Article ID: 823514
Article Last Modified on 10/25/2005
APPLIES TO
- Microsoft SQL Server 2000 Enterprise Edition
- Microsoft SQL Server 2000 Developer Edition
- Microsoft SQL Server 2000 Standard Edition
- Microsoft SQL Server 2000 Desktop Engine (Windows)
- Microsoft SQL Server 2000 Enterprise Edition
SYMPTOMS
If you have a set of predicates in the following form
(a = b) && (a = constant)
there is an implied redundant predicate (b = constant) that can be added. The absence of this implied predicate can make the query run slowly.
An enhancement has been made to SQL Server to add this redundant predicate for semi joins, anti-semi joins, inner joins, and outer joins.
RESOLUTION
Service pack information
To resolve this problem, obtain the latest service pack for Microsoft SQL Server 2000. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
290211 How to obtain the latest SQL Server 2000 service pack
Hotfix information
The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.
Date Time Version Size File name
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31-May-2003 18:45 2000.80.818.0 78,400 Console.exe
25-Jun-2003 01:01 2000.80.818.0 33,340 Dbmslpcn.dll
25-Apr-2003 02:12 786,432 Distmdl.ldf
25-Apr-2003 02:12 2,359,296 Distmdl.mdf
30-Jan-2003 01:55 180 Drop_repl_hotfix.sql
23-Jun-2003 22:40 2000.80.837.0 1,557,052 Dtsui.dll
23-Jun-2003 22:40 2000.80.837.0 639,552 Dtswiz.dll
24-Apr-2003 02:51 747,927 Instdist.sql
03-May-2003 01:56 1,581 Inst_repl_hotfix.sql
08-Feb-2003 06:40 2000.80.765.0 90,692 Msgprox.dll
01-Apr-2003 02:07 1,873 Odsole.sql
05-Apr-2003 01:46 2000.80.800.0 62,024 Odsole70.dll
07-May-2003 20:41 2000.80.819.0 25,144 Opends60.dll
02-Apr-2003 21:48 2000.80.796.0 57,904 Osql.exe
02-Apr-2003 23:15 2000.80.797.0 279,104 Pfutil80.dll
22-May-2003 22:57 19,195 Qfe469571.sql
12-Jun-2003 16:37 1,083,989 Replmerg.sql
04-Apr-2003 21:53 2000.80.798.0 221,768 Replprov.dll
08-Feb-2003 06:40 2000.80.765.0 307,784 Replrec.dll
05-May-2003 00:05 1,085,874 Replsys.sql
01-Jun-2003 01:01 2000.80.818.0 492,096 Semobj.dll
31-May-2003 18:27 2000.80.818.0 172,032 Semobj.rll
29-May-2003 00:29 115,944 Sp3_serv_uni.sql
01-Jun-2003 01:01 2000.80.818.0 4,215,360 Sqldmo.dll
07-Apr-2003 17:44 25,172 Sqldumper.exe
19-Mar-2003 18:20 2000.80.789.0 28,672 Sqlevn70.rll
02-Jul-2003 00:18 2000.80.834.0 180,736 Sqlmap70.dll
08-Feb-2003 06:40 2000.80.765.0 57,920 Sqlrepss.dll
23-Jun-2003 22:40 2000.80.837.0 7,553,105 Sqlservr.exe
08-Feb-2003 06:40 2000.80.765.0 45,644 Sqlvdi.dll
25-Jun-2003 01:01 2000.80.818.0 33,340 Ssmslpcn.dll
01-Jun-2003 01:01 2000.80.818.0 82,492 Ssnetlib.dll
01-Jun-2003 01:01 2000.80.818.0 25,148 Ssnmpn70.dll
01-Jun-2003 01:01 2000.80.818.0 158,240 Svrnetcn.dll
31-May-2003 18:59 2000.80.818.0 76,416 Svrnetcn.exe
30-Apr-2003 23:52 2000.80.816.0 45,132 Ums.dll
02-Jul-2003 00:19 2000.80.834.0 98,816 Xpweb70.dll
Note Because of file dependencies, the most recent hotfix or feature that contains the files may also contain additional files.
STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.This problem was first corrected in Microsoft SQL Server 2000 Service Pack 4.
MORE INFORMATION
When you apply a hotfix or service pack that contains this fix, the SQL Server optimizer automatically introduces the implied predicate and may remove the corresponding join predicate.
The example that is mentioned in the "Symptoms" section shows a join between a and b. In this example, after optimization the predicate looks like the following:
(a = constant) and (b = constant)
When the original predicate is from a multicolumn key, the simplified expression may remove one of the original join keys. For example, the predicate t1.a = t2.a && t1.b = t2.b && t1.c = constant is changed to t1.b = t2.b && t1.a = constant && t2.a = constant. If column a is the leading column of a multicolumn index, you cannot use a multicolumn density match for cardinality estimation. Additionally, this may cause query plans where the query plan seeks on only the leading index column and applies the remaining filter criteria as residual filters in a WHERE clause on the index seek line or in a WHERE clause for the join operator. For example, the query plan seeks on t1.a = constant. In this scenario, there may be greater disk input/output load and increased CPU utilization. In SQL Server 2000 SP4, you can disable this optimization through trace flag 9061.
Keywords: kbbug kbfix kbsqlserv2000presp4fea kbqfe kbsqlserv2000presp4fix kbhotfixserver KB823514
