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https://issues.apache.org/jira/browse/DRILL-7096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16916789#comment-16916789
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ASF GitHub Bot commented on DRILL-7096:
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agozhiy commented on issue #1829: DRILL-7096: Develop vector for canonical
Map<K,V>
URL: https://github.com/apache/drill/pull/1829#issuecomment-525344202
I think we have to support backward compatibility by adding an option. Users
could already use the old data representation style in their queries, and now
they will need to be rewritten.
For example, this won't work anymore:
```select t.c.`value` from (select flatten(x.fields.map) c from x```
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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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