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https://issues.apache.org/jira/browse/ACCUMULO-1627?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13780178#comment-13780178
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Bill Havanki commented on ACCUMULO-1627:
----------------------------------------
See [discussion on
ACCUMULO-1734|https://issues.apache.org/jira/browse/ACCUMULO-1734?focusedCommentId=13780097&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13780097]
for background.
The method {{Mutation.equals(Mutation)}} is problematic for implementing
{{equals()}} properly in a subclass. In short, for some object {{o}} of a
subclass type {{SubMutation}}, a call to {{o.equals(m)}} where {{m}} is a
{{Mutation}} will be bound to {{Mutation.equals(Mutation)}}, not
{{SubMutation.equals(Object)}}. This is because the {{Mutation}} method has a
more specific argument type, so the compiler prefers it over the proper one in
the subclass. This is a problem for preserving symmetry for {{equals()}} as
well as for checking additional fields in the subclass.
{code:java}
Mutation m = /* some mutation */;
SubMutation sm = /* some other mutation */;
sm.equals(m); /* <- bound to Mutation.equals(Mutation) */
{code}
To remedy this I had thought to protect/rename {{Mutation.equals()}},
relegating it to a utility comparison method which it appears to be. However,
as Keith suspected, this would break ABI compatibility. Code compiled against
the old version would throw {{NoSuchMethodError}}.
Another option is to have each {{Mutation}} subclass also override
{{equals(Mutation)}}. It's messy but it should work.
So, what is the best path according to the development policies for Accumulo?
"Fix" the API at the expense of breaking the ABI, or introduce (modest) warts
to work with what already exists?
Thanks all.
> Add hashcode() and equals() to ConditionalMutation
> --------------------------------------------------
>
> Key: ACCUMULO-1627
> URL: https://issues.apache.org/jira/browse/ACCUMULO-1627
> Project: Accumulo
> Issue Type: Sub-task
> Components: client, tserver
> Reporter: Keith Turner
> Assignee: Bill Havanki
> Labels: newbie
> Fix For: 1.6.0
>
>
> ConditionalMutation should define equals() and hashcode() methods that
> consider the conditions. Its parent class defines those methods, so it
> should.
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