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https://issues.apache.org/jira/browse/ORC-625?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17560632#comment-17560632
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Hao Fu commented on ORC-625:
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the benefits provided by this change is limited, because it is cheap to compare
DynamicByteArray, and its not likely that we have large amounts of nodes with a
long common prefix who also have a parent-child relationship.
On the other hand, the cost of this change is huge – an additional field that
needs to be maintained especially during rotation, it is important but
complicated to have thorough testing against it as well. Does not seem like a
desirable change at all.
> Improve dictionary lookup by marking common prefixes
> ----------------------------------------------------
>
> Key: ORC-625
> URL: https://issues.apache.org/jira/browse/ORC-625
> Project: ORC
> Issue Type: Improvement
> Reporter: Ted Xu
> Priority: Major
>
> Dictionary lookup is slow if there are common prefixes, e.g.,
> {code:java}
> http://foo.bar/a1
> http://foo.bar/a2
> http://foo.bar/a3
> {code}
> It is because dictionary lookup will require comparing values from head every
> time the RedBlack tree finds a new node.
> If the RedBlack tree is able to mark common prefix to parent, we can skip
> some redundant compare.
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