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https://issues.apache.org/jira/browse/IMPALA-10723?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Work on IMPALA-10723 started by Aman Sinha.
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> Allow basic querying and computing stats on a materialized view
> ---------------------------------------------------------------
>
> Key: IMPALA-10723
> URL: https://issues.apache.org/jira/browse/IMPALA-10723
> Project: IMPALA
> Issue Type: Improvement
> Components: Frontend
> Reporter: Aman Sinha
> Assignee: Aman Sinha
> Priority: Major
>
> Currently, in Impala, a Materialized View (MV) created via Hive is visible
> through the metadata catalog and can be queried but the query is expanded to
> its corresponding view definition. This is incorrect because a materialized
> view is a regular (physical) table, not a view. Even though Impala does not
> support either creating MV or automatic rewriting to use MV, querying an MV
> directly should be allowed.
> Here's the current behavior:
> {noformat}
> [localhost:21050] functional> explain select * from materialized_view;
> Query: explain select * from materialized_view
> +------------------------------------------------------------------------------------+
> | Explain String
> |
> +------------------------------------------------------------------------------------+
> | Max Per-Host Resource Reservation: Memory=4.00MB Threads=2
> |
> | Per-Host Resource Estimates: Memory=10MB
> |
> | WARNING: The following tables are missing relevant table and/or column
> statistics. |
> | functional.insert_only_transactional_table
> |
> |
> |
> | PLAN-ROOT SINK
> |
> | |
> |
> | 01:EXCHANGE [UNPARTITIONED]
> |
> | |
> |
> | 00:SCAN HDFS [functional.insert_only_transactional_table]
> |
> | HDFS partitions=1/1 files=0 size=0B
> |
> | row-size=4B cardinality=0
> |
> +------------------------------------------------------------------------------------+
> {noformat}
> Note that the plan shows the scan of the underlying table instead of the
> materialized_view table. We should only be scanning the MV (including
> applying partition pruning, predicate pushdown etc.) and not treating this as
> a view.
> This JIRA is to enhance the frontend to recognize a materialized view as a
> table rather than a view. This will further allow commands such as COMPUTE
> STATS, DROP STATS, SHOW [TABLE | COLUMN] STATS to be run on the MV. One
> motivation for doing this is to allow an external frontend that supports
> automatic query rewrites using MVs to leverage the statistics on MVs.
> Since Impala is not creating the MV, we will need to block DML operations on
> the MV. Further, special handling needs to be done for Ranger authorization
> policies such that any column masking/row filtering policies defined on the
> source tables of the MV are taken into consideration.
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