@Override
public PhysicalOperator visitCollapsingAggregate(CollapsingAggregate agg, Object value)
throws OptimizerException {
if (!(agg.getInput() instanceof Segment)) {
throw new OptimizerException(
String.format(
"Currently, Drill only supports CollapsingAggregate immediately preceded by a Segment. The input of this operator is %s.",
agg.getInput()));
}
Segment segment = (Segment) agg.getInput();
if (!agg.getWithin().equals(segment.getName())) {
throw new OptimizerException(
String.format(
"Currently, Drill only supports CollapsingAggregate immediately preceded by a Segment where the CollapsingAggregate works on the defined segments. In this case, the segment has been defined based on the name %s but the collapsing aggregate is working within the field %s.",
segment.getName(), agg.getWithin()));
}
// a collapsing aggregate is a currently implemented as a sort followed by a streaming
// aggregate.
List<OrderDef> orderDefs = Lists.newArrayList();
List<NamedExpression> keys = Lists.newArrayList();
for (LogicalExpression e : segment.getExprs()) {
if (!(e instanceof SchemaPath))
throw new OptimizerException(
"The basic optimizer doesn't currently support collapsing aggregate where the segment value is something other than a SchemaPath.");
keys.add(new NamedExpression(e, new FieldReference((SchemaPath) e)));
orderDefs.add(new OrderDef(Direction.ASC, e));
}
Sort sort = new Sort(segment.getInput().accept(this, value), orderDefs, false);
StreamingAggregate sa =
new StreamingAggregate(
sort, keys.toArray(new NamedExpression[keys.size()]), agg.getAggregations(), 1.0f);
return sa;
}