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How to Index String Fields

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  • Review the Limitations for the string Type
  • Define the Index for the string Type
  • Configure string Field Properties
  • Try an Example for the string Type

You can use the Atlas Search string type to index string fields. You can use the Atlas Search phrase, queryString, span, text, wildcard, regex, and moreLikeThis operators to query fields indexed as the string type.

If you enable dynamic mappings, Atlas Search automatically indexes fields of type string. You can use the Visual Editor or the JSON Editor in the Atlas UI to index fields as the string type.

Review the Limitations for the string Type

You can't use the Atlas Search string type to index fields for facet or autocomplete queries. You can't use the string type to index fields for sorting Atlas Search results. Instead, you must use static mappings to index the string fields as the following types:

Atlas Search won't index string fields that exceed 32766 bytes in size.

Define the Index for the string Type

To define the index for the string type, choose your preferred configuration method in the Atlas UI and then select the database and collection.

Configure string Field Properties

The Atlas Search string type takes the following parameters:

Option
Type
Necessity
Description
Default
type
string
Required
Human-readable label that identifies this field type. Value must be string.
analyzer
string
Optional

Name of a built-in or custom analyzer to use for indexing the field. If you don't specify a value, inherits an analyzer by default in the following order:

  1. The analyzer option for the index if specified.

  2. The lucene.standard analyzer.

searchAnalyzer
string
Optional

Analyzer to use when querying the field. If you don't specify a value, inherits an analyzer by default in the following order:

  1. The analyzer option for this field if specified.

  2. The searchAnalyzer option for the index if specified.

  3. The analyzer option for the index if specified.

  4. The lucene.standard analyzer.

indexOptions
string
Optional

Amount of information to store for the indexed field. Value can be one of the following:

  • docs - Only indexes documents. The frequency and position of the indexed term are ignored. Only a single occurence of the term is reflected in the score.

  • freqs - Only indexes documents and term frequency. The position of the indexed term is ignored.

  • positions - Indexes documents, term frequency, and term positions.

  • offsets - (Default) Indexes documents, term frequency, term positions, and term offsets. This option is required for highlight.

offsets
store
boolean
Optional

Flag that indicates whether to store the exact document text as well as the analyzed values in the index. Value can be true or false. The value for this option must be true for highlight.

Note

To reduce the index size and performance footprint, we recommend setting store to false. To learn more, see Atlas Search Index Performance.

true
ignoreAbove
int
Optional
Maximum number of characters in the value of the field to index. Atlas Search doesn't index if the field value is greater than the specified number of characters.
multi
String Field Definition
Optional
String field to index with the name of the alternate analyzer specified in the multi object. To learn more about specifying the multi object, see Multi Analyzer and example below.
norms
string
Optional

String that specifies whether to include or omit the field length in the result when scoring. The length of the field is determined by the number of tokens produced by the analyzer for the field. Value can be one of the following:

  • include - to include the field length when scoring.

  • omit - to omit the field length when scoring.

If value is include, Atlas Search uses the length of the field to determine the higher score when scoring. For example, if two documents match an Atlas Search query, the document with the shorter field length scores higher than the document with the longer field length.

If value is omit, Atlas Search ignores the field length when scoring.

include

Try an Example for the string Type

The following index definition example uses the sample_mflix.movies collection. If you have the sample data already loaded on your cluster, you can use the Visual Editor or JSON Editor in the Atlas UI to configure the index. After you select your preferred configuration method, select the database and collection, and refine your index to add field mappings.

←  How to Index ObjectId Values in FieldsHow to Index String Fields For Faceted Search →

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