Chunwei Lei created CALCITE-3015:
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Summary: Add rule to remove constants in group keys
Key: CALCITE-3015
URL: https://issues.apache.org/jira/browse/CALCITE-3015
Project: Calcite
Issue Type: Improvement
Reporter: Chunwei Lei
Assignee: Chunwei Lei
Constants in group keys can be removed to reduce shuffle. For instance,
{code:java}
select key, count(*) from (select 1 as key from src) dual group by key;
{code}
can be reduced to
{code:java}
select count(*) from (select 1 as key from src) dual;{code}
It could save much resource in distribute system if all group keys are
constants since the distribution becomes {{SINGLETON}} instead of {{HASH}}.
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