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https://issues.apache.org/jira/browse/DRILL-5517?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16069342#comment-16069342
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ASF GitHub Bot commented on DRILL-5517:
---------------------------------------
Github user paul-rogers commented on a diff in the pull request:
https://github.com/apache/drill/pull/840#discussion_r124950905
--- Diff:
exec/vector/src/main/java/org/apache/drill/exec/vector/VectorUtils.java ---
@@ -0,0 +1,56 @@
+/*
+ * 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.drill.exec.vector;
+
+public class VectorUtils {
+
+ /**
+ * Vectors cannot be any larger than the Netty memory allocation
+ * block size.
+ */
+
+ private static final int ABSOLUTE_MAX_SIZE = 16 * 1024 * 1024;
+ private static final int ABSOLUTE_MIN_SIZE = 16 * 1024;
--- End diff --
This code allows a boot-time option to limit maximum vector size. I thought
it would be handy for testing, but turned out not to be necessary, so I might
remove it.
To prevent failures when the value is set wrong, I clamped the value to
some minimum and maximum. The maximum is set by the Netty block size. The
minimum I just made up: seems if we limit vector size to much smaller than 16 K
we'd be unlikely to make progress.
Added a comment to clarify.
> Provide size-aware set operations in value vectors
> --------------------------------------------------
>
> Key: DRILL-5517
> URL: https://issues.apache.org/jira/browse/DRILL-5517
> Project: Apache Drill
> Issue Type: Improvement
> Affects Versions: 1.11.0
> Reporter: Paul Rogers
> Assignee: Paul Rogers
> Labels: ready-to-commit
> Fix For: 1.11.0
>
>
> DRILL-5211 describes a memory fragmentation issue in Drill. The resolution is
> to limit vector sizes to 16 MB (the size of Netty memory allocation "slabs.")
> Effort starts by providing "size-aware" set operations in value vectors which:
> * Operate as {{setSafe()}} while vectors are below 16 MB.
> * Throw a new, specific exception ({{VectorOverflowException}}) if setting
> the value (and growing the vector) would exceed the vector limit.
> The methods in value vectors then become the foundation on which we can
> construct size-aware record batch "writers."
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