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DOCSP-41142: Work with Indexes + Single Field Indexes #14
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import com.mongodb.ConnectionString | ||
import com.mongodb.MongoClientSettings | ||
import com.mongodb.client.model.Indexes | ||
import com.mongodb.client.model.Filters | ||
import com.mongodb.client.model.Sorts | ||
import com.mongodb.kotlin.client.MongoClient | ||
import org.bson.codecs.pojo.annotations.BsonId | ||
import org.bson.types.ObjectId | ||
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// start-movie-class | ||
data class Movie( | ||
@BsonId | ||
val id: ObjectId, | ||
val title: String? = "", | ||
val genre: String? = "", | ||
val cast: List<String>? = null, | ||
val plot: String? = "", | ||
) | ||
// end-movie-class | ||
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fun main() { | ||
val uri = "<connection string URI>" | ||
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val settings = MongoClientSettings.builder() | ||
.applyConnectionString(ConnectionString(uri)) | ||
.retryWrites(true) | ||
.build() | ||
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val mongoClient = MongoClient.create(settings) | ||
val database = mongoClient.getDatabase("sample_mflix") | ||
val collection = database.getCollection<Movie>("movies") | ||
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// start-remove-index | ||
collection.dropIndex("_title_") | ||
// end-remove-index | ||
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// start-remove-all-indexes | ||
collection.dropIndexes() | ||
// end-remove-all-indexes | ||
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// start-index-single | ||
collection.createIndex(Indexes.ascending(Movie::title.name)) | ||
// end-index-single | ||
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// start-index-single-query | ||
val filter = Filters.eq(Movie::title.name, "Batman") | ||
val sort = Sorts.ascending(Movie::title.name) | ||
val results = collection.find(filter).sort(sort) | ||
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results.forEach { result -> | ||
println(result) | ||
} | ||
// end-index-single-query | ||
} |
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.. _kotlin-sync-single-field-index: | ||
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==================== | ||
Single-Field Indexes | ||
==================== | ||
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.. contents:: On this page | ||
:local: | ||
:backlinks: none | ||
:depth: 2 | ||
:class: singlecol | ||
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.. facet:: | ||
:name: genre | ||
:values: reference | ||
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.. meta:: | ||
:keywords: index, query, optimization, efficiency | ||
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Overview | ||
-------- | ||
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:manual:`Single-field indexes </core/index-single/>` are indexes with a reference to a | ||
single field within a collection's documents. They improve single field query and sort | ||
performance, and support :manual:`TTL Indexes </core/index-ttl>` that automatically remove | ||
documents from a collection after a certain amount of time or at a specific clock time. | ||
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.. note:: | ||
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The ``_id_`` index is an example of a single-field index. This index is automatically | ||
created on the ``_id`` field when a new collection is created. | ||
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Sample Data | ||
~~~~~~~~~~~ | ||
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The examples in this guide use the ``movies`` collection in the ``sample_mflix`` | ||
database from the :atlas:`Atlas sample datasets </sample-data>`. To learn how to create a | ||
free MongoDB Atlas cluster and load the sample datasets, see the | ||
:atlas:`Get Started with Atlas </getting-started>` guide. | ||
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The documents in this collection are modeled by the following {+language+} data class: | ||
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.. literalinclude:: /includes/indexes/indexes.kt | ||
:start-after: start-movie-class | ||
:end-before: end-movie-class | ||
:language: kotlin | ||
:copyable: | ||
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Create Single-Field Index | ||
------------------------- | ||
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The following example creates an index in ascending order on the ``title`` field: | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Q:Are there options to create an index in any other order other than ascending and descending? S: Clarify/state explicitly that you can create an index in either ascending or descending order. There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Will add to page overview. |
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.. literalinclude:: /includes/indexes/indexes.kt | ||
:start-after: start-index-single | ||
:end-before: end-index-single | ||
:language: kotlin | ||
:copyable: | ||
:dedent: | ||
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The following is an example of a query that is covered by the index created in the preceding code example: | ||
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.. io-code-block:: | ||
:copyable: true | ||
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.. input:: /includes/indexes/indexes.kt | ||
:start-after: start-index-single-query | ||
:end-before: end-index-single-query | ||
:language: kotlin | ||
:dedent: | ||
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.. output:: | ||
:visible: false | ||
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Movie(id=573a1398f29313caabceb515, title=Batman, ...) | ||
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To learn more, see :manual:`Single Field Indexes </core/index-single>` in the {+mdb-server+} manual. | ||
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.. _kotlin-sync-work-with-indexes: | ||
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================= | ||
Work with Indexes | ||
================= | ||
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.. contents:: On this page | ||
:local: | ||
:backlinks: none | ||
:depth: 2 | ||
:class: singlecol | ||
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.. facet:: | ||
:name: genre | ||
:values: reference | ||
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.. meta:: | ||
:keywords: query, optimization, efficiency | ||
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.. toctree:: | ||
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/indexes/single-field-index.txt | ||
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Overview | ||
-------- | ||
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In this guide, you can learn how to use **indexes** with the {+driver-short+}. | ||
