[jira] [Assigned] (ASTERIXDB-3462) Incorrect cardinality estimation with multicolumn PK-PK self joins

["Vijay Sarathy (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ASTERIXDB-3462?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Vijay Sarathy reassigned ASTERIXDB-3462:
----------------------------------------

    Assignee: Vijay Sarathy

> Incorrect cardinality estimation with multicolumn PK-PK self joins
> ------------------------------------------------------------------
>
>                 Key: ASTERIXDB-3462
>                 URL: https://issues.apache.org/jira/browse/ASTERIXDB-3462
>             Project: Apache AsterixDB
>          Issue Type: Bug
>          Components: COMP - Compiler
>            Reporter: Vijay Sarathy
>            Assignee: Vijay Sarathy
>            Priority: Major
>
> Consider the orders collection in CH2 which has (o_id, o_w_id, and o_d_id) as the composite PK. The following query,
> {code:java}
> select count(*) from orders x, orders y
>  where x.o_id = y.o_id AND y.o_w_id = x.o_w_id AND y.o_d_id = x.o_d_id
> {code}
> The overall cardinality of this should be the cardinality of orders since the join is a PK-PK join. However, we underestimate this cardinality as we do not recognize the composite PK.



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