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https://issues.apache.org/jira/browse/TAJO-838?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14164613#comment-14164613
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ASF GitHub Bot commented on TAJO-838:
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Github user jihoonson commented on the pull request:
https://github.com/apache/tajo/pull/192#issuecomment-58456061
Hi Hyunsik, thanks for your comment.
The index size is 2.4 GB while the size of input table is 41 GB. As you
commented, the index size is quite large, because the index is built for only
one column.
Furthermore, I used a straight forward approach to utilize the current bst
index implementation. That is, multiple bst indexes are created for each hdfs
block, and stored in HDFS. This may cause remote accesses during index access.
After finishing this issue, we can discuss the required features related to
the next generation index structure.
Sincerely,
Jihoon
> Improve query planner to utilize index
> --------------------------------------
>
> Key: TAJO-838
> URL: https://issues.apache.org/jira/browse/TAJO-838
> Project: Tajo
> Issue Type: Sub-task
> Components: planner/optimizer
> Reporter: Jihoon Son
> Assignee: Jihoon Son
> Priority: Minor
>
> Index can improve the query performance when the selectivity of query is high.
> Thus, query planner should decide whether index is used or not for a given
> query.
> The selectivity can be guessed using statistics.
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