Haisheng Yuan created CALCITE-4015:
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Summary: Pass through parent collation request on subset or
superset of join keys for EnumerableMergeJoin
Key: CALCITE-4015
URL: https://issues.apache.org/jira/browse/CALCITE-4015
Project: Calcite
Issue Type: Improvement
Components: core
Reporter: Haisheng Yuan
Pass through parent collation request on subset or superset of join keys for
EnumerableMergeJoin.
e.g.
{code:java}
select * from foo join bar on foo.a=bar.a and foo.b=bar.b order by b;
{code}
collation on b is passed to mergejoin, mergejoin should generate an alternative
with collation on b, a.
{code:java}
select * from foo join bar on foo.a=bar.a and foo.b=bar.b order by foo.a,
foo.b, foo.c;
{code}
collation on a,b,c is passed to mergejoin, mergejoin should generate an
alternative with collation on a,b,c, even the join keys are a,b, but since
foo.c is also the output column, mergejoin can still request its child foo to
deliver collation on a,b,c. The join keys must be the collation request's
prefixes.
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