OpenSearch/docs/reference/query-dsl/span-field-masking-query.as...

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[[query-dsl-span-field-masking-query]]
=== Span Field Masking Query
Wrapper to allow span queries to participate in composite single-field span queries by 'lying' about their search field. The span field masking query maps to Lucene's `SpanFieldMaskingQuery`
This can be used to support queries like `span-near` or `span-or` across different fields, which is not ordinarily permitted.
Span field masking query is invaluable in conjunction with *multi-fields* when same content is indexed with multiple analyzers. For instance we could index a field with the standard analyzer which breaks text up into words, and again with the english analyzer which stems words into their root form.
Example:
[source,js]
--------------------------------------------------
GET /_search
{
"query": {
"span_near": {
"clauses": [
{
"span_term": {
"text": "quick brown"
}
},
{
"field_masking_span": {
"query": {
"span_term": {
"text.stems": "fox"
}
},
"field": "text"
}
}
],
"slop": 5,
"in_order": false
}
}
}
--------------------------------------------------
// CONSOLE
Note: as span field masking query returns the masked field, scoring will be done using the norms of the field name supplied. This may lead to unexpected scoring behaviour.