Lazily compile accumulators

Makes the tests about 5% faster on my laptop

presto-main/src/main/java/com/facebook/presto/operator/aggregation/AccumulatorFactoryBinder.java

@@ -0,0 +1,22 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.facebook.presto.operator.aggregation;
+
+import java.util.List;
+import java.util.Optional;
+
+public interface AccumulatorFactoryBinder
+{
+    AccumulatorFactory bind(List<Integer> argumentChannels, Optional<Integer> maskChannel, Optional<Integer> sampleWeightChannel, double confidence);
+}

presto-main/src/main/java/com/facebook/presto/operator/aggregation/AggregationCompiler.java

@@ -139,7 +139,7 @@ public List<InternalAggregationFunction> generateAggregationFunctions(Class<?> c
                             throw Throwables.propagate(e);
                         }
 
-                        GenericAccumulatorFactoryBinder factory = new AccumulatorCompiler().generateAccumulatorFactoryBinder(metadata, classLoader);
+                        AccumulatorFactoryBinder factory = new LazyAccumulatorFactoryBinder(metadata, classLoader);
                         builder.add(new InternalAggregationFunction(name, inputTypes, intermediateType, outputType, aggregationAnnotation.decomposable(), aggregationAnnotation.approximate(), factory));
                     }
                 }

presto-main/src/main/java/com/facebook/presto/operator/aggregation/GenericAccumulatorFactoryBinder.java

@@ -25,6 +25,7 @@
 import static com.google.common.base.Preconditions.checkNotNull;
 
 public class GenericAccumulatorFactoryBinder
+        implements AccumulatorFactoryBinder
 {
     private final boolean approximationSupported;
     private final AccumulatorStateSerializer<?> stateSerializer;
@@ -65,6 +66,7 @@ public GenericAccumulatorFactoryBinder(
         }
     }
 
+    @Override
     public AccumulatorFactory bind(List<Integer> argumentChannels, Optional<Integer> maskChannel, Optional<Integer> sampleWeightChannel, double confidence)
     {
         if (!approximationSupported) {

presto-main/src/main/java/com/facebook/presto/operator/aggregation/InternalAggregationFunction.java

@@ -30,9 +30,9 @@ public final class InternalAggregationFunction
     private final Type finalType;
     private final boolean decomposable;
     private final boolean approximate;
-    private final GenericAccumulatorFactoryBinder factory;
+    private final AccumulatorFactoryBinder factory;
 
-    public InternalAggregationFunction(String name, List<Type> parameterTypes, Type intermediateType, Type finalType, boolean decomposable, boolean approximate, GenericAccumulatorFactoryBinder factory)
+    public InternalAggregationFunction(String name, List<Type> parameterTypes, Type intermediateType, Type finalType, boolean decomposable, boolean approximate, AccumulatorFactoryBinder factory)
     {
         this.name = checkNotNull(name, "name is null");
         checkArgument(!name.isEmpty(), "name is empty");

presto-main/src/main/java/com/facebook/presto/operator/aggregation/LazyAccumulatorFactoryBinder.java

@@ -0,0 +1,38 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.facebook.presto.operator.aggregation;
+
+import com.facebook.presto.byteCode.DynamicClassLoader;
+import com.google.common.base.Supplier;
+import com.google.common.base.Suppliers;
+
+import java.util.List;
+import java.util.Optional;
+
+public class LazyAccumulatorFactoryBinder
+        implements AccumulatorFactoryBinder
+{
+    private final Supplier<AccumulatorFactoryBinder> binder;
+
+    public LazyAccumulatorFactoryBinder(AggregationMetadata metadata, DynamicClassLoader classLoader)
+    {
+        binder = Suppliers.memoize(() -> new AccumulatorCompiler().generateAccumulatorFactoryBinder(metadata, classLoader));
+    }
+
+    @Override
+    public AccumulatorFactory bind(List<Integer> argumentChannels, Optional<Integer> maskChannel, Optional<Integer> sampleWeightChannel, double confidence)
+    {
+        return binder.get().bind(argumentChannels, maskChannel, sampleWeightChannel, confidence);
+    }
+}