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https://issues.apache.org/jira/browse/CALCITE-2081?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16373345#comment-16373345
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Julian Hyde commented on CALCITE-2081:
--------------------------------------
Reviewing
[PR|https://github.com/apache/calcite/pull/634/commits/71d8256573b2d57180306658aab8764636d36338].
You have the right algorithm, but you're using
{{EnumerableRelImplementor.map}} for a purpose it was not intended for. I think
you should add a {{int windowCount}} field to {{EnumerableRelImplementor}}.
Also, please move the test case from {{JdbcTest}} to {{winagg.iq}}.
> NPE in join of 2 subqueries using window functions
> --------------------------------------------------
>
> Key: CALCITE-2081
> URL: https://issues.apache.org/jira/browse/CALCITE-2081
> Project: Calcite
> Issue Type: Bug
> Reporter: Luis Fernando Kauer
> Assignee: Julian Hyde
> Priority: Major
>
> NPE when joining 2 subqueries that use window functions.
> Testing with a new test case in JdbcTest:
> {code}
> /** Tests for a join of subqueries using Window Functions */
> @Test public void testJoinWithWinAgg() {
> final String sql = "select a.*, b.r from\n"
> + "(select \"deptno\", first_value(\"empid\") over \n"
> + "(partition by \"deptno\" order by \"commission\") as r\n"
> + "from \"hr\".\"emps\") a\n"
> + "left join\n"
> + "(select \"deptno\", last_value(\"empid\") over \n"
> + "(partition by \"deptno\" order by \"commission\") as r\n"
> + "from \"hr\".\"emps\") b\n"
> + "on a.\"deptno\" = b.\"deptno\"";
> CalciteAssert.hr()
> .query(sql)
> .runs();
> }
> {code}
> Debugging this I found out that the NPE occurs at Expressions.declare (line
> 2937) in initializer.getType() because initializer is null. The statement is
> {code}
> int prevStart;
> {code}
> This statement does not have an initializer, but the method "declare" is
> trying to get the initializer's type, generating NPE.
> This happens when joining 2 subqueries that use window functions because they
> end up using the same variables. In BlockBuilder.append (line 124) it checks
> if the variable already exists and the problem starts there.
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