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https://issues.apache.org/jira/browse/CALCITE-3876?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17067922#comment-17067922
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Julian Hyde edited comment on CALCITE-3876 at 3/26/20, 6:14 PM:
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Let's mark this as related CALCITE-3079. But this case may not even invoke
{{ProjectToWindowRule}}. There is likely a bigger a problem in
{{ProjectMergeRule}}.
If so, change the summary to name the villain: ProjectMergeRule.
was (Author: julianhyde):
Let's mark this as related CALCITE-3079. But this case may not even invoke
{{ProjectToWindowRule}}. There is likely a bigger a problem in
{{ProjectMergeRule}}.
> 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
> 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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