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From "Mamta A. Satoor (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-2335) Compare character datatypes with different collation ordering.
Date Tue, 15 May 2007 20:54:17 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2335?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12496130
] 

Mamta A. Satoor commented on DERBY-2335:
----------------------------------------

Mike, I was planning of doing the javadoc fix and removing the redundant method in BaseTypeCompiler
as part of my cleanup. Didn't realize I accidentally included 2 imports. I will take care
of that too and see if anything else needs cleanup.

As for including impl reference in iapi, I am not too sure about the rules here. The advantage
of using ExpressionClassBuilder is that the reference to the method descriptor can be hold
on to because it is for per generated class level. 

The junit tests have passed fine with this patch and I am running derbyall right now. I will
go ahead and cleanup the code and check it in. If there is further concern about impl and
iapi boundaries, we can take it up as a subsequent discussion/patch.

> Compare character datatypes with different collation ordering.
> --------------------------------------------------------------
>
>                 Key: DERBY-2335
>                 URL: https://issues.apache.org/jira/browse/DERBY-2335
>             Project: Derby
>          Issue Type: Sub-task
>          Components: SQL
>    Affects Versions: 10.3.0.0
>            Reporter: Mamta A. Satoor
>         Assigned To: Mamta A. Satoor
>         Attachments: DERBY2335_correct_collation_for_constants_persistent_column_v1_diff.txt,
DERBY2335_correct_collation_for_constants_persistent_column_v1_stat.txt, DERBY2335_fix_stringCompare_Method_CollatorSQLxxx_classes_v1_diff.txt,
DERBY2335_fix_stringCompare_Method_CollatorSQLxxx_classes_v1_stat.txt, DERBY2335_More_tests_And_Fix_getNull_v1_diff.txt,
DERBY2335_More_tests_And_Fix_getNull_v1_stat.txt, DERBY2335_Use_LCC_in_ValueNode_v1_diff.txt,
DERBY2335_Use_LCC_in_ValueNode_v1_stat.txt, DERBY2335_Use_PushDataValueFactory_in_ExpressionClassBuilder_v1_diff.txt,
DERBY2335_Use_PushDataValueFactory_in_ExpressionClassBuilder_v1_stat.txt
>
>
> The parent task DERBY-1478 will enable users to have a different collation order for
user-defined character datatypes compared to UNICODE based collation, UCS_BASIC, used by system
tables. This sub-task is added to handle the case where a comparison is made between character
datatypes with different collation order. 
> For instance 
> Let's say, a database is created to use a territory based collation for character types.
And say there is a userSchema schema in that database which has a table tableInfo with column
tablename defined as VARCHAR. This tableInfo.tablename will have territory based collation
assoicated with it. And say this column is then compared with a VARCHAR column in SYS schema,
then how will the comparison happen, since the 2 columns being compared have different collation
associated with them? 
> select * from sys.systables and userSchema.tableInfo where systables.tablename = tableInfo,tablename

> Thanks to Rick for taking the time out on this issue. He had following suggestion
> </Rick comment start>
> "As I read part 2 of the SQL Standard, it looks like you need a CAST in order to compare
2 strings which have different collations bound to them. Both string operands must have the
same collation--that is my reading of Syntax rule 3b in section 9.13. Sections 6.12 and 6.1
explain how to cast the operands so that you can compare them. I think you need to write an
expression like this: 
>    WHERE userStringCol = CAST ( systemStringCol AS VARCHAR COLLATE userStringColumnsCollation
) 
> Here's an example I googled up: http://docs.openlinksw.com/virtuoso/sqlrefDATATYPES.html.
Hope this helps. 
> </Rick comment end>
> When this task is taken up, it would be good to explore Rick's suggestion.

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