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From "Tor Myklebust (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SPARK-5472) Add support for reading from and writing to a JDBC database
Date Tue, 03 Feb 2015 20:51:36 GMT

    [ https://issues.apache.org/jira/browse/SPARK-5472?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14303961#comment-14303961
] 

Tor Myklebust commented on SPARK-5472:
--------------------------------------

It probably does not handle SQL ARRAY types in a sane way.  I would guess that type mapping
would throw an error if you try to read from a table that has an ARRAY column.  I would also
guess that type mapping would throw an error if you try to write a DataFrame that has an ARRAY
column.

JDBCRDD handles partitioning however you instruct it to.  If you give no instructions, the
entire table is a single partition.  If you give it a JDBCPartitioningInfo object, it divides
the specified range of the specified column into the appropriate number of slices.  If you
give it a list of WHERE clauses, each WHERE clause corresponds to one partition.

> Add support for reading from and writing to a JDBC database
> -----------------------------------------------------------
>
>                 Key: SPARK-5472
>                 URL: https://issues.apache.org/jira/browse/SPARK-5472
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Tor Myklebust
>            Assignee: Tor Myklebust
>            Priority: Blocker
>             Fix For: 1.3.0
>
>
> It would be nice to be able to make a table in a JDBC database appear as a table in Spark
SQL.  This would let users, for instance, perform a JOIN between a DataFrame in Spark SQL
with a table in a Postgres database.
> It might also be nice to be able to go the other direction -- save a DataFrame to a database
-- for instance in an ETL job.
> Edited to clarify:  Both of these tasks are certainly possible to accomplish at the moment
with a little bit of ad-hoc glue code.  However, there is no fundamental reason why the user
should need to supply the table schema and some code for pulling data out of a ResultSet row
into a Catalyst Row structure when this information can be derived from the schema of the
database table itself.



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