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From Apache Wiki <wikidi...@apache.org>
Subject [Db-derby Wiki] Update of "BuiltInLanguageBasedOrderingDERBY-1478" by MamtaSatoor
Date Mon, 02 Apr 2007 02:58:12 GMT
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The following page has been changed by MamtaSatoor:
http://wiki.apache.org/db-derby/BuiltInLanguageBasedOrderingDERBY-1478

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  9)This item is related to item 11. When DVF gets called by store to create right DVD for
given formatid and collation type, for formatids associated with character datatypes, it will
first create the base character datatype class which is say SQLChar. Then it will call getValue
method on the DVD with the RuleBasedCollator corresponding to the collation type as the parameter.
(This RuleBasedCollator will be null for UCS_BASIC collation). The getValue method will return
SQLChar or CollatorSQLChar depending on whether RuleBasedCollator is null or not. getValue
is the new method which needs to be added to the interface StringDataValue.
  
- 10)Override all the collation related methods in the CollatorSQLChar. CollatorSQLChar is
a subclass of SQLChar.
+ 10)WorkHorseForCollatorDatatypes should override all the collation related methods so that
it uses the non-default Collator. All the non-default-collation-sensitive classes have an
instance of WorkHorseForCollatorDatatypes which is used to call the collation related methods.
This ensures that these collation related methods are implemented in one central place rather
than in all the collation-sensitive classes. 
  
- 11)Add subclasses for SQLVarchar, SQLLongvarchar, SQLClob. These subclasses will override
the collation related methods in their superclasses.
+ 11)CollatorSQLChar has a method called getCollationElementsForString which currently gets
called by like method. getCollationElementsForString gets the collation elements for the value
of CollatorSQLChar class. But say like method is looking for pattern 'A%' and the value of
CollatorSQLChar is 'BXXXXXXXXXXXXXXXXXXXXXXX'. This is eg of one case where it would have
been better to get collation element one character of CollatorSQLChar value at a time so we
don't go through the process of getting collation elements for the entire string when we don't
really need. This is a performance issue and could be taken up at the end of the implementation.
Comments on this from Dan and Dag can be found in DERBY-2416. 
  
- 12)CollatorSQLChar has a method called getCollationElementsForString which currently gets
called by like method. getCollationElementsForString gets the collation elements for the value
of CollatorSQLChar class. But say like method is looking for pattern 'A%' and the value of
CollatorSQLChar is 'BXXXXXXXXXXXXXXXXXXXXXXX'. This is eg of one case where it would have
been better to get collation element one character of CollatorSQLChar value at a time so we
don't go through the process of getting collation elements for the entire string when we don't
really need. This is a performance issue and could be taken up at the end of the implementation.
Comments on this from Dan and Dag can be found in DERBY-2416. 
- 
- 13)Add tests for this feature. This a broad umbrella task but I do want to mention 3 specific
tests that we should be testing
+ 12)Add tests for this feature. This a broad umbrella task but I do want to mention 3 specific
tests that we should be testing
  a)Make sure the scale of the character datatypes is always 0 and it didn't get impacted
negatively by the overloading of scale field as collation type in TypeDescriptor.
  b)Test case for recovery - have an outstanding transaction with insert/delete/updates that
affect one or more character indexes (all with a collation setting that is different from
default collation). Make sure those log records get to the log and then crash the server.
Restarting the server will then run through the recovery code and will ensure that we test
for correct collation usage at recovery time. Mike has put more info about this in DERBY-2336.
  c)CREATE VIEW should have collation type UCS_BASIC/TERRIOTRY_BASED assocatied with it's
character columns. The exact collation will be determined by what is the value of the COLLATION
attribute. This is same as what would happen for CREATE TABLE. Have a test for global temporary
tables with character colums too.
  
- 14)Make sure the space padding at the end of various character datatypes is implemented
commented correctly in javadocs. This padding is used in collation related methods. For eg
check SQLChar.stringCompare method.
+ 13)Make sure the space padding at the end of various character datatypes is implemented
commented correctly in javadocs. This padding is used in collation related methods. For eg
check SQLChar.stringCompare method.
  
  == Implemented items ==
  1)Subclasses with non-default-collation have been implemented for character types SQLChar,
SQLVarchar, SQLLongvarchar and SQLClob. The new subcalsses are called CollatorSQLChar, CollatorSQLVarchar,
CollatorSQLLongvarchar and CollatorSQLClob, respectively. They reside in derby.iapi.types
package. This work was done by revisions 516864, 516869 and 518479, 524545.

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