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From "Mamta A. Satoor (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3926) Incorrect ORDER BY caused by index
Date Tue, 23 Jun 2009 21:45:07 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12723318#action_12723318
] 

Mamta A. Satoor commented on DERBY-3926:
----------------------------------------

Kathey, I looked through the diff and like you said, it may have to do with no way of using
optimizer overrides to have the optimizer use the specific join order. One other thing that
can be done(though not necessary) is to run it on other codelines without optimizer overrides
to see if we similar diff there.

> Incorrect ORDER BY caused by index
> ----------------------------------
>
>                 Key: DERBY-3926
>                 URL: https://issues.apache.org/jira/browse/DERBY-3926
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.1.3.3, 10.2.3.0, 10.3.3.1, 10.4.2.0
>         Environment: Checked into 10.3. This will still go to 10.2 and 10.1
>            Reporter: Tars Joris
>            Assignee: Mamta A. Satoor
>             Fix For: 10.3.3.1, 10.4.2.1, 10.5.1.2, 11.0.0.0
>
>         Attachments: d3926_repro.sql, derby-3926_10.3_mergeattempt.txt, derby-reproduce.zip,
DERBY3926_notforcheckin_patch1_051109_diff.txt, DERBY3926_notforcheckin_patch1_051109_stat.txt,
DERBY3926_notforcheckin_patch2_051109_diff.txt, DERBY3926_patch3_051509_diff.txt, DERBY3926_patch3_051509_stat.txt,
DERBY3926_patch4_051519_diff.txt, DERBY3926_patch4_051519_stat.txt, DERBY3926_patch5_052709_diff.txt,
DERBY3926_patch5_052709_stat.txt, DERBY3926_patch6_060309_diff.txt, DERBY3926_patch6_060309_stat.txt,
script3.sql, script3WithUserFriendlyIndexNames.sql, test-script.zip, wisconsin_10.1_result.zip
>
>
> I think I found a bug in Derby that is triggered by an index on a large column: VARCHAR(1024).
I know it  is generally not a good idea to have an index on such a large column.
> I have a table (table2) with a column "value", my query orders on this column but the
result is not sorted. It is sorted if I remove the index on that column.
> The output of the attached script is as follows (results should be ordered on the middle
column):
> ID                  |VALUE        |VALUE
> ----------------------------------------------
> 2147483653          |000002       |21857
> 2147483654          |000003       |21857
> 4294967297          |000001       |21857
> While I would expect:
> ID                  |VALUE        |VALUE
> ----------------------------------------------
> 4294967297          |000001       |21857
> 2147483653          |000002       |21857
> 2147483654          |000003       |21857
> This is the definition:
> CREATE TABLE table1 (id BIGINT NOT NULL, PRIMARY KEY(id));
> CREATE INDEX key1 ON table1(id);
> CREATE TABLE table2 (id BIGINT NOT NULL, name VARCHAR(40) NOT NULL, value VARCHAR(1024),
PRIMARY KEY(id, name));
> CREATE UNIQUE INDEX key2 ON table2(id, name);
> CREATE INDEX key3 ON table2(value);
> This is the query:
> SELECT table1.id, m0.value, m1.value
> FROM table1, table2 m0, table2 m1
> WHERE table1.id=m0.id
> AND m0.name='PageSequenceId'
> AND table1.id=m1.id
> AND m1.name='PostComponentId'
> AND m1.value='21857'
> ORDER BY m0.value;
> The bug can be reproduced by just executing the attached script with the ij-tool.
> Note that the result of the query becomes correct when enough data is changed. This prevented
me from creating a smaller example.
> See the attached file "derby-reproduce.zip" for sysinfo, derby.log and script.sql.
> Michael Segel pointed out:
> "It looks like its hitting the index ordering on id,name from table 2 and is ignoring
the order by clause."

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