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  • Book Overview & Buying Mastering Elasticsearch
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Mastering Elasticsearch

Mastering Elasticsearch - Second Edition

By : Marek Rogozinski
4.3 (9)
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Mastering Elasticsearch

Mastering Elasticsearch

4.3 (9)
By: Marek Rogozinski
Buy this Book

Overview of this book

This book is for Elasticsearch users who want to extend their knowledge and develop new skills. Prior knowledge of the Query DSL and data indexing is expected.
Table of Contents (11 chapters)
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Preface
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Preface
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What this book covers
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What you need for this book
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Who this book is for
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Conventions
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Reader feedback
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Customer support
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1
1. Introduction to Elasticsearch
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1. Introduction to Elasticsearch
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Introducing Apache Lucene
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Introducing Elasticsearch
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The story
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Summary
2
2. Power User Query DSL
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2. Power User Query DSL
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Default Apache Lucene scoring explained
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Query rewrite explained
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Query templates
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Handling filters and why it matters
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Choosing the right query for the job
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Summary
3
3. Not Only Full Text Search
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3. Not Only Full Text Search
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Query rescoring
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Controlling multimatching
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Significant terms aggregation
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Documents grouping
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Relations between documents
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Scripting changes between Elasticsearch versions
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Summary
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4. Improving the User Search Experience
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4. Improving the User Search Experience
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Correcting user spelling mistakes
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Improving the query relevance
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Summary
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5. The Index Distribution Architecture
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5. The Index Distribution Architecture
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Choosing the right amount of shards and replicas
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Routing explained
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Altering the default shard allocation behavior
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Query execution preference
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Summary
6
6. Low-level Index Control
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6. Low-level Index Control
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Altering Apache Lucene scoring
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Choosing the right directory implementation – the store module
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NRT, flush, refresh, and transaction log
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Segment merging under control
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When it is too much for I/O – throttling explained
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Understanding Elasticsearch caching
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Summary
7
7. Elasticsearch Administration
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7. Elasticsearch Administration
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Discovery and recovery modules
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The human-friendly status API – using the Cat API
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Backing up
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Federated search
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Summary
8
8. Improving Performance
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8. Improving Performance
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Using doc values to optimize your queries
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Knowing about garbage collector
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Benchmarking queries
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Very hot threads
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Scaling Elasticsearch
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Summary
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9. Developing Elasticsearch Plugins
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9. Developing Elasticsearch Plugins
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Creating the Apache Maven project structure
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Understanding the basics
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Creating custom REST action
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Creating the custom analysis plugin
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Summary
10
Index
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Index

Query rescoring

One of the great features provided by Elasticsearch is the ability to change the ordering of documents after they were returned by a query. Actually, Elasticsearch does a simple trick—it recalculates the score of top matching documents, so only part of the document in the response is reordered. The reasons why we want to do that can vary. One of the reasons may be performance—for example, calculating target ordering is very costly because scripts are used and we would like to do this on the subset of documents returned by the original query. You can imagine that rescore gives us many great opportunities for business use cases. Now, let's look at this functionality and how we can benefit from using it.

What is query rescoring?

Rescore in Elasticsearch is the process of recalculating the score for a defined number of documents returned by the query. This means that Elasticsearch first takes N documents for a given query (or the post_filter phase) and calculates their score using...

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Mastering Elasticsearch
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