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https://issues.apache.org/jira/browse/DRILL-5283?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15876356#comment-15876356
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Julian Hyde commented on DRILL-5283:
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Consider calling this "is empty". MDX and HBase/Phoenix have concepts of empty
cells, and we should share concepts wherever possible. Otherwise you no longer
have a data model; you are bubbling up details of the data format.
> Support "is not present" as subtype of "is null" for JSON data
> --------------------------------------------------------------
>
> Key: DRILL-5283
> URL: https://issues.apache.org/jira/browse/DRILL-5283
> Project: Apache Drill
> Issue Type: Improvement
> Affects Versions: 1.10.0
> Reporter: Paul Rogers
>
> JSON files consist of a series of "objects", each of which has name/value
> pairs. Values can be in one of three states:
> * Not present (the value does not appear)
> * Null (the name appears and the value is null)
> * Non-null (the field is one of the JSON data types)
> Drill, however, has only a single null state and so Drill collapses "not
> present" and "null" into the same state.
> The not-present and present-but-null states work identically for calculations
> inside Drill. But, when doing a CTAS from JSON to JSON, the collapsed state
> means that the user does not get out of Drill what was put in: all null
> values either appear as null values, or do not appear at all (depending on
> Drill version.)
> This ticket asks to repurpose the "bit" fields in nullable vectors. Rename
> the vector to "nullState". Then, use these values:
> * 0: value is set
> * 1: value is null
> * 3: value is not present
> The column is null if the null state is non-zero. The column is not null if
> the null state is 0.
> This change requires reversing the "polarity" of the bit field, and so is a
> major change.
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