xuchuanyin created CARBONDATA-1335:
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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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