Unlike a relational database which has normalized data, the data stored in a NoSQL database is highly denormalised, and each document is independent. However, Elasticsearch provides two features which enable us to run queries whose results depend on the relationship between two separate documents: Nested documents and Parent-child relationships.
This chapter explains the use case for each of these features and the extensions to the interface that allows us to take advantage of these relationships.
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Mapping
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Indexing, retrieving and deleting documents
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Searching
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nested queries
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nested filters
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nested facets
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