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From "Lisen Mu (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DRILL-60) multiple query support
Date Mon, 13 May 2013 08:21:15 GMT
Lisen Mu created DRILL-60:
-----------------------------

             Summary: multiple query support
                 Key: DRILL-60
                 URL: https://issues.apache.org/jira/browse/DRILL-60
             Project: Apache Drill
          Issue Type: New Feature
            Reporter: Lisen Mu


parse/optimize several SQL(or other QL)s into one logical plan and execute them once.
 
* use case
If a report generating system is used as a frontend system of drill instead of a command line,
There would be a set of similar SQL to execute to generate a report(consider each day's DAU
statistics with geoip distribution(groupby) for 7 continuous days). If processed individually,
plans for SQLs in this kind of set are similar(scan pv log in these days) or same(scan GeoIP
table) in majority. If processed together, duplicated scan(GeoIP) could be eliminated to reduce
I/O, or similar scan(pv) could be merged to achieve better throughput, and provides chances
of other intermediate result reuse.

* possibility
Query in a QL is represented as a tree. Drill models logical plan and physical plan as DAG,
which is more expressive than tree. More precisely, a set of trees(with common nodes or common
edges) can be union-ed into a dag. So, the current drill logical/physical plan model supports
multiple query already. Each sql would have a corresponding StoreOP as its result.

* problems
To do so, physical operators must support multiple iteration over its output. That would have
side effect on mem management.


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