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https://issues.apache.org/jira/browse/CARBONDATA-458?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15703060#comment-15703060
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Jihong MA commented on CARBONDATA-458:
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this work will contain materializing all file footer into a central file？please
describe where this file will be stored under which directory? in what
granularity(meaning would it allows blocklet level or file level filtering at
the driver side)?
> 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
>
> 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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