limit-number-of-items-scanned-for-text-search.txt

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Limit the Number of Entries Scanned
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.. default-domain:: mongodb

.. contents:: On this page
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This tutorial describes how to create indexes to limit the number of
index entries scanned for queries that includes a :query:`$text`
expression and equality conditions.

A collection ``inventory`` contains the following documents:

.. code-block:: javascript

   { _id: 1, dept: "tech", description: "lime green computer" }
   { _id: 2, dept: "tech", description: "wireless red mouse" }
   { _id: 3, dept: "kitchen", description: "green placemat" }
   { _id: 4, dept: "kitchen", description: "red peeler" }
   { _id: 5, dept: "food", description: "green apple" }
   { _id: 6, dept: "food", description: "red potato" }

Consider the common use case that performs text searches by
*individual* departments, such as:

.. code-block:: javascript

   db.inventory.find( { dept: "kitchen", $text: { $search: "green" } } )

To limit the text search to scan only those documents within a specific
``dept``, create a compound index that *first* specifies an
ascending/descending index key on the field ``dept`` and then a
``text`` index key on the field ``description``:

.. code-block:: javascript

   db.inventory.createIndex(
      {
        dept: 1,
        description: "text"
      }
   )

Then, the text search within a particular department
will limit the scan of indexed documents. For example, the following
query scans only those documents with ``dept`` equal to ``kitchen``:

.. code-block:: javascript

   db.inventory.find( { dept: "kitchen", $text: { $search: "green" } } )

.. note::

   .. include:: /includes/fact-compound-index-with-text-restrictions.rst

.. seealso:: :doc:`/core/index-text`