The index.query.default_field setting in Elasticsearch controls which field or fields are searched by default when a query string doesn't specify a particular field.
- Default value: ["*"]
- Possible values: A string or an array of strings representing field names
- Recommendations: Configure this setting based on your index mapping and search requirements
By default, Elasticsearch searches all fields in the index. However, you can use this setting to limit the search to specific fields, which can improve query performance and relevance.
Example
To set the default search fields to "title" and "content":
PUT /my_index/_settings
{
"index.query.default_field": ["title", "content"]
}
This change would make queries search only in the "title" and "content" fields by default, potentially improving search performance and accuracy for your specific use case.
Common Issues and Misuses
- Setting too many fields can slow down queries
- Excluding important fields may lead to missed search results
- Not updating this setting when index mapping changes
Do's and Don'ts
Do's:
- Regularly review and update this setting as your index evolves
- Use an array of field names for multiple default fields
- Consider using field-specific boosts in your queries for fine-tuned relevance
Don'ts:
- Don't set this to fields that aren't present in your mapping
- Avoid including fields with large amounts of text if not necessary
- Don't rely solely on this setting for query optimization; consider other factors like proper mapping and query structure
Frequently Asked Questions
Q: How does index.query.default_field affect wildcard queries?
A: The setting applies to wildcard queries as well. If specified, wildcard queries will only search within the default fields unless explicitly overridden in the query.
Q: Can I use index.query.default_field with nested fields?
A: Yes, you can include nested fields in the default_field setting. Use dot notation to specify nested fields, e.g., "user.name".
Q: What happens if I set index.query.default_field to an empty array?
A: Setting it to an empty array is equivalent to searching no fields by default. This might cause queries without field specifications to return no results.
Q: How does this setting interact with the _all field?
A: The _all field is deprecated in newer versions of Elasticsearch. index.query.default_field is the recommended way to achieve similar functionality with more control.
Q: Can I change index.query.default_field on a per-query basis?
A: No, this is an index-level setting. For per-query control, specify the fields in your query or use a multi_match query type.
