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From "Mike Matrigali (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5367) Stale data retrieved when using new collation=TERRITORY_BASED:PRIMARY feature
Date Fri, 23 Sep 2011 22:29:26 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5367?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13113813#comment-13113813

Mike Matrigali commented on DERBY-5367:

i reviewed the latest patch and it looks good to me.  I agree that overhead should be basically
"free" now with the code working off the
stored conglomerate info and not having to recalculate it.

It is great that your test case both tries the newly created conglomerate and shuts down the
database and restarts testing the read conglomerate
from disk case.

> Stale data retrieved when using new collation=TERRITORY_BASED:PRIMARY feature
> -----------------------------------------------------------------------------
>                 Key: DERBY-5367
>                 URL: https://issues.apache.org/jira/browse/DERBY-5367
>             Project: Derby
>          Issue Type: Bug
>          Components: Store
>    Affects Versions:,
>         Environment: Mac OS X, Windows
>            Reporter: Brett Wooldridge
>            Assignee: Kristian Waagan
>            Priority: Critical
>             Fix For:
>         Attachments: derby-5367-1a-update_row_fully.diff, derby-5367-1b-update_row_fully.diff,
derby-5367-1b-update_row_fully.stat, derby-5367-2a-minimal_fix.diff, derby-5367-3a-update_field_by_field_preview.diff,
derby-5367-4a-fix_with_optimization_improved.diff, derby-5367-4b-fix_with_optimization_improved.diff,
> Our product recently upgraded to version in order to take advantage of the new
'case-insensitive' mode offered by Derby in the form of the "collation=TERRITORY_BASED:PRIMARY"
connection parameter.
> Unfortunately, we have run into an issue whereby stale data appears to be retrieved from
an index, even though the data in the table itself has changed.
> You can see this issue in the IJ session below.  The database in question was created
using this Java parameter when invoking IJ:
> -Dij.database=jdbc:derby:test;create=true;collation=TERRITORY_BASED:PRIMARY
> Here is the IJ session:
> CONNECTION0* - 	jdbc:derby:test
> * = current connection
> ij> CREATE TABLE tag (
>     tag VARCHAR(255) NOT NULL,
>     CONSTRAINT tag_pk PRIMARY KEY (tag_id),
>     CONSTRAINT tag_tag_unique UNIQUE (tag)
> );
> 0 rows inserted/updated/deleted
> ij> -- first insert a value 'Test', note the upper-case 'T' in 'Test'
> ij> INSERT INTO tag (tag) VALUES ('Test');
> 1 row inserted/updated/deleted
> ij> SELECT * FROM tag;
> TAG_ID     |TAG                                                                     
> --------------------------------------------------------------------------------------------------------------------------------------------
> 1          |Test                                                                    
> 1 row selected
> ij> -- Now delete the row
> ij> DELETE FROM tag WHERE tag='Test';
> 1 row inserted/updated/deleted
> ij> -- You could run another SELECT here to verify it is gone, but it is.
> ij> -- Now insert a new value 'test', note the lower-case 't' in 'test'
> ij> INSERT INTO tag (tag) VALUES ('test');
> 1 row inserted/updated/deleted
> ij> -- Now verify that the table contains only the lower-case version: 'test'
> ij> SELECT * FROM tag;
> TAG_ID     |TAG                                                                     
> --------------------------------------------------------------------------------------------------------------------------------------------
> 2          |test                                                                    
> 1 row selected
> ij> -- Now, here is the bug.
> ij> SELECT tag FROM tag;
> TAG                                                                                 
> --------------------------------------------------------------------------------------------------------------------------------
> Test                                                                                
> 1 row selected
> ij> 
> Note in the last SELECT we specify the 'tag' column specifically.  When we 'SELECT *',
Derby performs a table-scan and the result is correct.  However, when we 'SELECT tag', Derby
appears to use the index created for the 'tag_tag_unique' unique constraint.  As an optimization
Derby, like many databases, will use values directly from the index in the case where the
index covers all requested columns.
> The bigger question is, why doesn't the DELETE action cause the entry in the tag_tag_unique
index to be deleted?  Is this a further optimization?  If so, it is imperative that the index
at least be updated when the new value is inserted.
> This is rather a severe bug for us that causes stale data to be returned.

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