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https://issues.apache.org/jira/browse/DERBY-4658?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12879720#action_12879720
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Knut Anders Hatlen commented on DERBY-4658:
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The patch looks fine to me. Some minor comments, though:
In BooleanConstantNode.init(), would it be better to pass Boolean.TRUE as the
second argument to super.init()? That's the argument that specifies
nullability. Perhaps that would also remove the need to call
setNullability(true) in CastNode?
The tests look fairly complete, but they all use true/false/unknown in
lowercase. Would it be worthwhile to add a test case to verify that strings
with upper case or mixed case also can be cast to boolean?
And, a nit, this change in BooleanConstantNode.init() is unnecessary since
(arg1 instanceof Boolean) implies (arg1 != null):
- if (arg1 instanceof Boolean)
+ if ( (arg1 != null) && (arg1 instanceof Boolean) )
Perhaps, for clarity, it may be better to have the null case first, though:
if (arg1 == null) {
...
} else if (arg1 instanceof Boolean) {
...
} else {
...
}
> Allow explicit casts of string values to BOOLEAN
> ------------------------------------------------
>
> Key: DERBY-4658
> URL: https://issues.apache.org/jira/browse/DERBY-4658
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Reporter: Rick Hillegas
> Assignee: Rick Hillegas
> Attachments: derby-4658-01-aa-booleanCasts.diff
>
>
> The SQL Standard allows strings to be explicitly cast to BOOLEAN values.
> Strings are the only type (other than BOOLEAN itself) which can be cast to
> BOOLEAN. As part of our expanding support for the BOOLEAN datatype, we should
> allow these casts.
> Casting string types to boolean is defined by part 2, section 6.12 (<cast
> specification>), general rule 20:
> a) Trim whitespace off the string
> b) Then apply the rules in section 5.3 (<literal>). This means that the
> trimmed string must be 'TRUE', 'FALSE', or 'UNKNOWN', regardless of case.
> c) Otherwise, raise an exception.
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