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https://issues.apache.org/jira/browse/HIVE-18743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16385374#comment-16385374
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Alexander Kolbasov commented on HIVE-18743:
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[~kgyrtkirk] what is the value of high-value qtest? The unit test allows me to
control execution environment of the function exactly and it gives me an
opportunity to verify whether warehouse ops are called or not. What extra value
would we get from a qtest that we don't get from unit test?
> 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-18743.06.patch, HIVE-18743.07.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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