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https://issues.apache.org/jira/browse/DERBY-3346?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12562174#action_12562174
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Daniel John Debrunner commented on DERBY-3346:
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Hit another problem with the NON_UNIQUE column. Changes for DERBY-2775 fix it
for the JDBC query but the ODBC query continues to indicate the column is
nullable. This is because the JDBC column is CAST for the ODBC query.
The CAST operator incorrectly always sets its type to nullable, even when the
source is not nullable.
E.g.
expression: 'a' - not nullable
expression CAST ('a' AS CHAR(4)) - nullable
Simple tests appear to show the CAST is working correctly:
expresion: 3 - not nullable
expression CAST (3 AS SMALLINT) - not nullable
I think this is because the bind is removing the cast node and modifying the
constant node's type, as the code for CastNode always seems to set its type to
be nullable.
> DatabaseMetaData.getIndexInfo returns the wrong nullabilty for column 4
> NON_UNIQUE
> ----------------------------------------------------------------------------------
>
> Key: DERBY-3346
> URL: https://issues.apache.org/jira/browse/DERBY-3346
> Project: Derby
> Issue Type: Bug
> Components: JDBC, SQL
> Affects Versions: 10.4.0.0
> Reporter: Daniel John Debrunner
> Assignee: Daniel John Debrunner
> Priority: Minor
>
> Derby's implementation of the NON_UNIQUE column for getIndexInfo() resolves
> to this expression:
> (CASE WHEN CONGLOMS.DESCRIPTOR.isUnique() THEN FALSE ELSE TRUE END) AS
> NON_UNIQUE
> The possible return values for this are TRUE or FALSE (this is internal SQL),
> which are both non-null constants,
> thus its type should be not nullable. A similar external SQL expression by
> itself does return the correct nullability,
> thus it seems to be a possible case where one node's nullability is affecting
> another. See DERBY-2775 and DERBY-3342. This like DERBY-3342 was found while
> fixing DERBY-2775.
> Working SQL with correct nullability:
> VALUES CASE WHEN 3=? THEN 1 ELSE 2 END
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