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https://issues.apache.org/jira/browse/DRILL-540?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16808496#comment-16808496
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Igor Guzenko commented on DRILL-540:
------------------------------------
Hi [~bbevens],
I think adding the warning is useful, except the last sentence 'For current
example views were defined as selection over appropriate tables'. Actually, for
*Storage Based Authorization* it impacts only show tables query. Like I shown
in comparison table, all views will be returned as a result. Because we don't
know permissions until user tries to select the view, then view is expanded
(converted to query) and underlying tables used in query are validated for
permissions.
Thanks,
Igor
> Allow querying hive views in Drill
> ----------------------------------
>
> Key: DRILL-540
> URL: https://issues.apache.org/jira/browse/DRILL-540
> Project: Apache Drill
> Issue Type: New Feature
> Components: Storage - Hive
> Reporter: Ramana Inukonda Nagaraj
> Assignee: Igor Guzenko
> Priority: Major
> Labels: doc-impacting, ready-to-commit
> Fix For: 1.16.0
>
>
> Currently hive views cannot be queried from drill.
> This Jira aims to add support for Hive views in Drill.
> *Implementation details:*
> # Drill persists it's views metadata in file with suffix .view.drill using
> json format. For example:
> {noformat}
> {
> "name" : "view_from_calcite_1_4",
> "sql" : "SELECT * FROM `cp`.`store.json`WHERE `store_id` = 0",
> "fields" : [ {
> "name" : "*",
> "type" : "ANY",
> "isNullable" : true
> } ],
> "workspaceSchemaPath" : [ "dfs", "tmp" ]
> }
> {noformat}
> Later Drill parses the metadata and uses it to treat view names in SQL as a
> subquery.
> 2. In Apache Hive metadata about views is stored in similar way to
> tables. Below is example from metastore.TBLS :
>
> {noformat}
> TBL_ID |CREATE_TIME |DB_ID |LAST_ACCESS_TIME |OWNER |RETENTION |SD_ID
> |TBL_NAME |TBL_TYPE |VIEW_EXPANDED_TEXT |
> -------|------------|------|-----------------|------|----------|------|----------|--------------|-------------------------------------------|
> 2 |1542111078 |1 |0 |mapr |0 |2 |cview
> |VIRTUAL_VIEW |SELECT COUNT(*) FROM `default`.`customers` |
> {noformat}
> 3. So in Hive metastore views are considered as tables of special type.
> And main benefit is that we also have expanded SQL definition of views (just
> like in view.drill files). Also reading of the metadata is already
> implemented in Drill with help of thrift Metastore API.
> 4. To enable querying of Hive views we'll reuse existing code for Drill
> views as much as possible. First in *_HiveSchemaFactory.getDrillTable_* for
> _*HiveReadEntry*_ we'll convert the metadata to instance of _*View*_ (_which
> is actually model for data persisted in .view.drill files_) and then based on
> this instance return new _*DrillViewTable*_. Using this approach drill will
> handle hive views the same way as if it was initially defined in Drill and
> persisted in .view.drill file.
> 5. For conversion of Hive types: from _*FieldSchema*_ to _*RelDataType*_
> we'll reuse existing code from _*DrillHiveTable*_, so the conversion
> functionality will be extracted and used for both (table and view) fields
> type conversions.
> *Security implications*
> Consider simple example case where we have users,
> {code:java}
> user0 user1 user2
> \ /
> group12
> {code}
> and sample db where object names contains user or group who should access
> them
> {code:java}
> db_all
> tbl_user0
> vw_user0
> tbl_group12
> vw_group12
> {code}
> There are two Hive authorization modes supported by Drill - SQL Standart and
> Strorage Based authorization. For SQL Standart authorization permissions
> were granted using SQL:
> {code:java}
> SET ROLE admin;
> GRANT SELECT ON db_all.tbl_user0 TO USER user0;
> GRANT SELECT ON db_all.vw_user0 TO USER user0;
> CREATE ROLE group12;
> GRANT ROLE group12 TO USER user1;
> GRANT ROLE group12 TO USER user2;
> GRANT SELECT ON db_all.tbl_group12 TO ROLE group12;
> GRANT SELECT ON db_all.vw_group12 TO ROLE group12;
> {code}
> And for Storage based authorization permissions were granted using commands:
> {code:java}
> hadoop fs -chown user0:user0 /user/hive/warehouse/db_all.db/tbl_user0
> hadoop fs -chmod 700 /user/hive/warehouse/db_all.db/tbl_user0
> hadoop fs -chmod 750 /user/hive/warehouse/db_all.db/tbl_group12
> hadoop fs -chown user1:group12
> /user/hive/warehouse/db_all.db/tbl_group12{code}
> Then the following table shows us results of queries for both authorization
> models.
