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https://issues.apache.org/jira/browse/HIVE-20006?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17601241#comment-17601241
]
comet commented on HIVE-20006:
------------------------------
apology, is MaterializationsCacheCleanerTask is replaced with another class on
Hive 3.1 onward? I would like to set below property, but class not found
```
<property>
<name>metastore.task.threads.always</name>
<value>org.apache.hadoop.hive.metastore.events.EventCleanerTask,org.apache.hadoop.hive.metastore.MaterializationsCacheCleanerTask</value>
</property>
```
> Make materializations invalidation cache work with multiple active remote
> metastores
> ------------------------------------------------------------------------------------
>
> Key: HIVE-20006
> URL: https://issues.apache.org/jira/browse/HIVE-20006
> Project: Hive
> Issue Type: Improvement
> Components: Materialized views
> Affects Versions: 3.0.0
> Reporter: Jesus Camacho Rodriguez
> Assignee: Jesus Camacho Rodriguez
> Priority: Critical
> Fix For: 4.0.0, 4.0.0-alpha-1
>
> Attachments: HIVE-19027.01.patch, HIVE-19027.02.patch,
> HIVE-19027.03.patch, HIVE-19027.04.patch, HIVE-20006.01.patch,
> HIVE-20006.02.patch, HIVE-20006.03.patch, HIVE-20006.04.patch,
> HIVE-20006.05.patch, HIVE-20006.06.patch, HIVE-20006.07.patch,
> HIVE-20006.patch
>
>
> The main points:
> - Only MVs that use transactional tables can have a time window value of 0.
> Those are the only MVs that can be guaranteed to not be outdated when a query
> is executed.
> - For MVs that +cannot be outdated+, comparison is based on valid write id
> lists.
> - For MVs that +can be outdated+:
> ** The window for valid outdated MVs can be specified in intervals of 1
> minute.
> ** A materialized view is outdated if it was built before that time window
> and any source table has been modified since.
> A time window of -1 means to always use the materialized view for rewriting
> without any checks concerning its validity. If a materialized view uses an
> external table, the only way to trigger the rewriting would be to set the
> property to -1, since currently we do not capture for validation purposes
> whether the external source tables have been modified since the MV was
> created or not.
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