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https://issues.apache.org/jira/browse/DRILL-6043?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16296436#comment-16296436
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Paul Rogers commented on DRILL-6043:
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Once the list passes through project, it does pick up the internal vectors:
{noformat}
`flat`(LIST:OPTIONAL) [`[DEFAULT]`(LATE:OPTIONAL),
`$data$`(LIST:OPTIONAL) ...]]]
{noformat}
But, the way this information was added is broken. Project added a vector for
the data portion of the list. But, it did remove the original "dummy" type
created when the list is created. This leaves the list with two children when
it should have one.
We must have multiple ways that we manipulate list internals, leading to these
errors.
> Nullable vector, but not List vector, adds its internal vectors to child list
> -----------------------------------------------------------------------------
>
> Key: DRILL-6043
> URL: https://issues.apache.org/jira/browse/DRILL-6043
> Project: Apache Drill
> Issue Type: Bug
> Affects Versions: 1.10.0
> Reporter: Paul Rogers
> Priority: Minor
>
> Each Drill vector has associated metadata in the form of a
> {{MaterializeField}} instance. The {{MaterializeField}} contains a list of
> children. For a Map vector, the list of children lists the vectors that make
> up the map.
> Nullable vectors use the list of children to identify the hidden vectors that
> make up the nullable vectors: {{$bits$}} and {{$values$}}.
> However, repeated vectors (including lists) also have hidden internal
> vectors: offsets and values. However, the metadata for repeated types and
> lists do not include these in the vector metadata.
> We should decide if we need metadata for the implied internal vectors.
> (Having it does cause problems since a newly-created schema for a nullable
> vector is not equal to the actual schema created by the vector itself.)
> If we don't need the internal vector metadata, remove it from the nullable
> vectors.
> But, if we do need it, add it to the repeated vectors and to lists.
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