Book Image

Mastering Elasticsearch 5.x - Third Edition

By : Bharvi Dixit
Book Image

Mastering Elasticsearch 5.x - Third Edition

By: Bharvi Dixit

Overview of this book

Elasticsearch is a modern, fast, distributed, scalable, fault tolerant, and open source search and analytics engine. Elasticsearch leverages the capabilities of Apache Lucene, and provides a new level of control over how you can index and search even huge sets of data. This book will give you a brief recap of the basics and also introduce you to the new features of Elasticsearch 5. We will guide you through the intermediate and advanced functionalities of Elasticsearch, such as querying, indexing, searching, and modifying data. We’ll also explore advanced concepts, including aggregation, index control, sharding, replication, and clustering. We’ll show you the modules of monitoring and administration available in Elasticsearch, and will also cover backup and recovery. You will get an understanding of how you can scale your Elasticsearch cluster to contextualize it and improve its performance. We’ll also show you how you can create your own analysis plugin in Elasticsearch. By the end of the book, you will have all the knowledge necessary to master Elasticsearch and put it to efficient use.
Table of Contents (13 chapters)

Built-in functions under the function score query


The following are the built-in functions available to be used with the function_score query:

  • The weight function

  • The field_value_factor function

  • The script_score function

  • Decay functions - linear, exp, gauss

Let's look at them one by one.

The weight function

The weight function allows you to apply a simple boost to each document without the boost being normalized: a weight of 2 results in 2 * _score. For example:

curl -XGET "http://localhost:9200/library/_search" -d' 
{ 
  "query": { 
    "function_score": { 
      "query": { 
        "match": { 
          "tags": "novel" 
        } 
      }, 
      "functions": [ 
        { 
          "filter": { 
            "term": { 
              "tags": "classics" 
            } 
          }, 
          "weight": 2 
        } 
      ], 
      "boost_mode": "replace" 
    } 
  } 
}'

The preceding query will match all the books which belong to the novel category, but will give a higher score to books that also...