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https://issues.apache.org/jira/browse/FLINK-6969?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16062986#comment-16062986
]
ASF GitHub Bot commented on FLINK-6969:
---------------------------------------
Github user wuchong commented on a diff in the pull request:
https://github.com/apache/flink/pull/4183#discussion_r123989779
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/runtime/triggers/DeferredComputationTrigger.scala
---
@@ -0,0 +1,83 @@
+/*
+ * 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.runtime.triggers
+
+import org.apache.flink.streaming.api.windowing.triggers.{Trigger,
TriggerResult}
+import
org.apache.flink.streaming.api.windowing.triggers.Trigger.{OnMergeContext,
TriggerContext}
+import org.apache.flink.streaming.api.windowing.windows.TimeWindow
+import org.apache.flink.table.api.StreamQueryConfig
+
+/**
+ * A [[Trigger]] that onElement method never fires the window, and only
fires when current
+ * watermark not smaller than (window.maxTimestamp +
queryConfig.getDeferredComputationTime)
+ */
+class DeferredComputationTrigger(queryConfig: StreamQueryConfig) extends
Trigger[Any, TimeWindow] {
--- End diff --
I think the parameter can be only a `deferredComputationTime : Long`. It
shouldn't be associated to StreamQueryConfig.
> Add support for deferred computation for group window aggregates
> ----------------------------------------------------------------
>
> Key: FLINK-6969
> URL: https://issues.apache.org/jira/browse/FLINK-6969
> Project: Flink
> Issue Type: New Feature
> Components: Table API & SQL
> Reporter: Fabian Hueske
> Assignee: sunjincheng
>
> Deferred computation is a strategy to deal with late arriving data and avoid
> updates of previous results. Instead of computing a result as soon as it is
> possible (i.e., when a corresponding watermark was received), deferred
> computation adds a configurable amount of slack time in which late data is
> accepted before the result is compute. For example, instead of computing a
> tumbling window of 1 hour at each full hour, we can add a deferred
> computation interval of 15 minute to compute the result quarter past each
> full hour.
> This approach adds latency but can reduce the number of update esp. in use
> cases where the user cannot influence the generation of watermarks. It is
> also useful if the data is emitted to a system that cannot update result
> (files or Kafka). The deferred computation interval should be configured via
> the {{QueryConfig}}.
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