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Posted to dev@hive.apache.org by "Jesus Camacho Rodriguez (JIRA)" <ji...@apache.org> on 2016/06/15 16:19:09 UTC
[jira] [Created] (HIVE-14018) Make IN clause row selectivity
estimation customizable
Jesus Camacho Rodriguez created HIVE-14018:
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Summary: Make IN clause row selectivity estimation customizable
Key: HIVE-14018
URL: https://issues.apache.org/jira/browse/HIVE-14018
Project: Hive
Issue Type: Improvement
Components: Statistics
Affects Versions: 2.1.0, 2.2.0
Reporter: Jesus Camacho Rodriguez
Assignee: Jesus Camacho Rodriguez
Priority: Minor
After HIVE-13287 went in, we calculate IN clause estimates natively (instead of just dividing incoming number of rows by 2). However, as the distribution of values of the columns is considered uniform, we might end up heavily underestimating/overestimating the resulting number of rows.
This issue is to add a factor that multiplies the IN clause estimation so we can alleviate this problem. The solution is not very elegant, but it is the best we can do until we have histograms to improve our estimate.
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