[
https://issues.apache.org/jira/browse/HAWQ-927?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15382958#comment-15382958
]
Kavinder Dhaliwal commented on HAWQ-927:
----------------------------------------
My initial implementation of this feature is to introduce a struct in the HAWQ
codebase {{ExternalSelectDescData}} that currently holds a pointer to the
current queries {{ProjectionInfo}} struct. I chose to pass the pointer through
the encapsulating struct because I believe this will make it more convenient to
pack more data into the struct to give PXF more insight into aspects of a query
(aggregate functions, filters, limits).
To send the data to HAWQ via the REST protocol I added "X-GP-PROJECT" and
"X-GP-PROJECT-COLS" to pass a flag whether there are any columns to project and
a list of those columns into the header data passed via the API request.
I look forward to the community's suggestions and feedback about this feature
> Send Projection Info Data from HAWQ to PXF
> ------------------------------------------
>
> Key: HAWQ-927
> URL: https://issues.apache.org/jira/browse/HAWQ-927
> Project: Apache HAWQ
> Issue Type: Sub-task
> Components: External Tables, PXF
> Reporter: Kavinder Dhaliwal
> Assignee: Kavinder Dhaliwal
> Fix For: backlog
>
>
> To achieve column projection at the level of PXF or the underlying readers we
> need to first send this data as a Header/Param to PXF. Currently, PXF has no
> knowledge whether a query requires all columns or a subset of columns.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
