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https://issues.apache.org/jira/browse/DERBY-6036?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13847533#comment-13847533
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Richard Huddleston commented on DERBY-6036:
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unfortunately we cannot use the foreign views / ForeignTableVTI as we are
writing our own adapter to greenplum.
we use derby as a front end to greenplum. we use derby to parse the sql and
then we submit the query to the greenplum master and instead of getting a
result in the jdbc connection, we do an ETL write to an external servlet which
is running in derby. ETLs in greenplum are VERY fast and prevent the bandwidth
crunch on the master greenplum node. In the ETL, EACH of our greenplum slaves
reaches out individually to the derby instance to post back result sets, and
does NOT use any resources on the master. Data gets pushed back to our derby
instance at greater than 1 gbit/sec, and our resultset merges the multiple http
posts back into a single result. People love our derby frontend to greenplum,
and now are thinking about other systems we should expose through derby. but
our system is not as fast as it could be.
> If you wrap a SELECT * view around a table, all of the columns are read from
> the base row even when you SELECT only a subset of the view columns.
> -------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-6036
> URL: https://issues.apache.org/jira/browse/DERBY-6036
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.10.1.1
> Reporter: Rick Hillegas
> Labels: derby_triage10_11
> Attachments: derby-6036-01-aa-testForRestrictionPushing.diff,
> derby-6036.sql, derbyAST.xml
>
>
> This also affects SELECTs from views wrapping RestrictedVTIs. Restrictions
> are pushed into a restricted VTI if you wrap it in a view. However,
> projections are not. I will attach a script showing this problem.
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