Ajantha Bhat created CARBONDATA-3118:
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Summary: Parallelize block pruning of default datamap in driver for filter query processing
Key: CARBONDATA-3118
URL:
https://issues.apache.org/jira/browse/CARBONDATA-3118 Project: CarbonData
Issue Type: Improvement
Reporter: Ajantha Bhat
Assignee: Ajantha Bhat
*"Parallelize block pruning of default datamap in driver
for filter query processing"*
*Background:*
We do block pruning for the filter queries at the driver side.
In real time big data scenario, we can have millions of carbon files for
one carbon table.
It is currently observed that for 1 million carbon files it takes around 5
seconds for block pruning. As each carbon file takes around 0.005ms for
pruning
(with only one filter columns set in 'column_meta_cache' tblproperty).
If the files are more, we might take more time for block pruning.
Also, spark Job will not be launched until block pruning is completed. so,
the user will not know what is happening at that time and why spark job is
not launching.
currently, block pruning is taking time as each segment processing is
happening sequentially. we can reduce the time by parallelizing it.
*solution:*Keep default number of threads for block pruning as 4.
User can reduce this number by a carbon property
"carbon.max.driver.threads.for.pruning" to set between -> 1 to 4.
In TableDataMap.prune(),
group the segments as per the threads by distributing equal carbon files to
each thread.
Launch the threads for a group of segments to handle block pruning.
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