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https://issues.apache.org/jira/browse/HIVE-6131?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13945773#comment-13945773
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Pala M Muthaia commented on HIVE-6131:
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That thought did cross my mind. However, I wasn't sure if there are other
dependencies that actually need the table schema snapshot during partition
creation (which is stored as partition level schema).
A related question is why store partition specific column schema if it is
always identical to current table column schema? Then partition metadata should
not include column schema at all and always pick it up from table metadata.
I guess i am unsure about semantics of partition schema. Does it represent
current table schema, and if so, why we keep a copy separate from table schema.
If not, then it represents schema during partition creation, so it is possible
that it is out of date, leading to the inconsistency you describe.
> New columns after table alter result in null values despite data
> ----------------------------------------------------------------
>
> Key: HIVE-6131
> URL: https://issues.apache.org/jira/browse/HIVE-6131
> Project: Hive
> Issue Type: Bug
> Affects Versions: 0.11.0, 0.12.0, 0.13.0
> Reporter: James Vaughan
> Priority: Minor
> Attachments: HIVE-6131.1.patch.txt
>
>
> Hi folks,
> I found and verified a bug on our CDH 4.0.3 install of Hive when adding
> columns to tables with Partitions using 'REPLACE COLUMNS'. I dug through the
> Jira a little bit and didn't see anything for it so hopefully this isn't just
> noise on the radar.
> Basically, when you alter a table with partitions and then reupload data to
> that partition, it doesn't seem to recognize the extra data that actually
> exists in HDFS- as in, returns NULL values on the new column despite having
> the data and recognizing the new column in the metadata.
> Here's some steps to reproduce using a basic table:
> 1. Run this hive command: CREATE TABLE jvaughan_test (col1 string)
> partitioned by (day string);
> 2. Create a simple file on the system with a couple of entries, something
> like "hi" and "hi2" separated by newlines.
> 3. Run this hive command, pointing it at the file: LOAD DATA LOCAL INPATH
> '<FILEDIR>' OVERWRITE INTO TABLE jvaughan_test PARTITION (day = '2014-01-02');
> 4. Confirm the data with: SELECT * FROM jvaughan_test WHERE day =
> '2014-01-02';
> 5. Alter the column definitions: ALTER TABLE jvaughan_test REPLACE COLUMNS
> (col1 string, col2 string);
> 6. Edit your file and add a second column using the default separator
> (ctrl+v, then ctrl+a in Vim) and add two more entries, such as "hi3" on the
> first row and "hi4" on the second
> 7. Run step 3 again
> 8. Check the data again like in step 4
> For me, this is the results that get returned:
> hive> select * from jvaughan_test where day = '2014-01-01';
> OK
> hi NULL 2014-01-02
> hi2 NULL 2014-01-02
> This is despite the fact that there is data in the file stored by the
> partition in HDFS.
> Let me know if you need any other information. The only workaround for me
> currently is to drop partitions for any I'm replacing data in and THEN
> reupload the new data file.
> Thanks,
> -James
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