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https://issues.apache.org/jira/browse/DRILL-5657?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16181832#comment-16181832
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ASF GitHub Bot commented on DRILL-5657:
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Github user paul-rogers commented on the issue:
https://github.com/apache/drill/pull/914
Added final development stage to this PR. This is a minor implementation
tweak. The result set loader internals for maps held redundant map vectors. In
the final vector container, each map must be represented by a map (or repeated
map) vector. But, because the result set loader handles projection and
overflow, the set of columns that a map writer works with is a superset of
those that appear in the output container. For this reason, there turns out to
be no reason to maintain these "redundant" map vectors.
For repeated map vectors, we must maintain the offset vector. The code
already did this; we just strip off the enclosing repeated map vector.
> Implement size-aware result set loader
> --------------------------------------
>
> Key: DRILL-5657
> URL: https://issues.apache.org/jira/browse/DRILL-5657
> Project: Apache Drill
> Issue Type: Improvement
> Affects Versions: Future
> Reporter: Paul Rogers
> Assignee: Paul Rogers
> Fix For: Future
>
>
> A recent extension to Drill's set of test tools created a "row set"
> abstraction to allow us to create, and verify, record batches with very few
> lines of code. Part of this work involved creating a set of "column
> accessors" in the vector subsystem. Column readers provide a uniform API to
> obtain data from columns (vectors), while column writers provide a uniform
> writing interface.
> DRILL-5211 discusses a set of changes to limit value vectors to 16 MB in size
> (to avoid memory fragmentation due to Drill's two memory allocators.) The
> column accessors have proven to be so useful that they will be the basis for
> the new, size-aware writers used by Drill's record readers.
> A step in that direction is to retrofit the column writers to use the
> size-aware {{setScalar()}} and {{setArray()}} methods introduced in
> DRILL-5517.
> Since the test framework row set classes are (at present) the only consumer
> of the accessors, those classes must also be updated with the changes.
> This then allows us to add a new "row mutator" class that handles size-aware
> vector writing, including the case in which a vector fills in the middle of a
> row.
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