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https://issues.apache.org/jira/browse/DRILL-4694?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15315196#comment-15315196
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ASF GitHub Bot commented on DRILL-4694:
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GitHub user parthchandra opened a pull request:
https://github.com/apache/drill/pull/514
DRILL-4694: CTAS in JSON format produces extraneous NULL fields
Changed behavior of JSON CTAS to skip fields if the value is null. Added
an option "store.json.writer.skip_null_fields" to enable old behavior.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/parthchandra/drill DRILL-4694
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/drill/pull/514.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #514
----
commit 68ff4950f8302725aadf72a50074f6eef735738b
Author: Parth Chandra <[email protected]>
Date: 2016-06-02T00:19:03Z
DRILL-4694: CTAS in JSON format produces extraneous NULL fields
Changed behavior of JSON CTAS to skip fields if the value is null. Added
an option "store.json.writer.skip_null_fields" to enable old behavior.
----
> CTAS in JSON format produces extraneous NULL fields
> ---------------------------------------------------
>
> Key: DRILL-4694
> URL: https://issues.apache.org/jira/browse/DRILL-4694
> Project: Apache Drill
> Issue Type: Bug
> Components: Storage - JSON
> Affects Versions: 1.6.0
> Reporter: Aman Sinha
>
> Consider the following JSON file:
> {noformat}
> // file t2.json
> {
> "X" : {
> "key1" : "value1",
> "key2" : "value2"
> }
> }
> {
> "X" : {
> "key3" : "value3",
> "key4" : "value4"
> }
> }
> {
> "X" : {
> "key5" : "value5",
> "key6" : "value6"
> }
> }
> {noformat}
> Now create a table in Json format using CTAS:
> {noformat}
> 0: jdbc:drill:zk=local> alter session set `store.format` = 'json';
> 0: jdbc:drill:zk=local> create table dfs.tmp.jt12 as select t.`X` from
> `t2.json` t;
> +-----------+----------------------------+
> | Fragment | Number of records written |
> +-----------+----------------------------+
> | 0_0 | 3 |
> +-----------+----------------------------+
> {noformat}
> The output file has rows with union schema of all the fields in all the
> records. This creates extraneous Null fields in the output:
> {noformat}
> $ cat jt12/0_0_0.json
> {
> "X" : {
> "key1" : "value1",
> "key2" : "value2",
> "key3" : null,
> "key4" : null,
> "key5" : null,
> "key6" : null
> }
> } {
> "X" : {
> "key1" : null,
> "key2" : null,
> "key3" : "value3",
> "key4" : "value4",
> "key5" : null,
> "key6" : null
> }
> } {
> "X" : {
> "key1" : null,
> "key2" : null,
> "key3" : null,
> "key4" : null,
> "key5" : "value5",
> "key6" : "value6"
> }
> }
> {noformat}
> Note that if I change the output format to CSV or Parquet, there are no Null
> fields created in the output file. The expectation for a CTAS in json
> format is that the output should match that of the input json data.
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