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https://issues.apache.org/jira/browse/FLINK-5653?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15893813#comment-15893813
]
ASF GitHub Bot commented on FLINK-5653:
---------------------------------------
Github user shaoxuan-wang commented on a diff in the pull request:
https://github.com/apache/flink/pull/3443#discussion_r104096189
--- Diff:
flink-libraries/flink-table/src/main/java/org/apache/flink/table/plan/nodes/datastream/aggs/DoubleSummaryAggregation.java
---
@@ -0,0 +1,214 @@
+/*
+ * 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.plan.nodes.datastream.aggs;
+
+import static
org.apache.flink.api.java.summarize.aggregation.CompensatedSum.ZERO;
+
+import org.apache.flink.api.java.summarize.aggregation.Aggregator;
+import org.apache.flink.api.java.summarize.aggregation.CompensatedSum;
+import
org.apache.flink.api.java.summarize.aggregation.NumericSummaryAggregator;
+
+public class DoubleSummaryAggregation extends
NumericSummaryAggregator<Double> {
--- End diff --
@huawei-flink , I have replied your question in the UDAGG design doc.
AggregateFunction is the base class for UDAGG. We are very cautious to add any
new method into this interface. As mentioned in the UDAGG design doc, only
createAccumulator, getValue, accumulate are the must to have methods for an
aggregate. Merge methods is optional only useful for advanced optimization for
the runtime execution plan. Retract may also be a must-have if the users are
care about the correctness. I do not see why reset is necessary for aggregate.
If it is helpful in your case, you can always add this method in your User(you
as the user) Defined Aggregate Function. UDAGG is still on the way, but I think
it should be available very soon.
> Add processing time OVER ROWS BETWEEN x PRECEDING aggregation to SQL
> --------------------------------------------------------------------
>
> Key: FLINK-5653
> URL: https://issues.apache.org/jira/browse/FLINK-5653
> Project: Flink
> Issue Type: Sub-task
> Components: Table API & SQL
> Reporter: Fabian Hueske
> Assignee: Stefano Bortoli
>
> The goal of this issue is to add support for OVER ROWS aggregations on
> processing time streams to the SQL interface.
> Queries similar to the following should be supported:
> {code}
> SELECT
> a,
> SUM(b) OVER (PARTITION BY c ORDER BY procTime() ROWS BETWEEN 2 PRECEDING
> AND CURRENT ROW) AS sumB,
> MIN(b) OVER (PARTITION BY c ORDER BY procTime() ROWS BETWEEN 2 PRECEDING
> AND CURRENT ROW) AS minB
> FROM myStream
> {code}
> The following restrictions should initially apply:
> - All OVER clauses in the same SELECT clause must be exactly the same.
> - The PARTITION BY clause is optional (no partitioning results in single
> threaded execution).
> - The ORDER BY clause may only have procTime() as parameter. procTime() is a
> parameterless scalar function that just indicates processing time mode.
> - UNBOUNDED PRECEDING is not supported (see FLINK-5656)
> - FOLLOWING is not supported.
> The restrictions will be resolved in follow up issues. If we find that some
> of the restrictions are trivial to address, we can add the functionality in
> this issue as well.
> This issue includes:
> - Design of the DataStream operator to compute OVER ROW aggregates
> - Translation from Calcite's RelNode representation (LogicalProject with
> RexOver expression).
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