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https://issues.apache.org/jira/browse/DRILL-7143?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16811885#comment-16811885
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ASF GitHub Bot commented on DRILL-7143:
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arina-ielchiieva commented on issue #1726: DRILL-7143: Support default value
for empty columns
URL: https://github.com/apache/drill/pull/1726#issuecomment-480590998
@paul-rogers let me summarize new blank handling strategy.
We introduce new column property `drill.blank-as`. It can have four values:
`blank-as`, `null`, `0`, `simple`. User can indicate which strategy to use in
column schema. For example:
`create or replace schema (id int, amount int properties { 'drill.blank-as'
= 'simple' }) for table dfs.tmp.text_table`
If no blank strategy is indicated, behavior is the following:
1. for columns which are not indicated in schema, `blank-as` strategy will
be used. I suggest, we rename `blank-as` value to `blank`. For example:
`property { 'drill.blank-as' = 'blank' }. Why do you think?
2. for nullable columns indicated in schema, `null` strategy will be used.
3. for non-nullable columns indicated in schema with or without default
value, which strategy will be used? `0` or `simple`? So far I don't see much
difference between both, maybe we don't need one of them?
I have left some other comments in the PR, once we clarify this issue and
address code review comments, PR will be good to go.
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> Enforce column-level constraints when using a schema
> ----------------------------------------------------
>
> Key: DRILL-7143
> URL: https://issues.apache.org/jira/browse/DRILL-7143
> Project: Apache Drill
> Issue Type: Improvement
> Affects Versions: 1.16.0
> Reporter: Paul Rogers
> Assignee: Paul Rogers
> Priority: Major
> Fix For: 1.16.0
>
>
> The recently added schema framework enforces schema constraints at the table
> level. We now wish to add additional constraints at the column level.
> * If a column is marked as "strict", then the reader will use the exact type
> and mode from the column schema, or fail if it is not possible to do so.
> * If a column is marked as required, and provides a default value, then that
> value is used instead of 0 if a row is missing a value for that column.
> This PR may also contain other fixes the the base functional revealed through
> additional testing.
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