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From "Mamta A. Satoor (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-3926) Incorrect ORDER BY caused by index
Date Wed, 29 Apr 2009 18:12:30 GMT

     [ https://issues.apache.org/jira/browse/DERBY-3926?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Mamta A. Satoor updated DERBY-3926:
-----------------------------------

    Attachment: script3WithUserFriendlyIndexNames.sql

I am attaching a newer version of script3.sql The new script is called script3WithUserFriendlyIndexNames.sql
The only changes made to script3.sql are to use user-friendly index names so that it is easier
to understand the query which is using index names through optimizer overrides to demonstrate
the buggy behavior. Hopefully it will be easier to read the query plan as well. The query
to see the problem is as follows

SELECT table1.id, table2.value, table3.value FROM --DERBY-PROPERTIES joinOrder=FIXED
table3 -- DERBY-PROPERTIES index=nonUniqueOnValue_Table3
, table2 -- DERBY-PROPERTIES index=nonUniqueOnValue_Table2
, table1
WHERE table1.id=table2.id AND table2.name='PageSequenceId' 
AND table1.id=table3.id 
AND table3.name='PostComponentId' 
AND table3.value='21857' ORDER BY table2.value;


> 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
>            Reporter: Tars Joris
>            Assignee: Mamta A. Satoor
>         Attachments: derby-reproduce.zip, script3.sql, script3WithUserFriendlyIndexNames.sql,
test-script.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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