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From "Vihang Karajgaonkar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-15995) Syncing metastore table with serde schema
Date Wed, 07 Mar 2018 18:25:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-15995?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16389925#comment-16389925
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Vihang Karajgaonkar commented on HIVE-15995:
--------------------------------------------

Hi [~szita] thanks for the updated patch. I was looking at the other queries which take in
{{cascade}} option and I noticed that they have a partition spec in the query syntax. Eg:
add/rename column is under alterTblPartitionStatementSuffix in HiveParser.g I think it has
to do with the option of adding partition spec to the command. Do you think it makes sense
to add a optional partition spec as well similar to add/replace columns query? I think column
descriptors are also at partition level. Eg. you can do a {{describe table foo partition (p1=10);}}
and hive will show the column information for that partition. So users can potentially update
the columns at a partition level as well. The current patch is either just the table no partitions
or table with all partitions. There is no way to update columns for a subset of partitions.

Also, in the qtest can you add a test for a partitioned table? Include describe table .. partition
.. syntax to confirm that partition columns are also getting updated.

> Syncing metastore table with serde schema
> -----------------------------------------
>
>                 Key: HIVE-15995
>                 URL: https://issues.apache.org/jira/browse/HIVE-15995
>             Project: Hive
>          Issue Type: Bug
>          Components: Metastore
>    Affects Versions: 1.2.1, 2.1.0, 3.0.0
>            Reporter: Michal Ferlinski
>            Assignee: Adam Szita
>            Priority: Major
>         Attachments: HIVE-15995.1.patch, HIVE-15995.2.patch, HIVE-15995.3.patch, HIVE-15995.4.patch,
HIVE-15995.patch, cx1.avsc, cx2.avsc
>
>
> Hive enables table schema evolution via properties. For avro e.g. we can alter the 'avro.schema.url'
property to update table schema to the next version. Updating properties however doesn't affect
column list stored in metastore DB so the table is not in the newest version when returned
from metastore API. This is problem for tools working with metastore (e.g. Presto).
> To solve this issue I suggest to introduce new DDL statement syncing metastore columns
with those from serde:
> {code}
> ALTER TABLE user_test1 UPDATE COLUMNS
> {code}
> Note that this is format independent solution. 
> To reproduce, follow the instructions below:
> - Create table based on avro schema version 1 (cxv1.avsc)
> {code}
> CREATE EXTERNAL TABLE user_test1
>   PARTITIONED BY (dt string)
>   ROW FORMAT SERDE
>   'org.apache.hadoop.hive.serde2.avro.AvroSerDe'
>   STORED AS INPUTFORMAT
>   'org.apache.hadoop.hive.ql.io.avro.AvroContainerInputFormat'
>   OUTPUTFORMAT
>   'org.apache.hadoop.hive.ql.io.avro.AvroContainerOutputFormat'
>   LOCATION
>   '/tmp/schema-evolution/user_test1'
>   TBLPROPERTIES ('avro.schema.url'='/tmp/schema-evolution/cx1.avsc');
> {code}
> - Update schema to version 2 (cx2.avsc)
> {code}
> ALTER TABLE user_test1 SET TBLPROPERTIES ('avro.schema.url' = '/tmp/schema-evolution/cx2.avsc');
> {code}
> - Print serde columns (top info) and metastore columns (Detailed Table Information):
> {code}
> DESCRIBE EXTENDED user_test1
> {code}



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