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https://issues.apache.org/jira/browse/DRILL-4479?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15190386#comment-15190386
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Aman Sinha commented on DRILL-4479:
-----------------------------------
I have updated the PR: https://github.com/apache/drill/pull/420
This contains additional fix to avoid schema change issues when doing group-by
(or some other operation) under all_text_mode as I had described in prior
comment. Added appropriate tests.
[~hgunes] could you please review ? Thanks.
> JsonReader should pick a less restrictive type when creating the default
> column
> -------------------------------------------------------------------------------
>
> Key: DRILL-4479
> URL: https://issues.apache.org/jira/browse/DRILL-4479
> Project: Apache Drill
> Issue Type: Bug
> Components: Storage - JSON
> Affects Versions: 1.5.0
> Reporter: Aman Sinha
> Assignee: Aman Sinha
> Fix For: 1.7.0
>
> Attachments: mostlynulls.json
>
>
> This JIRA is related to DRILL-3806 but has a narrower scope, so I decided to
> create separate one.
> The JsonReader has the method ensureAtLeastOneField() (see
> https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/vector/complex/fn/JsonReader.java#L91)
> that ensures that when no columns are found, create an empty one and it
> chooses to create a nullable int column. One consequence is that queries of
> the following type fail:
> {noformat}
> select c1 from dfs.`mostlynulls.json`;
> ...
> ...
> | null |
> | null |
> Error: DATA_READ ERROR: Error parsing JSON - You tried to write a VarChar
> type when you are using a ValueWriter of type NullableIntWriterImpl.
> File /Users/asinha/data/mostlynulls.json
> Record 4097
> {noformat}
> In this file the first 4096 rows have NULL values for c1 followed by rows
> that have a valid string.
> It would be useful for the Json reader to choose a less restrictive type such
> as varchar in order to allow more types of queries to run.
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