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https://issues.apache.org/jira/browse/DERBY-3330?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12573347#action_12573347
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Daniel John Debrunner commented on DERBY-3330:
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Thanks for cleaning up the IndexDescriptor upgrade related code, makes it look
much cleaner.
A minor issue I have that if needed can be handled after any patch is applied
is the naming in the code of the new style of unique index.
The common theme is "uniqueWhenNotNull", when I first looked at the code I
thought this was the other way around since for index definitions I tend to
think of the DDL, not the row values. Thus:
isUnique() is true for indexes where the columns are defined NOT NULL
isUniqueWhenNotNull() is true for indexes where the columns are nullable
(but unique when the column values do not contain NULLs).
See how that can be confusing to code readers who see the code without having
been immersed in developing the code.
Not sure of a better name, re-writing to be a positive statement (always
clearer) but still referring to the values would be:
isUniqueWithDuplicateNulls()
or a positive statement referring to the column types:
isUniqueWithNullableColumns()
I think a change in name would be good for the long term readability of the
code, again it can be a follow on patch, fairly easy to do with IDE refactoring.
One more aside, it would be good to expand the definition of isUnique() and the
current isUniqueWhenNotNull() in IndexDescriptor to indicate any relationship
between them, e.g. is isUnique() true if isUniqueWhenNotNull() is true?
> provide support for unique constraint over nullable columns
> -----------------------------------------------------------
>
> Key: DERBY-3330
> URL: https://issues.apache.org/jira/browse/DERBY-3330
> Project: Derby
> Issue Type: New Feature
> Components: Store
> Affects Versions: 10.4.0.0
> Environment: all
> Reporter: Anurag Shekhar
> Assignee: Anurag Shekhar
> Attachments: BTreeController.diff, db2Compatibility.diff,
> derby-3330-testcase.diff, derby-3330.diff, derby-3330v10.diff,
> derby-3330v11.diff, derby-3330v12.diff, derby-3330v2.diff, derby-3330v3.diff,
> derby-3330v4.diff, derby-3330v5.diff, derby-3330v6.diff, derby-3330v7.diff,
> derby-3330v8.diff, derby-3330v9.diff, derbyall_report.txt,
> FunctionalSpec_DERBY-3330-V2.html, FunctionalSpec_DERBY-3330.html,
> UniqueConstraint_Implementation.html,
> UniqueConstraint_Implementation_V2.html,
> UniqueConstraint_Implementation_V3.html
>
>
> Allow unique constraint over nullable field. Right now derby support unique
> constraint only over not null columns.
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