[jira] [Created] (FLINK-5752) Support push down projections for HBaseTableSource

["ramkrishna.s.vasudevan (JIRA)" <ji...@apache.org>]

ramkrishna.s.vasudevan created FLINK-5752:
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             Summary: Support push down projections for HBaseTableSource
                 Key: FLINK-5752
                 URL: https://issues.apache.org/jira/browse/FLINK-5752
             Project: Flink
          Issue Type: Sub-task
            Reporter: ramkrishna.s.vasudevan
            Assignee: ramkrishna.s.vasudevan


This is after the discussion to create NestedProjectableTableSource. 
Currently we support nested schema for the non-relational type of DBs like HBase. 
But this does not allow push down projection. This JIRA is to implement that. 
I just did a POC on the existing PR https://github.com/apache/flink/pull/3149.
The idea was to allow the family#quallifier to be specified in the query directly and parse the family and qualifier info and directly push down for projections.
I tried using fam$qual (with $) as separator but that had SQL parse error. Hence went with '_' as the separator and it worked. 
So now in order to maintain the order in which the projection has to be done we need to have a LinkedHashMap which has the qualifier to typeinfo mapping. This is because with f1_q1, f1_q2 as the schema, we could always project f1_q2 and the selection could be f1_q1. In that case the order of how the projection is done is very important so that there is no type mismatch. 
[~fhueske], [~tonycox], [~jark]



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