Elasticsearch: The Definitive Guide

Chapter 12. Structured Search

Structured search is about interrogating data that has inherent structure. Dates, times, and numbers are all structured: they have a precise format that you can perform logical operations on. Common operations include comparing ranges of numbers or dates, or determining which of two values is larger.

Text can be structured too. A box of crayons has a discrete set of colors: red, green, blue. A blog post may be tagged with keywords distributed and search. Products in an ecommerce store have Universal Product Codes (UPCs) or some other identifier that requires strict and structured formatting.

With structured search, the answer to your question is always a yes or no; something either belongs in the set or it does not. Structured search does not worry about document relevance or scoring; it simply includes or excludes documents.

This should make sense logically. A number can’t be more in a range than any other number that falls in the same range. It is either in the range—or it isn’t. Similarly, for structured text, a value is either equal or it isn’t. There is no concept of more similar.

Finding Exact Values

When working with exact values, you will be working with filters. Filters are important because they are very, very fast. Filters do not calculate relevance (avoiding the entire scoring phase) and are easily cached. We’ll talk about the performance benefits of filters later in “All About Caching”, but for now, just keep in mind that you should ...