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https://issues.apache.org/jira/browse/HIVE-7446?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14089885#comment-14089885
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Ashish Kumar Singh commented on HIVE-7446:
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[~szehon] thanks for your valuable insight here. This helped me discover that
as of now alter table is actually not working for avro backed tables in Hive.
Alter table updates HMS with new schema, but schema in the avro file containing
avro-backed table's data keeps the original schema. On trying to read from the
avro-backed table after altering table, avro throws exception while trying to
read the avro file. This exception is thrown because of difference in expected
and actual schemas.
Based on offline discussion with [~tomwhite], Avro allows files written with
the old schema to be read with the new schema as long as certain rules are
followed, e.g. adding a new field has a default value. The full set of rules
are at http://avro.apache.org/docs/current/spec.html#Schema+Resolution.
I will upload a patch that should fix this with appropriate tests.
> Add support to ALTER TABLE .. ADD COLUMN to Avro backed tables
> --------------------------------------------------------------
>
> Key: HIVE-7446
> URL: https://issues.apache.org/jira/browse/HIVE-7446
> Project: Hive
> Issue Type: New Feature
> Reporter: Ashish Kumar Singh
> Assignee: Ashish Kumar Singh
> Attachments: HIVE-7446.patch
>
>
> HIVE-6806 adds native support for creating hive table stored as Avro. It
> would be good to add support to ALTER TABLE .. ADD COLUMN to Avro backed
> tables.
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