[jira] [Assigned] (CALCITE-3876) MergeProjectRule should not combine Projects when top Project contains window function referencing window function from bottom Project

["Julian Hyde (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-3876?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Julian Hyde reassigned CALCITE-3876:
------------------------------------

    Assignee: Julian Hyde

> MergeProjectRule should not combine Projects when top Project contains window function referencing window function from bottom Project
> --------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: CALCITE-3876
>                 URL: https://issues.apache.org/jira/browse/CALCITE-3876
>             Project: Calcite
>          Issue Type: Bug
>            Reporter: Steven Talbot
>            Assignee: Julian Hyde
>            Priority: Major
>
> Here's a test in RelToSqlConverterTest that should (roughly) pass
> {code:java}
> @Test public void testWindowOnWindowDoesNotCombineProjects() {
>  final String query = "SELECT \n" +
>  " ROW_NUMBER() OVER (ORDER BY rn) FROM\n" +
>  " (SELECT *, \n" +
>  " ROW_NUMBER() OVER (ORDER BY \"product_id\") as rn\n" +
>  " FROM \"foodmart\".\"product\")";
>  final String expected = "SELECT \n" +
>  " ROW_NUMBER() OVER (ORDER BY rn) FROM\n" +
>  " (SELECT *, \n" +
>  " ROW_NUMBER() OVER (ORDER BY \"product_id\") as rn\n" +
>  " FROM \"foodmart\".\"product\")";
>  sql(query)
>  .withPostgresql()
>  .ok(expected);
> }{code}
> Instead, we see the result
> {noformat}
> SELECT ROW_NUMBER() OVER (ORDER BY ROW_NUMBER() OVER (ORDER BY \"product_id\"))\nFROM \"foodmart\".\"product\"{noformat}
> That's because multiple steps in the pipeline want to squish those two projects together, but that's not valid to do (at least in Redshift where I tested, but I assume in most other SQL dialects as well). 
> So the expected behavior is that SqlToRelConverter, RelBuilder, and RelToSqlConverter are all knowledgeable enough about window functions to examine the arguments and avoid merging projects (or combining SelectNode[s], in the case of RelToSqlConverter), when one window references another window.



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