>
> *SQL Standart | Storage Based
> Authorization*
> ||SQL||user0||user1||user2|| ||user0||user1||user2||
> |*Queries executed using Drill :*| | | | | | | |
> |SHOW TABLES IN hive.db_all;| all| all| all| |Accessibe tables + all
> views|Accessibe tables + all views|Accessibe tables + all views|
> |SELECT * FROM hive.db_all.tbl_user0;| (/)| (x)| (x)| | (/)|
> (x)| (x)|
> |SELECT * FROM hive.db_all.vw_user0;| (/)| (x)| (x)| | (/)|
> (x)| (x)|
> |SELECT * FROM hive.db_all.tbl_group12;| (x)| (/)| (/)| | (x)|
> (/)| (/)|
> |SELECT * FROM hive.db_all.vw_group12;| (x)| (/)| (/)| | (x)|
> (/)| (/)|
> |SELECT * FROM INFORMATION_SCHEMA.`TABLES`
> WHERE TABLE_SCHEMA = 'hive.db_all';| all| all| all| |Accessibe tables +
> all views|Accessibe tables + all views|Accessibe tables + all views|
> |DESCRIBE hive.db_all.tbl_user0;| (/)| (x)| (x)| | (/)|
> (x)| (x)|
> |DESCRIBE hive.db_all.vw_user0;| (/)| (x) | (x)| | (/)|
> (/)| (/)|
> |DESCRIBE hive.db_all.tbl_group12;| (x)| (/)| (/)| | (x)|
> (/) | (/)|
> |DESCRIBE hive.db_all.vw_group12;| (x)| (/)| (/)| | (/)|
> (/)| (/)|
> |*Queries executed using Beeline and Hive CLI:*| | | | | | | |
> |SHOW TABLES IN db_all;| all| all| all| | all| all|
> all|
> |SELECT * FROM hive.db_all.tbl_user0;| (/)| (x) | (x)| | (/)|
> (x)| (x)|
> |SELECT * FROM db_all.vw_user0;| (/)| (x)| (x)| | (/)|
> (x)| (x)|
> |SELECT * FROM db_all.tbl_group12;| (x)| (/)| (/)| | (x)|
> (/)| (/)|
> |SELECT * FROM db_all.vw_group12;| (x)| (/)| (/)| | (x)|
> (/)| (/)|
> | | | | | | | | |
> |DESCRIBE db_all.tbl_user0;| (/)| (x) | (x)| | (/)| (x)|
> (x)|
> |DESCRIBE db_all.vw_user0;| (/)| (x)| (x)| | (/)| (/)|
> (/)|
> |DESCRIBE db_all.tbl_group12;| (x)| (/)| (/)| | (x)|
> (/)| (/)|
> |DESCRIBE db_all.vw_group12;| (x) | (/)| (/)| | (/)|
> (/)| (/)|
> (!) *Warning:* Because views in Hive aren't present as physical files and
> access can't be granted using file system commands, then access to Hive views
> for *Storage Based Authorization* is based on the underlying tables used in
> view definition. For current example views were defined as selection over
> appropriate tables.
> *For documentation*
> Remove note from
> [https://drill.apache.org/docs/querying-the-information-schema/] that states:
> {noformat}
> NOTE
> Currently, Drill only supports querying Drill views; Hive views are not yet
> supported.
> {noformat}
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