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From "Zoltan Haindrich (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-18743) CREATE TABLE on S3 data can be extremely slow. DO_NOT_UPDATE_STATS workaround is buggy.
Date Thu, 22 Feb 2018 06:25:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-18743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16372465#comment-16372465
] 

Zoltan Haindrich commented on HIVE-18743:
-----------------------------------------

are there any reason you decided not to remove this thing?

> CREATE TABLE on S3 data can be extremely slow. DO_NOT_UPDATE_STATS workaround is buggy.
> ---------------------------------------------------------------------------------------
>
>                 Key: HIVE-18743
>                 URL: https://issues.apache.org/jira/browse/HIVE-18743
>             Project: Hive
>          Issue Type: Improvement
>          Components: Metastore
>    Affects Versions: 1.2.0, 1.1.0, 2.0.2, 3.0.0
>            Reporter: Alexander Behm
>            Assignee: Alexander Kolbasov
>            Priority: Major
>         Attachments: HIVE-18743.01.patch, HIVE-18743.02.patch, HIVE-18743.03.patch
>
>
> When hive.stats.autogather=true then the Metastore lists all files under the table directory
to populate basic stats like file counts and sizes. This file listing operation can be very
expensive particularly on filesystems like S3.
> One way to address this issue is to reconfigure hive.stats.autogather=false.
> *Here's the bug*
> It is my understanding that the DO_NOT_UPDATE_STATS table property is intended to selectively
prevent this stats collection. Unfortunately, this table property is checked *after* the expensive
file listing operation, so the DO_NOT_UPDATE_STATS does not seem to work as intended. See:
> https://github.com/apache/hive/blob/master/standalone-metastore/src/main/java/org/apache/hadoop/hive/metastore/utils/MetaStoreUtils.java#L633
> Relevant code snippet:
> {code}
>   public static boolean updateTableStatsFast(Database db, Table tbl, Warehouse wh,
>                                              boolean madeDir, boolean forceRecompute,
EnvironmentContext environmentContext) throws MetaException {
>     if (tbl.getPartitionKeysSize() == 0) {
>       // Update stats only when unpartitioned
>       FileStatus[] fileStatuses = wh.getFileStatusesForUnpartitionedTable(db, tbl);
>       return updateTableStatsFast(tbl, fileStatuses, madeDir, forceRecompute, environmentContext);
<--- DO_NOT_UPDATE_STATS is checked in here after wh.getFileStatusesForUnpartitionedTable()
has already been called
>     } else {
>       return false;
>     }
>   }
> {code}



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