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https://issues.apache.org/jira/browse/CALCITE-6413?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17862822#comment-17862822
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Julian Hyde commented on CALCITE-6413:
--------------------------------------
We do convert NATURAL and USING to ON - in fact we have to, because our
relational algebra (class Join) only supports the latter. But we don’t do that
rewrite until validation is complete. Mutating the AST during validation is a
bad idea.
> SqlValidator does not invoke TypeCoercionImpl::binaryComparisonCoercion for
> both NATURAL and USING join conditions
> -------------------------------------------------------------------------------------------------------------------
>
> Key: CALCITE-6413
> URL: https://issues.apache.org/jira/browse/CALCITE-6413
> Project: Calcite
> Issue Type: Improvement
> Reporter: Maksim Zhuravkov
> Assignee: Pavel Pereslegin
> Priority: Minor
>
> This can be observed by adding these test cases to `SqlToRelConverterTest`:
> 1. Join condition ON expression
> {code:java}
> @Test void test1() {
> final String sql = "select * from emp JOIN (VALUES ('XXX')) t(deptno) ON
> emp.deptno = t.deptno";
> sql(sql).ok();
> }
> {code}
> 2. Common columns (USING/NATURAL) (since they both share the same code path
> for building join condition)
> {code:java}
> @Test void test2() {
> final String sql = "select * from emp JOIN (VALUES ('XXX')) t(deptno)
> USING (deptno)";
> sql(sql).ok();
> }
> {code}
> When test 1 runs, the SqlValidator calls
> TypeCoercionImpl::binaryComparisonCoercion
> When test 2 runs, the SqlValidator does not call
> TypeCoercionImpl::binaryComparisonCoercion.
>
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