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https://issues.apache.org/jira/browse/HIVE-2928?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13250361#comment-13250361
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Carl Steinbach commented on HIVE-2928:
--------------------------------------
@Mithun: What happens on MySQL if you turn column validation on (e.g.
datanucleus.validateColumns=true at startup)? There's a note on the Datanucleus
site that indicates this won't work:
http://www.datanucleus.org/products/datanucleus/rdbms/support.html
{quote}
You can specify "BLOB", "CLOB" JDBC types when using MySQL with DataNucleus but
you must turn validation of columns OFF. This is because these types are not
supported by the MySQL JDBC driver and it returns them as
LONGVARBINARY/LONGVARCHAR when querying the column type.
{quote}
> Support for Oracle-backed Hive-Metastore ("longvarchar" to "clob" in
> package.jdo)
> ---------------------------------------------------------------------------------
>
> Key: HIVE-2928
> URL: https://issues.apache.org/jira/browse/HIVE-2928
> Project: Hive
> Issue Type: New Feature
> Components: Metastore
> Affects Versions: 0.9.0
> Reporter: Mithun Radhakrishnan
> Attachments: HIVE-2928.patch
>
>
> I'm trying to get the Hive-Metastore to work when backed by an Oracle
> backend. There's a change to hive's package.jdo that I'd like advice/comments
> on.
> One sticking point on working with Oracle has been the TBLS table (MTable)
> and its 2 LONGVARCHAR properties (VIEW_ORIGINAL_TEXT and VIEW_EXPANDED_TEXT).
> Oracle doesn't support more than one LONGVARCHAR property per table (for
> reason of legacy), and prefers that one use CLOBs instead. If one switches to
> CLOB properties, with no modification to hive's package.jdo, one sees the
> following exception:
> <quote>
> Incompatible data type for column TBLS.VIEW_EXPANDED_TEXT : was CLOB
> (datastore), but type expected was LONGVARCHAR (metadata). Please check that
> the type in the datastore and the type specified in the MetaData are
> consistent.
> org.datanucleus.store.rdbms.exceptions.IncompatibleDataTypeException:
> Incompatible data type for column TBLS.VIEW_EXPANDED_TEXT : was CLOB
> (datastore), but type expected was LONGVARCHAR (metadata). Please check that
> the type in the datastore and the type specified in the MetaData are
> consistent.
> at
> org.datanucleus.store.rdbms.table.ColumnImpl.validate(ColumnImpl.java:521)
> at
> org.datanucleus.store.rdbms.table.TableImpl.validateColumns(TableImpl.java:2
> </quote>
> But if one rebuilds Hive with the package.jdo changed to use CLOBs instead of
> LONGVARCHARs, things look promising:
> 1. The exception no longer occurs. Things seem to work with Oracle. (I've yet
> to scale-test.)
> 2. These modified hive-libraries work as is with pre-existing mysql
> metastores. Migrating data isn't a worry.
> 3. The unit-tests seem to run through.
> Would there be opposition to changing the package.jdo's LONGVARCHAR
> references to CLOB, if this works with mysql and with Oracle?
> Mithun
> P.S. I also have a working hive-schema-0.9.0-oracle.sql script that I'm
> testing, for the related issue of creating the required tables in Oracle.
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