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.
I think we need a new rule for Aggregate on a TableScan of a
ProjectableFilterableTable. Can you create a JIRA case please?
I created a test case. It currently fails:
diff --git a/example/csv/src/test/java/org/apache/calcite/test/CsvTest.java
b/example/csv/src/test/java/org/apache/calcite/test/CsvTest.java
index 00c59ee..2402872 100644
--- a/example/csv/src/test/java/org/apache/calcite/test/CsvTest.java
+++ b/example/csv/src/test/java/org/apache/calcite/test/CsvTest.java
@@ -241,6 +241,13 @@ public Void apply(ResultSet resultSet) {
.ok();
}
+ @Test public void testAggregateImpliesProject() throws SQLException {
+ final String sql = "select max(name) from EMPS";
+ final String plan = "PLAN=EnumerableAggregate(group=[{}],
EXPR$0=[MAX($0)])\n"
+ + " CsvTableScan(table=[[SALES, EMPS]], fields=[[1]])\n";
+ sql("smart", "explain plan for " + sql).returns(plan).ok();
+ }
+
@Test public void testFilterableSelect() throws SQLException {
sql("filterable-model", "select name from EMPS").ok();
}
Julian
> On Jul 6, 2017, at 1:23 PM, Luis Fernando Kauer
> <[email protected]> wrote:
>
> Hi,
> I'm trying to understand the CSV Adapter and how the rules are fired.The
> CsvProjectTableScanRule gets fired when I use CsvTranslatableTable.But I'm
> not understanding why I'm getting a plan that scans all fields when I use an
> aggregate function.For example:explain plan for select name from
> emps;CsvTableScan(table=[[SALES, EMPS]], fields=[[1]])
>
> 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]])
> I noticed that the rule gets fired and at that point it shows just 1 field
> being used.But the last time CsvTableScan.deriveRowType() gets called it has
> all the fields set, and it's not the instance create by the rule, but the
> first instance created with all the fields.
> Can anybody explain me if this is a bug or if this is supposed to happen with
> aggregate functions ?
> Best regards,
> Luis Fernando Kauer
