John Fang created CALCITE-2102:
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Summary: RelCollation should have a constraint to limit the repeat
or incompatible RelFieldCollations.
Key: CALCITE-2102
URL: https://issues.apache.org/jira/browse/CALCITE-2102
Project: Calcite
Issue Type: Bug
Reporter: John Fang
Assignee: Julian Hyde
I test the query "SELECT a, c FROM MyTable ORDER BY a DESC, a DESC". And
the collation of LogicalSort is "[0 DESC, 0 DESC]" , thus it will order by the
repeater fields. I think the calcite should removal the repeated fields, thus
it make the LogicalSort whose collation is "[0 DESC]" be more reasonable.
Considering compatibility，it may be better make SqlToRelConverter (or
perhaps RelBuilder) ignore sort keys that have appeared earlier in the key. In
addition, it should also prevent the incompatible sort keys. It should throw
illegalargumentexception for the query "SELECT a, c FROM MyTable ORDER BY a
DESC, a ASC" because of the incompatibility.
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