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From mohammadshahidkhan <>
Subject [GitHub] incubator-carbondata pull request #454: [CARBONDATA-484] Implement LRU cache...
Date Thu, 22 Dec 2016 19:58:19 GMT
GitHub user mohammadshahidkhan opened a pull request:

    [CARBONDATA-484] Implement LRU cache for B-Tree

    LRU Cache for B-Tree is proposed to ensure to avoid out memory, when too many number of
tables exits and all are not frequently used.
    CarbonData is maintaining two level of B-Tree cache, one at the driver level and another
at executor level. Currently CarbonData has the mechanism to invalidate the segments and blocks
cache for the invalid table segments, but there is no eviction policy for the unused cached
object. So the instance at which complete memory is utilized then the system will not be able
to process any new requests.
    In the cache maintained at the driver level and at the executor there must be objects
in cache currently not in use. Therefore system should have the mechanism to below mechanism.
    1. Set the max memory limit till which objects could be hold in the memory.
    2. When configured memory limit reached then identify the cached objects currently not
in use so that the required memory could be freed without impacting the existing process.
    3. Eviction should be done only till the required memory is not meet.
    4. Compacted segments driver and executor cache should be invalidated 
    ## Below things are as part of this PR:
    1. Implemented Block B-Tree LRU cache at the executor side.
    2. Implemented Segment B-Tree LRU cache at Driver side.
    3. Implemented mechanism to clear the compacted segment cache from the segment cache.
    4. Implemented mechanism to clear to blocks from the executor cache.

You can merge this pull request into a Git repository by running:

    $ git pull LRU_Cache_ForB-Tree

Alternatively you can review and apply these changes as the patch at:

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #454
commit 2455544b6cd710d4fef6494e41739529b1c6b3df
Author: mohammadshahidkhan <>
Date:   2016-10-05T04:45:09Z

    [CARBONDATA-484] Implement LRU cache for B-Tree


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