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https://issues.apache.org/jira/browse/PHOENIX-2405?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15364909#comment-15364909
]
ASF GitHub Bot commented on PHOENIX-2405:
-----------------------------------------
Github user RCheungIT commented on a diff in the pull request:
https://github.com/apache/phoenix/pull/175#discussion_r69792221
--- Diff:
phoenix-core/src/main/java/org/apache/phoenix/iterate/SpoolingByteBufferSegmentQueue.java
---
@@ -0,0 +1,357 @@
+/*
+ * 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.phoenix.iterate;
+
+import org.apache.commons.io.input.CountingInputStream;
+import org.apache.commons.io.output.DeferredFileOutputStream;
+
+import org.apache.phoenix.memory.MemoryManager;
+import org.apache.phoenix.memory.MemoryManager.MemoryChunk;
+import org.apache.phoenix.query.QueryServices;
+import org.apache.phoenix.query.QueryServicesOptions;
+
+
+import java.io.*;
+import java.util.AbstractQueue;
+import java.util.Iterator;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.apache.phoenix.monitoring.GlobalClientMetrics.*;
+
+
+public abstract class SpoolingByteBufferSegmentQueue<T> extends
AbstractQueue<T> {
--- End diff --
Hi @maryannxue, it seems that I get your idea now. Do you mean I should not
change the sort logic in memory? What I only need to do is modify the flush
logic, flush the sorted result to SpoolingResultIterator. Is that correct?
Thanks.
> Improve performance and stability of server side sort for ORDER BY
> ------------------------------------------------------------------
>
> Key: PHOENIX-2405
> URL: https://issues.apache.org/jira/browse/PHOENIX-2405
> Project: Phoenix
> Issue Type: Bug
> Reporter: James Taylor
> Assignee: Haoran Zhang
> Labels: gsoc2016
> Fix For: 4.8.0
>
>
> We currently use memory mapped files to buffer data as it's being sorted in
> an ORDER BY (see MappedByteBufferQueue). The following types of exceptions
> have been seen to occur:
> {code}
> Caused by: java.lang.OutOfMemoryError: Map failed
> at sun.nio.ch.FileChannelImpl.map0(Native Method)
> at sun.nio.ch.FileChannelImpl.map(FileChannelImpl.java:904)
> {code}
> [~apurtell] has read that memory mapped files are not cleaned up after very
> well in Java:
> {quote}
> "Map failed" means the JVM ran out of virtual address space. If you search
> around stack overflow for suggestions on what to do when your app (in this
> case Phoenix) encounters this issue when using mapped buffers, the answers
> tend toward manually cleaning up the mapped buffers or explicitly triggering
> a full GC. See
> http://stackoverflow.com/questions/8553158/prevent-outofmemory-when-using-java-nio-mappedbytebuffer
> for example. There are apparently long standing JVM/JRE problems with
> reclamation of mapped buffers. I think we may want to explore in Phoenix a
> different way to achieve what the current code is doing.
> {quote}
> Instead of using memory mapped files, we could use heap memory, or perhaps
> there are other mechanisms too.
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