[GitHub] [nifi] simonbence commented on a change in pull request #4839: NIFI-8113 Adding persistent status history repository backed by embedded QuestDB

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simonbence commented on a change in pull request #4839:
URL: https://github.com/apache/nifi/pull/4839#discussion_r581741855



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File path: nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/status/history/EmbeddedQuestDbRolloverHandler.java
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@@ -0,0 +1,121 @@
+/*
+ * 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.nifi.controller.status.history;
+
+import io.questdb.cairo.sql.Record;
+import io.questdb.cairo.sql.RecordCursor;
+import io.questdb.cairo.sql.RecordCursorFactory;
+import io.questdb.griffin.SqlCompiler;
+import io.questdb.griffin.SqlExecutionContext;
+import org.apache.commons.lang3.time.FastDateFormat;
+import org.apache.nifi.controller.status.history.questdb.QuestDbContext;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * QuestDB does not provide the possibility for deleting individual lines. Instead there is the option to drop older
+ * partitions. In order to clean up older status information, the partitions are outside of the scope of data we intend
+ * to keep will be deleted.
+ */
+public class EmbeddedQuestDbRolloverHandler implements Runnable {

Review comment:
       I wanted to go with a more general term. The key point of this feature is to prevent the data set from ever growing. One way is the purge the data, but in the long run I would like to extend this with some aggregating features: older data chunks will be merged to represent bigger amount of time.




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