MongoEngine - Text search

MongoDB supports use of query operators that can perform text search on a string content. As described earlier, to set a text index prefix name of index with $ symbol. For a text index, the weight of an indexed field denotes the significance of the field relative to the other indexed fields in terms of the text search score. You can also specify default language in meta dictionary of the class.

List of supported languages can be found at https://docs.mongodb.com/manual/reference/text-search-languages/ MongoEngine API consists of search_text() method for QuerySet object. The string to be searched in indexed fields is given as argument.

In the following example, we first define a Document class called lang with two string fields, name of language and its features. We also create indexes on both fields with respective weights.

from mongoengine import *
con=connect('newdb')

class lang (Document):
   name=StringField()
   features=StringField()
   meta = {'indexes': [
      {'fields': ['$name', "$features"],
         'default_language': 'english',
         'weights': {'name': 2, 'features': 10}
      }]
   }

l1=lang()
l1.name='C++'
l1.features='Object oriented language for OS development'
l1.save()
l2=lang()
l2.name='Python'
l2.features='dynamically typed and object oriented for data science, AI and ML'
l2.save()
l3=lang()
l3.name='HTML'
l3.features='scripting language for web page development'
l3.save()

In order to perform search for word ‘oriented’, we employ search_text() method as follows −

docs=lang.objects.search_text('oriented')
for doc in docs:
   print (doc.name)

Output of the above code will be names of languages in whose description the word ‘oriented’ occurs (‘Python and ‘C++’ in this case).