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https://issues.apache.org/jira/browse/FLINK-10689?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16696605#comment-16696605
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ASF GitHub Bot commented on FLINK-10689:
----------------------------------------
twalthr commented on a change in pull request #7059: [FLINK-10689][table] Port
UDFs in Table API extension points to flink-table-common
URL: https://github.com/apache/flink/pull/7059#discussion_r235888670
##########
File path:
flink-libraries/flink-table-common/src/main/java/org/apache/flink/table/functions/AggregateFunction.java
##########
@@ -0,0 +1,143 @@
+/*
+ * 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.flink.table.functions;
+
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+
+/**
+ * Base class for User-Defined Aggregates.
+ *
+ * <p>The behavior of an {@link AggregateFunction} can be defined by
implementing a series of custom
+ * methods. An {@link AggregateFunction} needs at least three methods:
+ * - createAccumulator,
+ * - accumulate, and
+ * - getValue.
+ *
+ * <p>There are a few other methods that can be optional to have:
+ * - retract,
+ * - merge, and
+ * - resetAccumulator
+ *
+ * <p>All these methods must be declared publicly, not static and named
exactly as the names
+ * mentioned above. The methods createAccumulator and getValue are defined in
the
+ * {@link AggregateFunction} functions, while other methods are explained
below.
+ *
+ * <p>Processes the input values and update the provided accumulator instance.
The method
+ * accumulate can be overloaded with different custom types and arguments. An
AggregateFunction
+ * requires at least one accumulate() method.
+ *
+ * {@code
+ * param accumulator the accumulator which contains the current
aggregated results
+ * param userDefinedInputs the input value (usually obtained from a new
arrived data).
+ *
+ * def accumulate(accumulator: ACC, userDefinedInputs): Unit
Review comment:
Remove Scala code in all comments.
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> Port UDFs in Table API extension points to flink-table-common
> -------------------------------------------------------------
>
> Key: FLINK-10689
> URL: https://issues.apache.org/jira/browse/FLINK-10689
> Project: Flink
> Issue Type: Sub-task
> Components: Table API & SQL
> Reporter: Timo Walther
> Assignee: xueyu
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.8.0
>
>
> After FLINK-10687 and FLINK-10688 have been resolved, we should also port the
> remaining extension points of the Table API to flink-table-common. This
> includes interfaces for UDFs and the external catalog interface.
> This ticket is for porting UDFs. This jira does NOT depend on FLINK-16088 so
> it can be started at anytime.
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