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:

  1. GET /_search
  2. {
  3.   "query": {
  4.     "span_near": {
  5.       "clauses": [
  6.         {
  7.           "span_term": {
  8.             "text": "quick brown"
  9.           }
  10.         },
  11.         {
  12.           "field_masking_span": {
  13.             "query": {
  14.               "span_term": {
  15.                 "text.stems": "fox"
  16.               }
  17.             },
  18.             "field": "text"
  19.           }
  20.         }
  21.       ],
  22.       "slop": 5,
  23.       "in_order": false
  24.     }
  25.   }
  26. }

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.