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https://issues.apache.org/jira/browse/CALCITE-2978?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16884979#comment-16884979
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Pressenna commented on CALCITE-2978:
------------------------------------
So I think I finally found a valid use case for this:
{code:java}
CREATE TABLE lookup (id INT, name TEXT, rank INT);
INSERT INTO lookup VALUES (1, 'GOOD', 1);
INSERT INTO lookup VALUES (2, 'GOOD', 3);
INSERT INTO lookup VALUES (2, 'GOOD', 2);
CREATE TABLE facts (id INT, name TEXT);
INSERT INTO facts VALUES (1, 'GOOD');
INSERT INTO facts VALUES (2, 'BAD');
SELECT id, (SELECT lookup.id FROM lookup WHERE lookup.name=facts.name) FROM
facts;
-- In this cases, the order must be preserved.
SELECT id, (SELECT lookup.id FROM lookup WHERE lookup.name=facts.name ORDER BY
lookup.rank ASC) FROM facts;
-- In this cases, the order must be preserved.
SELECT id, (SELECT lookup.id FROM lookup WHERE lookup.name=facts.name ORDER BY
lookup.rank DESC) FROM facts;
{code}
> sorting not applied in subqueries
> ---------------------------------
>
> Key: CALCITE-2978
> URL: https://issues.apache.org/jira/browse/CALCITE-2978
> Project: Calcite
> Issue Type: Bug
> Affects Versions: 1.19.0
> Reporter: Pressenna
> Assignee: Danny Chan
> Priority: Major
>
> {code:sql}
> CREATE TABLE test (id INT, val INT);
> INSERT INTO test VALUES (1,1);
> INSERT INTO test VALUES (2,2);
> INSERT INTO test VALUES (3,3);
> INSERT INTO test VALUES (4,4);
> SELECT id FROM (SELECT id, val FROM test ORDER BY val DESC);
> {code}
> Looks like CALCITE-2798 removes the sorting in sub-queries too aggressively.
> Update:
> I might be wrong here and jumped the gun too early.
> Looks like SQL does not dictate that the outer query has to retain any order
> of the inner query.
> The sort is applied if a {{LIMIT}} is specified in the inner query, to reduce
> the inner result correctly.
> Happy to close as invalid.
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