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From sujith71955 <...@git.apache.org>
Subject [GitHub] incubator-carbondata pull request #423: [CARBONDATA-527] Greater than/less-t...
Date Mon, 12 Dec 2016 18:23:09 GMT
GitHub user sujith71955 opened a pull request:

    https://github.com/apache/incubator-carbondata/pull/423

    [CARBONDATA-527] Greater than/less-than/Like filters optimization for dictionary columns

    Current design 
    In greater than/less-than/Like filters, system first iterates each row present in the
dictionary cache for identifying valid filter actual members  by applying the filter expression
, once evaluation done system will hold the list of identified valid filter actual member
values(String), now in next step again  system will look up the dictionary cache in order
to identify the dictionary surrogate values of the identified members. this look up is an
additional cost to our system even though the look up methodology is an binary search in dictionary
cache.
     
    Proposed design/solution:
    Identify the dictionary surrogate values in filter expression evaluation step itself 
when actual dictionary values will be scanned for identifying valid filter members .
    
    Keep a dictionary counter variable which will be increased  when system iterates through
 the dictionary cache in order to retrieve each actual member stored in dictionary cache ,
after this system will evaluate each row against the filter expression to identify whether
its a valid filter member or not, while doing this process itself counter value can be taken
as valid selected dictionary value since the actual member values and its  dictionary values
will be kept in same order in dictionary cache as the iteration order.
    
    thus it will eliminate the further dictionary look up step which is required  to retrieve
the dictionary surrogate value against identified actual valid filter member. this can also
increase significantly the filter query performance of such filter queries which require expression
evaluation to identify it the filter members by looking up dictionary cache, like greater
than/less-than/Like filters .
    
    Note : this optimization is applicable for dictionary columns.


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

    $ git pull https://github.com/sujith71955/incubator-carbondata master_likefilter

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

    https://github.com/apache/incubator-carbondata/pull/423.patch

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

    This closes #423
    
----
commit b81b4aaa58ca9de79b8b3cdf3191a7fa0f14575a
Author: sujith71955 <sujithchacko.2010@gmail.com>
Date:   2016-12-12T18:23:38Z

    JIRA ID: CARBONDATA-527
    Description:
    Identify the dictionary surrogate values in filter expression evaluation step itself 
when actual dictionary values will be scanned for identifying valid filter members

----


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