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https://issues.apache.org/jira/browse/HIVE-11625?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14708885#comment-14708885
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Cheng Lian commented on HIVE-11625:
-----------------------------------
I meant to open this issue as a Parquet bug, but it seems that the Parquet
support in Hive code base diverges a lot from parquet-hive. Fixes made in Hive
were not backported to parquet-hive. For example, [the most recent master
version of
parquet-hive|https://github.com/apache/parquet-mr/blob/04f524d5ad91b1cdda66dfde4089f2f83f4528aa/parquet-hive/parquet-hive-storage-handler/src/main/java/org/apache/hadoop/hive/ql/io/parquet/write/DataWritableWriter.java]
doesn't support writing maps, decimals, or timestamps, while all these data
types are [supported in Hive
1.2.1|https://github.com/apache/hive/blob/release-1.2.1/ql/src/java/org/apache/hadoop/hive/ql/io/parquet/write/DataWritableWriter.java#L223-L237]
and earlier versions.
> Map instances with null keys are not written to Parquet tables
> --------------------------------------------------------------
>
> Key: HIVE-11625
> URL: https://issues.apache.org/jira/browse/HIVE-11625
> Project: Hive
> Issue Type: Bug
> Affects Versions: 0.14.0, 0.13.1, 1.0.1, 1.1.1, 1.2.1
> Reporter: Cheng Lian
>
> Hive allows maps with null keys:
> {code:sql}
> hive> select map(null, 'foo', 1, 'bar', null, 'baz');
> {null:"baz",1:"bar"}
> {code}
> However, when written into Parquet tables, map entries with null as keys are
> dropped:
> {code:sql}
> hive> CREATE TABLE map_test STORED AS PARQUET
> > AS SELECT MAP(null, 'foo', 1, 'bar', null, 'baz');
> ...
> hive> SELECT * from map_test;
> {1:"bar"}
> {code}
> This is because entries with null keys are explicitly skipped in
> {{DataWritableWriter}}, [see
> here|https://github.com/apache/hive/blob/release-1.2.1/ql/src/java/org/apache/hadoop/hive/ql/io/parquet/write/DataWritableWriter.java#L223-L237].
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