Book Image

Elasticsearch Essentials

Book Image

Elasticsearch Essentials

Overview of this book

With constantly evolving and growing datasets, organizations have the need to find actionable insights for their business. ElasticSearch, which is the world's most advanced search and analytics engine, brings the ability to make massive amounts of data usable in a matter of milliseconds. It not only gives you the power to build blazing fast search solutions over a massive amount of data, but can also serve as a NoSQL data store. This guide will take you on a tour to become a competent developer quickly with a solid knowledge level and understanding of the ElasticSearch core concepts. Starting from the beginning, this book will cover these core concepts, setting up ElasticSearch and various plugins, working with analyzers, and creating mappings. This book provides complete coverage of working with ElasticSearch using Python and performing CRUD operations and aggregation-based analytics, handling document relationships in the NoSQL world, working with geospatial data, and taking data backups. Finally, we’ll show you how to set up and scale ElasticSearch clusters in production environments as well as providing some best practices.
Table of Contents (18 chapters)
Elasticsearch Essentials
Credits
About the Author
Acknowledgments
About the Reviewer
www.PacktPub.com
Preface
Index

Combining search, buckets, and metrics


We can always combine searches, filters bucket aggregations, and metric aggregations to get a more and more complex analysis. Until now, we have seen single levels of aggregations; however, as explained in the aggregation syntax section earlier, an aggregation can contain multiple levels of aggregations within. However, metric aggregations cannot contain further aggregations within themselves. Also, when you run an aggregation, it is executed on all the documents in the index for a document type if specified on a match_all query context, but you can always use any type of Elasticsearch query with an aggregation. Let's see how we can do this in Python and Java clients.

Python example

query = {
  "query": {
    "match": {
      "text": "crime"
    }
  },
  "aggs": {
    "hourly_timeline": {
      "date_histogram": {
        "field": "created_at",
        "interval": "hour"
      },
      "aggs": {
        "top_hashtags": {
          "terms": {
      ...