "BCE" (before =
common
era) date was not the answer to your problem. Maybe I misunderstood the
issue. When you say "why doesn't the query ever return", do you mean it
returns zero rows, or do you mean that the query is taking an =
abnormally
long time? If it's taking an abnormally long time, an explain plan on =
the
two queries may reveal the cause.
Jacques R. Kilcho=EBr=20
(949) 754-8816=20
Quest Software, Inc.=20
8001 Irvine Center Drive=20
Irvine, California 92618=20
U.S.A.=20
http://www.quest.com <http://www.quest.com> =20
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> <TITLE>RE: Date comparison question</TITLE> <META content="MSHTML 5.00.2920.0" name=GENERATOR> <STYLE></STYLE> </HEAD>
<DIV><FONT face=Arial size=2>Sincerely,</FONT></DIV> <DIV><FONT face=Arial size=2>Kevin</FONT></DIV> <BLOCKQUOTE
<DIV style="FONT: 10pt arial"><B>Subject:</B> Btmap Index</DIV>
<DIV><BR></DIV>
<DIV><FONT color=#0000ff face=Arial size=2><SPAN
class=953563822-08012001>Hi,</SPAN></FONT></DIV>
<DIV><FONT color=#0000ff face=Arial size=2><SPAN
class=953563822-08012001></SPAN></FONT> </DIV>
<DIV><FONT color=#0000ff face=Arial size=2><SPAN class=953563822-08012001>Is
there any init.ora parameter that needs to be turned to activate bitmap
indexes?</SPAN></FONT></DIV>
<DIV align=left class=OutlookMessageHeader dir=ltr><FONT face=Tahoma
size=2>-----Original Message-----<BR><B>From:</B> root_at_fatcity.com
[mailto:root_at_fatcity.com]<B>On Behalf Of </B>Jacques
Kilchoer<BR><B>Sent:</B> Monday, January 08, 2001 2:01 PM<BR><B>To:</B>
Multiple recipients of list ORACLE-L<BR><B>Subject:</B> RE: Date
comparison question<BR><BR></DIV></FONT>
<P><FONT size=2>> -----Original Message-----</FONT> <BR><FONT
size=2>> From: Lisa Yates [<A
href="mailto:cosnit_at_creighton.edu">mailto:cosnit_at_creighton.edu</A>]</FONT>
<BR><FONT size=2>> Sent: lundi, 8. janvier 2001 11:27</FONT> <BR><FONT
size=2>> </FONT><BR><FONT size=2>> Why doesn't this query ever
return...</FONT> <BR><FONT size=2>> </FONT><BR><FONT size=2>> where
run_date = to_date('01-03-2001 16:34:59','mm-dd-yyyy </FONT><BR><FONT
size=2>> hh24:mi:ss')</FONT> <BR><FONT size=2>> </FONT><BR><FONT
size=2>> but this query does....</FONT> <BR><FONT size=2>>
</FONT><BR><FONT size=2>> where to_char(run_date) =
to_char(to_date('01-03-2001</FONT> <BR><FONT size=2>>
16:34:59','mm-dd-yyyy hh24:mi:ss'))</FONT> <BR><FONT size=2>>
</FONT><BR><FONT size=2>> and so does this query....</FONT> <BR><FONT
size=2>> </FONT><BR><FONT size=2>> where
to_char(run_date,'mm-dd-yyyy hh24:mi:ss') = '01-03-2001 </FONT><BR><FONT
size=2>> 16:34:59'</FONT> </P>
<P><FONT size=2>Well, I guess my suggestion that run_date may contain a
"BCE" (before common era) date was not the answer to your problem. Maybe I
misunderstood the issue. When you say "why doesn't the query ever return",
do you mean it returns zero rows, or do you mean that the query is taking
an abnormally long time? If it's taking an abnormally long time, an
explain plan on the two queries may reveal the cause.</FONT></P>
<P><FONT size=2>Jacques R. Kilchoër</FONT> <BR><FONT size=2>(949)
754-8816</FONT> <BR><FONT size=2>Quest Software, Inc.</FONT> </P>
<P><FONT size=2>8001 Irvine Center Drive</FONT> <BR><FONT size=2>Irvine,
California 92618</FONT> <BR><FONT size=2>U.S.A.</FONT> <BR><FONT size=2><A
Received on Fri Jan 19 2001 - 10:50:08 CST
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