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From "Yibing Shi (JIRA)" <>
Subject [jira] [Commented] (HIVE-15530) Optimize the column stats update logic in table alteration
Date Tue, 10 Jan 2017 12:06:58 GMT


Yibing Shi commented on HIVE-15530:

You are right that the column stats don't need to be updated if only column positions are
changed. Current patch doesn't optimize this, because I didn't notice that {{areSameColumns}}
also compares column positions. I will upload a new patch soon.

> Optimize the column stats update logic in table alteration
> ----------------------------------------------------------
>                 Key: HIVE-15530
>                 URL:
>             Project: Hive
>          Issue Type: Bug
>          Components: Hive
>            Reporter: Yibing Shi
>            Assignee: Yibing Shi
>         Attachments: HIVE-15530.1.patch, HIVE-15530.2.patch, HIVE-15530.3.patch, HIVE-15530.4.patch
> Currently when a table is altered, if any of below conditions is true, HMS would try
to update column statistics for the table:
> # database name is changed
> # table name is changed
> # old columns and new columns are not the same
> As a result, when a column is added to a table, Hive also tries to update column statistics,
which is not necessary. We can loose the last condition by checking whether all existing columns
are changed or not. If not, we don't have to update stats info.

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