[jira] Updated: (DERBY-2335) Compare character datatypes with different collation ordering.

["Mamta A. Satoor (JIRA)" <ji...@apache.org>]

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

Mamta A. Satoor updated DERBY-2335:
-----------------------------------

    Attachment: DERBY2335_correct_collation_for_constants_persistent_column_v1_stat.txt
                DERBY2335_correct_collation_for_constants_persistent_column_v1_diff.txt

Attaching patch(DERBY2335_correct_collation_for_constants_persistent_column_v1_diff.txt) which does couple of things
1)It puts the correct collation type for character constants and for persistent character columns. For character constants, the collation type will be the collation type of the schema in which the query is getting compiled. This happens in 
CharConstantNode.bindExpression. The setting of collation type for the persistent columns happens in a constructor for the DataTypeDescriptor. This could be found in the patch which has changes for DataTypeDescriptor and TypeDescriptorImpl.
2)Collation related methods (like and stringCompare) on collation sensitive DVDs has been copied into WorkHorseForCollatorDatatypes. These methods get called by CollatorSQLxxx classes.
3)The final change went into CollationTest. The change now allows this test to test collations for Norway, English and Polish.
I will add more tests for these changes in a subsequent 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
>
>
> 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.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.