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https://issues.apache.org/jira/browse/ARROW-1922?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16291373#comment-16291373
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ASF GitHub Bot commented on ARROW-1922:
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icexelloss commented on a change in pull request #1419: ARROW-1922: Blog post
on JAVA vector changes
URL: https://github.com/apache/arrow/pull/1419#discussion_r157032717
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File path: site/_posts/2017-12-13-java-vector-improvements.md
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@@ -0,0 +1,110 @@
+---
+layout: post
+title: "Improved JAVA Vector APIs"
+excerpt: "This post describes the recent improvements in JAVA Vector code"
+date: 2017-12-13 12:50:00
+author: Siddharth Teotia
+categories: [application]
+---
+
+<!--
+{% comment %}
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+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
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+http://www.apache.org/licenses/LICENSE-2.0
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+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.
+{% endcomment %}
+-->
+
+
+This post gives insight into the major improvements in the JAVA implementation
+of vectors.
+
+## Design Goals
+
+1. Improved Maintainability and Extensibility.
+2. Improved heap usage.
+3. No performance overhead on hot code paths.
+
+## Background
+
+**Improved Maintainability and Extensibility**
+
+We use templates in several places for compile time JAVA code generation for
+different vector classes, readers, writers etc. Templates are helpful as the
+developers don't have to write a lot of duplicate code.
+
+However, we realized that over a period of time some specific JAVA
+templates became extremely complex with giant if-else blocks, poor code
indentation
+and documentation. All this impacted the ability to easily extend these
templates
+for adding new functionality or improving the existing infrastructure.
+
+So we evaluated the usage of templates for compile time code generation and
+decided not to use complex templates in some places by writing small amount of
+duplicate code which is elegant, well documented and extensible.
+
+**Improved Heap Usage**
+
+We did extensive memory analysis downstream in Dremio where Arrow is used
+heavily for in-memory query execution on columnar data. The general conclusion
+was that Arrow JAVA Vectors have non-negligible heap overhead and volume of
+objects was too high. There were places in code where we were creating objects
+unnecessarily and using structures that could be substituted with better
+alternatives.
+
+**No performance overhead on hot code paths**
+
+JAVA Vectors used delegation and abstraction heavily throughout the object
+hierarchy. The performance critical get/set methods of vectors went through
+a chain of function calls back and forth between different objects before
+doing meaningful work. We also evaluated the usage of branches in vector
+APIs and reimplemented some of them by avoiding branches completely.
+
+We took inspiration from how the JAVA memory code in ArrowBuf works. For
+all the performance critical methods, ArrowBuf bypasses all the netty object
+hierarchy, grabs the target virtual address and directly interacts with
+the memory.
+
+There were cases where branches could be avoided all together.
+
+In case of Nullable vectors, we were doing multiple checks to confirm if
+the value at a given position in the vector is NULL or not.
Review comment:
NULL -> null?
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> Blog post on recent improvements/changes in JAVA Vectors
> --------------------------------------------------------
>
> Key: ARROW-1922
> URL: https://issues.apache.org/jira/browse/ARROW-1922
> Project: Apache Arrow
> Issue Type: Task
> Components: Java - Vectors
> Reporter: Siddharth Teotia
> Assignee: Siddharth Teotia
> Labels: pull-request-available
>
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