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Manage Indexes

On this page

  • Indexes Tab
  • Create an Index
  • Hide or Unhide an Index
  • Drop an Index
  • Limitations

Indexes are special data structures that improve query performance. Indexes store a portion of a collection's data in an easy-to-traverse form. The index stores the value of a specific field or set of fields, ordered by the value of the field.

To improve query performance, build indexes on fields that appear often in queries and for all operations that sort by a field.

  • Queries on an indexed field can use the index to limit the number of documents that must be scanned to find matching documents.

  • Sort operations on an indexed field can return documents pre-sorted by the index.

To learn more about indexes, see Indexes.

Note

Considerations

Indexes have some negative performance impact on write operations. For collections with high write-to-read ratio, indexes are expensive since each insert must also update any indexes. For a detailed list of considerations for indexes, see Operational Considerations for Indexes.

The Indexes tab lists the existing indexes for a collection.

To access the Indexes tab for a collection, click on the collection on the left hand pane and select the Indexes tab.

Indexes view

For each index, Compass displays the following information:

Name and Definition
The name of the index and keys.
Type
Regular, text, geospatial or hashed index.
Size
How large the index is.
Usage
Number of times the index has been used in a lookup since the time the index was created or the last server restart.
Properties
Any special properties (such as uniqueness, partial) of the index.
1

From the Indexes tab, click the Create Index button.

2
  1. Specify an index key.

    • To specify an existing document field as an index key, select the field from the dropdown list.

    • To specify a field that does not exist in any document as an index key, enter the field name in the input box.

    • To create a compound index, click the icon next to the index type dropdown.

  2. Use the dropdown to the right of each field name to specify the index type. You can specify one of the following types:

    • Ascending

    • Descending

    • 2dsphere

    • Text

Tip

See also:

To learn how to specify a wildcard index, see Create a Wildcard Index.

3

Compass supports the following index options:

Option
Description
More Information
Create unique index
Ensure that the indexed fields do not store duplicate values.
Index name
Specify a name for the index.
Create a TTL index
Delete documents automatically after a specified number of seconds since the indexed field value.
Partial filter expression

Index only the documents which match the specified filter expression.

Example

The following partial filter expression only indexes documents where the timezone field exists:

{ "timezone": { "$exists": true } }
Use custom collation
Create a custom collation for the index by typing or pasting the collation document in the text box.
Wildcard projection (New in MongoDB 4.2)

Support unknown or arbitrary fields which match the specified projection in the index. To use a wildcard projection, set your index field name to $**. This directs Compass to use all fields in the document (excluding _id).

Example

Consider the following wildcard projection document:

{
"product_attributes.elements" : 1,
"product_attributes.resistance" : 1
}

If your index field name is $**, your index only includes the values of the fields in that projection.

4

Atlas Search indexes let you query data in Atlas Search. For more information, see Create and Manage an Atlas Search Index.

Atlas Vector Search indexes enable you to index vector data and other data types, which facilitates semantic searches on the indexed fields. For more information, see Create an Atlas Vector Search Index.

New in version v4.2.

You can create wildcard indexes to support queries against unknown or arbitrary fields. To create a wildcard index in Compass, manually type the wildcard index field (<field>.$**) into the Select a field name input.

Example

Consider a collection where documents contain a userMetadata object. The fields within the userMetadata object may vary between documents.

You can create a wildcard index on userMetadata to account for all potential fields within the object. Type the following into the Select a field name input:

userMetadata.$**

Specify a type (ascending or descending) for your wildcard index, then click Create Index.

Compass shows the type of your new index as Wildcard.

You can hide an index from the query planner to evaluate the potential impact of dropping an index without actually dropping the index.

1

From the Indexes tab, hover over the index you want to hide.

2

Click the closed-eye icon on the right that appears when you hover over your selected index.

3

In the dialog box, confirm the index you want to hide. After you confirm your selection, a Hidden badge appears under the Properties column.

To unhide your index, repeat steps 1-3. After you unhide your index, Compass removes the Hidden badge from the Properties column.

1

From the Indexes tab, to delete an index, click on the trash can icon for that index. A confirmation dialog appears.

2

In the dialog, enter the name of the index to delete.

3
  • Creating, hiding, and dropping indexes is not permitted in MongoDB Compass Readonly Edition.

  • The Indexes tab is not available if you are connected to a Data Lake.

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