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https://issues.apache.org/jira/browse/CALCITE-6652?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17903855#comment-17903855
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suibianwanwan edited comment on CALCITE-6652 at 2/5/25 12:36 PM:
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Hi, [~julianhyde]. As discussed in CALCITE-1317, we can't do a conversion
between max and order by limit 1 when rowCount is empty.
Edit:
in the decorrelate, we add correlated variables to the group list to ensure
equivalence when Correlate is transformed to Join. When the group list is
non-empty, MIN/MAX will also return 0 rows if input with 0 rows.(This behavior
also leads to the issue described in [CALCITE-5743]). So if corVar exists, the
conversion is valid.
was (Author: JIRAUSER301334):
Hi, [~julianhyde]. As discussed in CALCITE-1317, we can't do a conversion
between max and order by limit 1 when rowCount is empty.
Edit: Sorry for doing too much editing, the logic here should be that the
conversion is valid if a particular RelNode, for a row of 0 outputs the same
result as a null row. One scenario is in a Filter where the condition satisfies
Strong.isNotTrue()
> RelDecorrelator can't decorrelate query with limit 1
> ----------------------------------------------------
>
> Key: CALCITE-6652
> URL: https://issues.apache.org/jira/browse/CALCITE-6652
> Project: Calcite
> Issue Type: Bug
> Reporter: suibianwanwan
> Assignee: suibianwanwan
> Priority: Major
>
> The following query can't decorrelate by RelDecorrelate:
> {code:java}
> @Test void testDecorrelateFetchOne1() {
> final String query = "SELECT deptno FROM dept WHERE\n" +
> "1000 > (SELECT sal FROM emp WHERE dept.deptno = emp.deptno order by
> emp.sal limit 1)";
> sql(query).withRule(
> CoreRules.FILTER_SUB_QUERY_TO_CORRELATE)
> .withLateDecorrelate(true)
> .check();
> }{code}
> is equivalent to the following query, and the following query can be
> decorrelated into a join, so we can do some appropriate conversions in
> RelDecorrelate:
> {code:java}
> @Test void testDecorrelateFetchOne1() {
> final String query = "SELECT deptno FROM dept WHERE\n" +
> "1000 > (SELECT min(sal) FROM emp WHERE dept.deptno = emp.deptno)";
> sql(query).withRule(
> CoreRules.FILTER_SUB_QUERY_TO_CORRELATE)
> .withLateDecorrelate(true)
> .check();
> }{code}
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