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From "Daniel John Debrunner (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-1748) Global case insensitive setting
Date Fri, 02 Nov 2007 18:06:50 GMT

    [ https://issues.apache.org/jira/browse/DERBY-1748?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12539654
] 

Daniel John Debrunner commented on DERBY-1748:
----------------------------------------------

One potentially easy way to provide this functionality would be to expand the values supported
by the collation JDBC attribute.

Today it supports UCS_BASIC (fixed collation based upon Unicode codepoint) or TERRITORY_BASED
(collation using the locale (territory) of the database and collation provided by a RuleBasedCollator
object obtained using the locale. The collation is set & fixed at create database time.

The TERRITORY_BASED could be expanded to allow setting the strength of the RuleBasedCollator
being used, e.g.

TERRITORY_BASED - default strength

TERRITORY_BASED:PRIMARY - strength set using collator.setStrength(Collator.PRIMARY)
TERRITORY_BASED:SECONDARY - strength set using collator.setStrength(Collator.SECONDARY)
TERRITORY_BASED:TERTIARY  - strength set using collator.setStrength(Collator.TERTIARY )
TERRITORY_BASED:IDENTICAL  - strength set using collator.setStrength(Collator.IDENTICAL)

This allows some user control of the collation and for some (most) languages will provide
case-insensitive searches.

E.g. according to the javadoc for java.text.Collator with a locale of en_US then TERRITORY_BASED:PRIMARY
will give case insensitive searches.

Apart from testing I think this would be around 20-30 lines of code:
  a) code to parse the new collation attribute values
  b) new constants for collation with strength (four new constants)
  c) code to set the strength based upon those constants.


> Global case insensitive setting
> -------------------------------
>
>                 Key: DERBY-1748
>                 URL: https://issues.apache.org/jira/browse/DERBY-1748
>             Project: Derby
>          Issue Type: New Feature
>          Components: SQL
>            Reporter: Terry
>
> By default MySQL is case insensitive in its string comparisons, as you can see from the
MySQL docs shown below. Similar functionality is available in Sybase iAnywhere and in SQLServer.
I'd like the same to be true for Derby.
> What, I wonder, are chances of that?
> I am aware that functions could be used to force comparisons in upper case but that subverts
the indexes and makes searches unacceptably long.
> If you were to ask people you might find that this is a feature whose abscence is causing
many to look elsewhere.
> thanks for all the great work,
> Terry
> The MySQL Docs say:
> -------- start quote
>  By default, MySQL searches are not case sensitive (although there are some character
sets that are never case insensitive, such as czech). This means that if you search with col_name
LIKE 'a%', you get all column values that start with A or a. If you want to make this search
case sensitive, make sure that one of the operands has a case sensitive or binary collation.
For example, if you are comparing a column and a string that both have the latin1 character
set, you can use the COLLATE operator to cause either operand to have the latin1_general_cs
or latin1_bin collation. For example:
> col_name COLLATE latin1_general_cs LIKE 'a%'
> col_name LIKE 'a%' COLLATE latin1_general_cs
> col_name COLLATE latin1_bin LIKE 'a%'
> col_name LIKE 'a%' COLLATE latin1_bin
> If you want a column always to be treated in case-sensitive fashion, declare it with
a case sensitive or binary collation. See Section 13.1.5, "CREATE TABLE Syntax". 
>     By default, the search is performed in case-insensitive fashion. In MySQL 4.1 and
up, you can make a full-text search by using a binary collation for the indexed columns. For
example, a column that has a character set of latin1 can be assigned a collation of latin1_bin
to make it case sensitive for full-text searches.
> --------------- end quote

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