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https://issues.apache.org/jira/browse/CALCITE-1876?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Julian Hyde updated CALCITE-1876:
---------------------------------
Description:
Create a rule to push the projections used in aggregate functions. From Julian
Hyde:
bq. 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:
{code}
explain plan for select name from emps;
CsvTableScan(table=[[SALES, EMPS]], fields=[[1]])
{code}
But it scans all the projections when an aggregation is used:
{code}
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]])
{code}
was:
>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]])
> Push projections through Aggregate to CsvTableScan
> --------------------------------------------------
>
> 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
>
> Create a rule to push the projections used in aggregate functions. From
> Julian Hyde:
> bq. 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:
> {code}
> explain plan for select name from emps;
> CsvTableScan(table=[[SALES, EMPS]], fields=[[1]])
> {code}
> But it scans all the projections when an aggregation is used:
> {code}
> 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]])
> {code}
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