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From "Ning Zhang (JIRA)" <>
Subject [jira] Commented: (HIVE-1362) column level statistics
Date Fri, 21 May 2010 23:36:16 GMT


Ning Zhang commented on HIVE-1362:

This is the 2nd subtask of HIVE-33 (stats in Hive tables). 

We will gather column level stats based on users' request. It also depends on HIVE-1361 in
that the metastore API should suport storing and retrieving stats. 

The major milestone for this subtasks are:
 1) add a new HiveQL command to gather column level stats. Please see HIVE-33 for the syntax.

 2) add new UDFs/UDAFs to compute these statistics. 

The proposed statistics are:
  - number of distinct values
  - number of NULL values
  - min/max k values where k could be given by user
  - histogram: frequency and height balanced
  - average size of the column
  - avg/sum of all values in the column if their type is numerical
  - percentiles of the value

> column level statistics
> -----------------------
>                 Key: HIVE-1362
>                 URL:
>             Project: Hadoop Hive
>          Issue Type: Sub-task
>            Reporter: Ning Zhang
>            Assignee: Ahmed M Aly

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