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From "xuchuanyin (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CARBONDATA-1335) Duplicated & time-consuming method call found in query
Date Thu, 27 Jul 2017 06:50:00 GMT
xuchuanyin created CARBONDATA-1335:
--------------------------------------

             Summary: Duplicated & time-consuming method call found in query
                 Key: CARBONDATA-1335
                 URL: https://issues.apache.org/jira/browse/CARBONDATA-1335
             Project: CarbonData
          Issue Type: Improvement
          Components: data-query
    Affects Versions: 1.1.1
            Reporter: xuchuanyin
            Priority: Minor


# Scenario

Currently we did a concurrent  14 queries on Carbondata. The queries are the same, but on
different tables. We have noticed the following scene:

+ A single query took about 5s;
+ In concurrent scenario, each query took about 15s;

By adding checkpoint in the log, we found that there was great latency in starting query jobs
in spark.

# Analysts

When we fire a query, Carbondata firstly do some job in the client side, including parse/analyze
plans and prepare filtered blocks and inputSplits. Then Carbondata start to submit query job
to spark. 

We found in the first step, Carbondata took about 7s in current scenario, but it only took
about <1s in single scenario.
By studying the related code, we found the most time consuming method call was  `CarbonSessionCatalog.lookupRelation`.
In side this method, it called `super.lookupRelation` twice, which consumed about 3s each
time.

# Solution

Carbondata only needs to call the `super.lookupRelation` only once, we need to remove the
useless duplicated method call.

I've tested in my environment and it works well. In concurrent scenario, each query takes
about 12s (3s saved for the improvement).



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