Indexes can improve the efficiency of queries and add functionality to querying and | ||
storing documents. | ||
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Without indexes, MongoDB must scan every document in a collection to find the | ||
documents that match each query. These collection scans are slow and can negatively affect | ||
the performance of your application. However, if an appropriate index exists for a query, | ||
MongoDB can use the index to limit the documents it must inspect. | ||
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Operational Considerations | ||
~~~~~~~~~~~~~~~~~~~~~~~~~~ | ||
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To improve query performance, build indexes on fields that appear often in | ||
your application's queries and operations that return sorted results. Each | ||
index that you add consumes disk space and memory when active, so we recommend | ||
that you track index memory and disk usage for capacity planning. In addition, | ||
when a write operation updates an indexed field, MongoDB updates the related | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. S: I see that in the server manual, it talks about how indexes are not always the best when using write operations. I believe that the sentence starting with "In addition, when a write.." is implying that indices can negatively affect write operation performance, but it would be great to make that clearer. |
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index. | ||
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Because MongoDB supports dynamic schemas, applications can query against fields | ||
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whose names are not known in advance or are arbitrary. MongoDB 4.2 introduced | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Q: Is it it necessary to say what version of MongoDB introduced wildcard indexes, or can we just say that wildcard indexes support queries with fields that have arbitrary/unknown names? There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Can reword. |
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:manual:`wildcard indexes </core/index-wildcard/>` to help support these | ||
queries. Wildcard indexes are not designed to replace workload-based index | ||
planning. | ||
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For more information about designing your data model and choosing indexes appropriate for your application, see the | ||
:manual:`Data Modeling and Indexes </core/data-model-operations/#indexes>` guide | ||
in the {+mdb-server+} manual. | ||
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Sample Data | ||
~~~~~~~~~~~ | ||
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The examples in this guide use the ``movies`` collection in the ``sample_mflix`` | ||
database from the :atlas:`Atlas sample datasets </sample-data>`. To learn how to create a | ||
free MongoDB Atlas cluster and load the sample datasets, see the | ||
:atlas:`Get Started with Atlas </getting-started>` guide. | ||
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Create an Index | ||
--------------- | ||
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MongoDB supports several different index types to support querying your data. | ||
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The following pages describe the most common index types and provide sample | ||
code for creating each index type. | ||
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- :ref:`kotlin-sync-single-field-index` | ||
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.. TODO: - :ref:`kotlin-sync-compound-index` | ||
.. TODO: - :ref:`kotlin-sync-atlas-search-index` | ||
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Remove an Index | ||
--------------- | ||
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You can remove any unused index except the default unique index on the | ||
``_id`` field. | ||
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The following sections show how to remove a single index or to remove all | ||
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indexes in a collection. | ||
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Delete a Single Index | ||
~~~~~~~~~~~~~~~~~~~~~ | ||
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Pass an index name to the ``dropIndex()`` method to remove an index from a collection. | ||
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The following example removes an index with the name ``"_title_"`` from the ``movies`` | ||
collection: | ||
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.. literalinclude:: /includes/indexes/indexes.kt | ||
:language: kotlin | ||
:start-after: start-remove-index | ||
:end-before: end-remove-index | ||
:dedent: | ||
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.. note:: | ||
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You cannot remove a single field from a compound text index. You must | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Q: I don't know what a compound text index is; is that information you expect the user to have already going into this page? There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. All types of indexes are slated to receive their own page – this page will link to the compound text index page once it's written. |
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drop the entire index and create a new one to update the indexed | ||
fields. | ||
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Delete All Indexes | ||
~~~~~~~~~~~~~~~~~~ | ||
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Starting with MongoDB 4.2, you can drop all indexes by calling the | ||
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``dropIndexes()`` method on your collection: | ||
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.. literalinclude:: /includes/indexes/indexes.kt | ||
:language: kotlin | ||
:start-after: start-remove-all-indexes | ||
:end-before: end-remove-all-indexes | ||
:dedent: | ||
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API Documentation | ||
~~~~~~~~~~~~~~~~~ | ||
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To learn more about any of the methods or types discussed in this | ||
guide, see the following API documentation: | ||
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- `createIndex() <{+api+}/mongodb-driver-kotlin-sync/com.mongodb.kotlin.client/-mongo-collection/create-index.html>`__ | ||
- `createIndexes() <{+api+}/mongodb-driver-kotlin-sync/com.mongodb.kotlin.client/-mongo-collection/create-indexes.html>`__ | ||
- `dropIndex() <{+api+}/mongodb-driver-kotlin-sync/com.mongodb.kotlin.client/-mongo-collection/drop-index.html>`__ | ||
- `dropIndexes() <{+api+}/mongodb-driver-kotlin-sync/com.mongodb.kotlin.client/-mongo-collection/drop-indexes.html>`__ |
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