MongoDB Full and Partial Text Search

Question

Env:

• MongoDB (3.2.0) with mongos

---

Collection:

• users

---

Text Index creation:

  BasicDBObject keys = new BasicDBObject();
  keys.put("name","text");

  BasicDBObject options = new BasicDBObject();
  options.put("name", "userTextSearch");
  options.put("unique", Boolean.FALSE);
  options.put("background", Boolean.TRUE);

  userCollection.createIndex(keys, options); // using MongoTemplate

---

Document:

• {"name":"LEONEL"}

---

Queries:

• db.users.find( { "$text" : { "$search" : "LEONEL" } } ) => FOUND
• db.users.find( { "$text" : { "$search" : "leonel" } } ) => FOUND (search caseSensitive is false)
• db.users.find( { "$text" : { "$search" : "LEONÉL" } } ) => FOUND (search with diacriticSensitive is false)
• db.users.find( { "$text" : { "$search" : "LEONE" } } ) => FOUND (Partial search)
• db.users.find( { "$text" : { "$search" : "LEO" } } ) => NOT FOUND (Partial search)
• db.users.find( { "$text" : { "$search" : "L" } } ) => NOT FOUND (Partial search)

Any idea why I get 0 results using as query "LEO" or "L"?

Regex with Text Index Search is not allowed.

db.getCollection('users')
     .find( { "$text" : { "$search" : "/LEO/i", 
                          "$caseSensitive": false, 
                          "$diacriticSensitive": false }} )
     .count() // 0 results

db.getCollection('users')
     .find( { "$text" : { "$search" : "LEO", 
                          "$caseSensitive": false, 
                          "$diacriticSensitive": false }} )
.count() // 0 results

---

MongoDB Documentation:

• Text Search
• $text
• Text Indexes
• Improve Text Indexes to support partial word match

Answer 1

As at MongoDB 3.4, the text search feature is designed to support case-insensitive searches on text content with language-specific rules for stopwords and stemming. Stemming rules for supported languages are based on standard algorithms which generally handle common verbs and nouns but are unaware of proper nouns.

There is no explicit support for partial or fuzzy matches, but terms that stem to a similar result may appear to be working as such. For example: "taste", "tastes", and tasteful" all stem to "tast". Try the Snowball Stemming Demo page to experiment with more words and stemming algorithms.

Your results that match are all variations on the same word "LEONEL", and vary only by case and diacritic. Unless "LEONEL" can be stemmed to something shorter by the rules of your selected language, these are the only type of variations that will match.

If you want to do efficient partial matches you'll need to take a different approach. For some helpful ideas see:

• Efficient Techniques for Fuzzy and Partial matching in MongoDB by John Page
• Efficient Partial Keyword Searches by James Tan

There is a relevant improvement request you can watch/upvote in the MongoDB issue tracker: SERVER-15090: Improve Text Indexes to support partial word match.