[jira] [Commented] (HIVE-17041) Aggregate elimination with UNIQUE and NOT NULL column

["Vineet Garg (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-17041?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16616956#comment-16616956 ] 

Vineet Garg commented on HIVE-17041:
------------------------------------

Calcite uses RelOptTable's isKey api to determine the uniqueness. The implementation for this in RelOptHiveTable doesn't take into account the nullability of UNIQUE constraint, as a result calcite can end up removing UNIQUE constraint without NOT NULL column.
We should probably update isKey or generateKeys to take into account only PRIMARY KEYS and UNIQUE + NOT NULL columns. [~jcamachorodriguez] suggestions?

> Aggregate elimination with UNIQUE and NOT NULL column
> -----------------------------------------------------
>
>                 Key: HIVE-17041
>                 URL: https://issues.apache.org/jira/browse/HIVE-17041
>             Project: Hive
>          Issue Type: Sub-task
>          Components: Logical Optimizer
>    Affects Versions: 3.0.0
>            Reporter: Jesus Camacho Rodriguez
>            Assignee: Vineet Garg
>            Priority: Major
>         Attachments: HIVE-17041.1.patch
>
>
> If columns are part of a GROUP BY expression and they are UNIQUE and do not accept NULL values, i.e. PK or UK+NOTNULL, the _Aggregate_ operator can be transformed into a Project operator, as each row will end up in a different group.
> For instance, given that _pk_ is the PRIMARY KEY for the table, the GROUP BY could be removed from grouping columns for following query:
> {code:sql}
> SELECT pk, value1
> FROM table_1
> GROUP BY value1, pk, value2;
> {code}



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