Github user kaspersorensen commented on a diff in the pull request:
https://github.com/apache/metamodel/pull/34#discussion_r36589971
--- Diff:
core/src/main/java/org/apache/metamodel/query/DefaultAggregateFunction.java ---
@@ -0,0 +1,63 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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 org.apache.metamodel.query;
+
+import org.apache.metamodel.schema.ColumnType;
+import org.apache.metamodel.util.AggregateBuilder;
+
+/**
+ * Implementation of the {@link
org.apache.metamodel.query.AggregateFunction}.
+ */
+public abstract class DefaultAggregateFunction<T> implements
AggregateFunction {
+
+ public abstract AggregateBuilder<T> createAggregateBuilder();
+
+ public abstract ColumnType getExpectedColumnType(ColumnType type);
+
+ public Object evaluate(Iterable<?> values) {
+ AggregateBuilder<?> builder = createAggregateBuilder();
+ for (Object object : values) {
+ builder.add(object);
+ }
+ return builder.getAggregate();
+ }
+
+ /**
+ * Executes the function
+ *
+ * @param values
+ * the values to be evaluated. If a value is null it won't
be
+ * evaluated
+ * @return the result of the function execution. The return type class
is
+ * dependent on the FunctionType and the values provided. COUNT
+ * yields a Long, AVG and SUM yields Double values and MAX and
MIN
+ * yields the type of the provided values.
+ */
+ public Object evaluate(Object... values) {
+ AggregateBuilder<?> builder = createAggregateBuilder();
+ for (Object object : values) {
+ builder.add(object);
+ }
+ return builder.getAggregate();
+ }
+
+ @Override
+ public String toString() { return getFunctionName(); }
--- End diff --
and here too :)
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