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https://issues.apache.org/jira/browse/HAWQ-492?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15206831#comment-15206831
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Goden Yao commented on HAWQ-492:
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I see. I think what you need is to return Partial content of a record - in
other words, return the columns in the SELECT query only.
This is only achievable with columnar storage format (e.g. parquet or ORC) not
for text, sequence , etc.
So this implementation depends on specific plugin implementation. (e.g. if we
have a parquet plugin for PXF, this plugin can implement this logic.)
We don't have these JIRAs filed yet but we certainly welcome ideas like this
and hope you and others may help to contribute.
> PXF Query Push-Down Feature enhancement to enable further push down to
> Datasource
> ---------------------------------------------------------------------------------
>
> Key: HAWQ-492
> URL: https://issues.apache.org/jira/browse/HAWQ-492
> Project: Apache HAWQ
> Issue Type: Improvement
> Components: PXF
> Reporter: Michael Andre Pearce (IG)
> Assignee: Lei Chang
>
> PXF currently supports push down of filters to the PXF plugin. So that PXF
> itself only needs to return the fields and rows that match the filters.
> Unfortunately it seems (and it could be simply miss-understanding) is done in
> a way where by the PXF plugin must retrieve the complete row/entry from the
> source then the filters are applied. With Query Filter Push-Down feature.
> With a JDBC PXF (https://github.com/kojec/pxf-field/tree/master/jdbc-pxf-ext)
> this seems to be the case where by the SELECT * FROM table is done.
> It would be much more efficient if the filter and fields are push down in a
> way so that the plugin can if in its use case can actually delegate that
> further down into datasource it is using, and retrieving and applying the
> filters needed to reduce the data it needs to be pulled back.
> As such the PXF accessor would be able to construct SELECT fieldA fieldB FROM
> table WHERE fieldA > 6
> It maybe that this is indeed possible, but looking at
> https://github.com/kojec/pxf-field/tree/master/jdbc-pxf-ext and the API's and
> documents currently available we cannot see a way to improve this jdbc pxf
> plugin to achieve this.
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