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https://issues.apache.org/jira/browse/HAWQ-927?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15386155#comment-15386155
 ] 

ASF GitHub Bot commented on HAWQ-927:
-------------------------------------

Github user kavinderd commented on a diff in the pull request:

    https://github.com/apache/incubator-hawq/pull/796#discussion_r71559534
  
    --- Diff: src/backend/access/external/pxfheaders.c ---
    @@ -158,6 +166,29 @@ static void add_tuple_desc_httpheader(CHURL_HEADERS 
headers, Relation rel)
        pfree(formatter.data);
     }
     
    +static void add_projection_desc_httpheader(CHURL_HEADERS headers, 
ProjectionInfo *projInfo) {
    +   int i;
    +   char long_number[sizeof(int32) * 8];
    +   int *varNumbers = projInfo->pi_varNumbers;
    +   StringInfoData formatter;
    +   initStringInfo(&formatter);
    +
    +    /* Convert the number of projection columns to a string */
    +    pg_ltoa(list_length(projInfo->pi_targetlist), long_number);
    +    churl_headers_append(headers, "X-GP-ATTRS-PROJ", long_number);
    +
    +   for(i = 0; i < list_length(projInfo->pi_targetlist); i++) {
    --- End diff --
    
    Yes it will be in another PR related to 
[this](https://issues.apache.org/jira/browse/HAWQ-583?jql=project%20%3D%20HAWQ%20AND%20resolution%20%3D%20Unresolved%20AND%20assignee%20%3D%20kavinderd%20ORDER%20BY%20priority%20DESC)
 Jira.


> 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.



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