In Elasticsearch, a mapping is a definition that specifies how a document’s fields should be indexed and stored. A mapping defines the fields and their data types, as well as any custom settings or analysis that should be applied to the fields. Here’s how a mapping works in Elasticsearch:
1. Creation of a mapping: To create a mapping in Elasticsearch, you send a PUT request to the mapping API with the JSON object as the request body. Elasticsearch automatically creates the mapping and associates it with the index.
2. Definition of fields and data types: A mapping defines the fields and their data types, such as text, keyword, date, integer, float, and more. Elasticsearch uses this information to determine how to index and store the data, as well as how to perform searches on the data.
3. Custom settings and analysis: A mapping can also include custom settings and analysis that are applied to the fields. For example, you can specify how text should be analyzed, such as using stemming, stop word removal, or synonym expansion. You can also specify whether a field should be indexed, stored, or both.
4. Updating a mapping: You can update a mapping in Elasticsearch by sending a POST request to the mapping API with the updated JSON object. Elasticsearch automatically updates the mapping and reindexes the data.
5. Mapping templates: Elasticsearch also supports mapping templates, which allow you to define mappings that are automatically applied to new indexes that match a specific pattern. Mapping templates can simplify the process of creating and maintaining mappings across multiple indexes.
6. Management and monitoring of mappings: Elasticsearch provides various tools for managing and monitoring mappings, such as the indices stats API and the cat APIs. These tools allow you to check the health and status of the index, monitor resource usage, and troubleshoot issues.
Overall, mappings are a critical component of Elasticsearch’s architecture, providing the ability to define how data is indexed and searched. By defining mappings in Elasticsearch, you can ensure that your data is indexed and searched in a consistent and efficient manner, and that custom analysis is applied to your text data to improve search accuracy and relevance.