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https://issues.apache.org/jira/browse/HAWQ-927?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15385261#comment-15385261
]
ASF GitHub Bot commented on HAWQ-927:
-------------------------------------
Github user xunzhang commented on a diff in the pull request:
https://github.com/apache/incubator-hawq/pull/796#discussion_r71461014
--- 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 --
@kavinderd What' the code logic of PXF end to parse this header? Does it be
included in another pull request?
> 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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