Lisen Mu created DRILL-60:
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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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