[jira] [Created] (CALCITE-7479) Remove redundant aggregate group keys with FD

["Zhen Chen (Jira)" <ji...@apache.org>]

Zhen Chen created CALCITE-7479:
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             Summary: Remove redundant aggregate group keys with FD
                 Key: CALCITE-7479
                 URL: https://issues.apache.org/jira/browse/CALCITE-7479
             Project: Calcite
          Issue Type: New Feature
          Components: core
    Affects Versions: 1.41.0
            Reporter: Zhen Chen


{*}Proposal{*}​
Add a new aggregate rewrite rule to identify and remove redundant grouping keys from an {{{}Aggregate{}}}that are functionally determined by preceding grouping keys. To preserve the original semantics, the rewrite will: * Shorten the grouping key list of the {{Aggregate}}
 * Use {{{}SINGLE_VALUE{}}}to restore the removed grouping column(s)
 * Reorder the output columns to match the original order using a {{Project}}

{*}Example of the Planned Change{*}​
Original SQL:
{code:java}
select deptno, name, count() as c
from sales.dept
group by deptno, name {code}
Original plan:
{code:java}
LogicalAggregate(group=[{0, 1}], C=[COUNT()])
  LogicalTableScan(table=[[CATALOG, SALES, DEPT]]) {code}
Rewritten plan:
{code:java}
LogicalProject(DEPTNO=[$0], NAME=[$1], C=[$2])
  LogicalAggregate(group=[{0}], NAME=[SINGLE_VALUE($1)], C=[COUNT()])
    LogicalTableScan(table=[[CATALOG, SALES, DEPT]]) {code}
{*}Explanation{*}​ * 
If {{{}name{}}}is functionally determined by {{{}deptno{}}}, then {{{}name{}}}is removed from the grouping keys.
 * 
{{{}SINGLE_VALUE{}}}is used to retain the value of the removed column semantically.
 * 
The {{{}Project{}}}restores the final output column order and field names.



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