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https://issues.apache.org/jira/browse/DRILL-7096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16894571#comment-16894571
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ASF GitHub Bot commented on DRILL-7096:
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paul-rogers commented on issue #1829: DRILL-7096: Develop vector for canonical
Map<K,V>
URL: https://github.com/apache/drill/pull/1829#issuecomment-515716535
here seems to be little documentation of the design or implementation: I
find myself having to reverse engineer a design from the code. Would it be
helpful for other reviewers if we included a bit of explanation?
In particular, what is the structure of the new vector? The true map vector
seems to have a user-defined key and value type. Does this mean keys can be
integers or maps? Do the proposed map functions handle non-Varchar keys? Do
they handle repeated or map keys? If not, should the implementation restrict
key types?
How do we handle varying value types? (I have a map with, say, {name:
"Fred", balance: 123}. Would the user specify a Union? Have we fixed the many
existing problems with the Union type? Or, is the true map meant to be like a
Java map: Map<K,V>, and not a Python or JSON map with string keys and values of
any type?
A bit of documentation (a README file, a package-info file or just a Javadoc
explanation in the vector class) would help answer these questions.
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> Develop vector for canonical Map<K,V>
> -------------------------------------
>
> Key: DRILL-7096
> URL: https://issues.apache.org/jira/browse/DRILL-7096
> Project: Apache Drill
> Issue Type: Sub-task
> Reporter: Igor Guzenko
> Assignee: Bohdan Kazydub
> Priority: Major
> Fix For: 1.17.0
>
>
> Canonical Map<K,V> datatype can be represented using combination of three
> value vectors:
> keysVector - vector for storing keys of each map
> valuesVector - vector for storing values of each map
> offsetsVector - vector for storing of start indexes of next each map
> So it's not very hard to create such Map vector, but there is a major issue
> with such map representation. It's hard to search maps values by key in such
> vector, need to investigate some advanced techniques to make such search
> efficient. Or find other more suitable options to represent map datatype in
> world of vectors.
> After question about maps, Apache Arrow developers responded that for Java
> they don't have real Map vector, for now they just have logical Map type
> definition where they define Map like: List< Struct<key:key_type,
> value:value_type> >. So implementation of value vector would be useful for
> Arrow too.
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