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https://issues.apache.org/jira/browse/PHOENIX-2405?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15363659#comment-15363659
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ASF GitHub Bot commented on PHOENIX-2405:
-----------------------------------------
Github user maryannxue commented on a diff in the pull request:
https://github.com/apache/phoenix/pull/175#discussion_r69668528
--- Diff:
phoenix-core/src/main/java/org/apache/phoenix/execute/AggregatePlan.java ---
@@ -133,7 +134,10 @@ public PeekingResultIterator
newIterator(StatementContext context, ResultIterato
Expression expression = RowKeyExpression.INSTANCE;
OrderByExpression orderByExpression = new
OrderByExpression(expression, false, true);
int threshold =
services.getProps().getInt(QueryServices.SPOOL_THRESHOLD_BYTES_ATTRIB,
QueryServicesOptions.DEFAULT_SPOOL_THRESHOLD_BYTES);
- return new OrderedResultIterator(scanner,
Collections.<OrderByExpression>singletonList(orderByExpression), threshold);
+ String spoolDirectory =
services.getProps().get(QueryServices.SPOOL_DIRECTORY,
QueryServicesOptions.DEFAULT_SPOOL_DIRECTORY);
--- End diff --
In my previous review I might not have made it very clear that the idea of
moving MemoryManager into constructors was more of a question rather than
advice. Since I hadn't studied the code so carefully, I was trying to ask you
if that would be better, or worse? Looks like these parameters are getting all
over the place and my suggestion was not a good one?
> 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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