[jira] [Commented] (CALCITE-4486) UNIQUE predicate

["duan xiong (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-4486?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17417888#comment-17417888 ] 

duan xiong commented on CALCITE-4486:
-------------------------------------

[~julianhyde] Hi. This PR has been review for a month. I think it is a good shape. So If you have free time, Please do the final review. Thanks again.

> UNIQUE predicate
> ----------------
>
>                 Key: CALCITE-4486
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4486
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>            Reporter: Julian Hyde
>            Assignee: duan xiong
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.28.0
>
>          Time Spent: 0.5h
>  Remaining Estimate: 0h
>
> Implement the UNIQUE predicate, as specified by the SQL standard.
> Example:
> {code:java}
> UNIQUE (SELECT publishedIn FROM Book
>             WHERE authorId = 3)
> NOT UNIQUE (SELECT publishedIn FROM BOOK
>             WHERE authorId = 3)
> {code}
> {{UNIQUE}} returns {{FALSE}} if the query returns two or more rows that do not include NULL values and are equal. Like {{EXISTS}}, it never returns {{UNKNOWN}}.
> More details at [JOOQ|https://www.jooq.org/doc/3.0/manual/sql-building/conditional-expressions/unique-predicate/].
> This Issue support the UNIQUE predicate by set {{isExpand}} to return false, so sub-queries are converted to {{RexSubQuery}} expressions and handled later by {{SubQueryRemoveRule}}.



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