Vladimir Sitnikov created CALCITE-452:
-----------------------------------------
Summary: JavaRowFormat.comparer relies on proper equals/compareTo
in custom row classes
Key: CALCITE-452
URL: https://issues.apache.org/jira/browse/CALCITE-452
Project: Calcite
Issue Type: Bug
Affects Versions: 0.9.1
Reporter: Vladimir Sitnikov
Assignee: Julian Hyde
Priority: Minor
When reviewing CALCITE-397 I noted that the fix was "convert to the target row
type, then perform distinct".
I wondered: why don't we perform distinct first, then convert row types? That
might be much more efficient if the distinct reduces the number of rows
dramatically, so we do not spend time on conversion.
When I did tried this change, I noticed Calcite uses "default equals/compareTo".
Not sure what is the best approach here: raise errors in such cases, create
synthetic equals/hashCode/compareTo somehow, or reconvert to the type with
proper comparison methods.
Here's the change to use "distinct, then convert to the target physType":
{code:java}
Expressions.return_(
null,
+ inputPhysType.convertTo(
Expressions.call(
+ childExp,
- inputPhysType.convertTo(childExp, physType),
BuiltinMethod.DISTINCT.method,
Expressions.<Expression>list()
.appendIfNotNull(inputPhysType.comparer()))
+ , physType)
));
{code}
The generated java code is as following (note how {{.distinct()}} is used over
{{JdbcTest$Employee}} that has no {{equals/compareTo}} methods):
{code:java}
/* 3 */ public net.hydromatic.linq4j.Enumerable bind(final
net.hydromatic.optiq.DataContext root0) {
/* 4 */ root = root0;
/* 5 */ return
net.hydromatic.linq4j.Linq4j.asEnumerable(((net.hydromatic.optiq.test.JdbcTest.HrSchema)
((net.hydromatic.optiq.impl.java.ReflectiveSchema)
root.getRootSchema().getSubSchema("hr").unwrap(net.hydromatic.optiq.impl.java.ReflectiveSchema.class)).getTarget()).emps).distinct().select(new
net.hydromatic.linq4j.function.Function1() {
/* 6 */ public Object[]
apply(net.hydromatic.optiq.test.JdbcTest.Employee o) {
/* 7 */ return new Object[] {
/* 8 */ o.empid,
/* 9 */ o.deptno,
/* 10 */ o.name,
/* 11 */ o.salary,
/* 12 */ o.commission};
/* 13 */ }
/* 14 */ public Object apply(Object o) {
/* 15 */ return apply(
/* 16 */ (net.hydromatic.optiq.test.JdbcTest.Employee) o);
/* 17 */ }
/* 18 */ }
/* 19 */ );
/* 20 */ }
{code}
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