Overview of Fields
Fields provide a convenient mechanism for querying a portion of the database based on XML element QNames or JSON property names. Unlike collections or directories, which enable you to query portions of a database based on document URIs, fields enable you to query portions of a database based on XML element and JSON property names. This offers extra convenience for the application developer, and also offers a performance boost over other methods of querying a portion of the database. Fields are extremely useful when you have content in one or more elements or JSON properties that you want to query simply and efficiently as a single unit.
Field query is similar to word query (in its default configuration, with everything included), but instead of querying everything in the database, fields query only what is configured for the specified field. Fields have their own set of indexes, independent of the database indexes. Because fields have their own indexes, and a field is typically a small subset of the whole database, querying a field is often more efficient than querying those same XML element or JSON properties directly (with cts:word-query, for example).
Also, because fields have their own sets of indexes, relevance for fields is calculated based on the content in the field, not based on all of the content in the database. This provides finer-grain relevance for field searches than for other searches.
You can use fields to create portions of the content that you might want to query as a single unit. Additionally, you can configure a field with indexing options over and above the ones configured in the database. For example, consider a database containing many technical articles, each article containing a brief abstract. You might want to build an application that allows greater capabilities for searching through the abstracts than for searching through the rest of the articles. Assume your main content does not have wildcard indexes, but you want to be able to search through the abstracts using wildcard searches. You can create a field on the abstract, and then add wildcard indexes to that field. Because the field represents only a relatively small percentage of the content, the relative cost of the extra indexing is small.
Indexing of JSON and XML content differs slightly. This introduces differences in the behavior of field value queries and field range queries over the two types of content. For details, see How Field Queries Differ Between JSON and XML in the Application Developer’s Guide.