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https://issues.apache.org/jira/browse/CARBONDATA-458?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jacky Li resolved CARBONDATA-458.
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Resolution: Fixed
Fix Version/s: 0.3.0-incubating
> Improving carbon first time query performance
> ----------------------------------------------
>
> Key: CARBONDATA-458
> URL: https://issues.apache.org/jira/browse/CARBONDATA-458
> Project: CarbonData
> Issue Type: Improvement
> Components: core, data-load, data-query
> Reporter: kumar vishal
> Assignee: kumar vishal
> Fix For: 0.3.0-incubating
>
> Time Spent: 4.5h
> Remaining Estimate: 0h
>
> Improving carbon first time query performance
> Reason:
> 1. As file system cache is cleared file reading will make it slower to read
> and cache
> 2. In first time query carbon will have to read the footer from file data
> file to form the btree
> 3. Carbon reading more footer data than its required(data chunk)
> 4. There are lots of random seek is happening in carbon as column data(data
> page, rle, inverted index) are not stored together.
> Solution:
> 1. Improve block loading time. This can be done by removing data chunk from
> blockletInfo and storing only offset and length of data chunk
> 2. compress presence meta bitset stored for null values for measure column
> using snappy
> 3. Store the metadata and data of a column together and read together this
> reduces random seek and improve IO
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