Luis Fernando Kauer created CALCITE-1876:
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Summary: Create a rule to push the projections used in aggregate
functions
Key: CALCITE-1876
URL: https://issues.apache.org/jira/browse/CALCITE-1876
Project: Calcite
Issue Type: Improvement
Components: csv-adapter
Reporter: Luis Fernando Kauer
Assignee: Julian Hyde
Priority: Minor
>From Julian Hyde;
"Calcite should realize that Aggregate has an implied Project (because it only
uses a few columns) and push that projection into the CsvTableScan, but it
doesn’t."
A query scans only the used projection when no aggregation is used:
sql->explain plan for select name from emps;
CsvTableScan(table=[[SALES, EMPS]], fields=[[1]])
But it scans all the projections when an aggregation is used:
sql->explain plan for select max(name) from emps;
EnumerableAggregate(group=[{}], EXPR$0=[MAX($1)])
CsvTableScan(table=[[SALES, EMPS]], fields=[[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]])
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