Find in mongodb command
There are two ways to find an item from the MongoDB database. One is through MongoDB find method and the other is through findOne method. MongoDB find method fetches the document in a collection and returns the cursor for the documents matching the criteria requested by the user. The syntax for mongodb find method is as follows db. For example: db.
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Executes a query and returns the first batch of results and the cursor id, from which the client can construct a cursor. Rather than run the find command directly, you can use the db. Changed in version 4. Use the maxTimeMS option instead. The find command has the following syntax:. The projection specification to determine which fields to include in the returned documents. Index specification. Specify either the index name as a string or the index key pattern. If specified, then the query system will only consider plans using the hinted index.
The number of documents to return in the first batch. Defaults to A batchSize of 0 means that the cursor will be established, but no documents will be returned in the first batch.
Unlike the previous wire protocol version, a batchSize of 1 for the find command does not close the cursor. The cumulative time limit in milliseconds for processing operations on the cursor.
MongoDB aborts the operation at the earliest following interrupt point. When specifying linearizable read concern , always use maxTimeMS in case a majority of data bearing members are unavailable. Specifies the read concern.
Starting in MongoDB 3. For more formation on the read concern levels, see Read Concern Levels. The getMore command uses the readConcern level specified in the originating find command. The exclusive upper bound for a specific index. See cursor. Starting in MongoDB 4. The inclusive lower bound for a specific index. To use oplogReplay , the find field must refer to a capped collection and you must provide a filter option comparing the ts document field to a timestamp using one of the following comparison operators:.
For example, the following command replays documents from the data capped collection with a timestamp later than or equal to January 1st, UTC:. Changed in version 3. For queries against a sharded collection, allows the command or subsequent getMore commands to return partial results, rather than an error, if one or more queried shards are unavailable.
Specifies the collation to use for the operation. Collation allows users to specify language-specific rules for string comparison, such as rules for lettercase and accent marks. When specifying collation, the locale field is mandatory; all other collation fields are optional. For descriptions of the fields, see Collation Document. If the collation is unspecified but the collection has a default collation see db. If no collation is specified for the collection or for the operations, MongoDB uses the simple binary comparison used in prior versions for string comparisons.
You cannot specify multiple collations for an operation. For example, you cannot specify different collations per field, or if performing a find with a sort, you cannot use one collation for the find and another for the sort. The command returns a document that contains the cursor information, including the cursor id and the first batch of documents. For example, the following document is returned when run against a sharded collection:.
In addition to the aforementioned find -specific fields, the db. See db. For cursors created inside a session, you cannot call getMore outside the session. Similarly, for cursors created outside of a session, you cannot call getMore inside a session. For operations not explicitly associated with a session i. If a session is idle for longer than 30 minutes, the MongoDB server marks that session as expired and may close it at any time.
When the MongoDB server closes the session, it also kills any in-progress operations and open cursors associated with the session. For operations that return a cursor, if the cursor may be idle for longer than 30 minutes, issue the operation within an explicit session using Session. See Session Idle Timeout for more information. In most cases, multi-document transaction incurs a greater performance cost over single document writes, and the availability of multi-document transactions should not be a replacement for effective schema design.
For many scenarios, the denormalized data model embedded documents and arrays will continue to be optimal for your data and use cases. That is, for many scenarios, modeling your data appropriately will minimize the need for multi-document transactions. For additional transactions usage considerations such as runtime limit and oplog size limit , see also Production Considerations. The following command runs the find command filtering on the rating field and the cuisine field. The command sorts the documents in the result set by the name field and limits the result set to 5 documents.
To override the default read concern level of "local" , use the readConcern option. The following operation on a replica set specifies a read concern of "majority" to read the most recent copy of the data confirmed as having been written to a majority of the nodes. To use read concern level of "majority" , replica sets must use WiredTiger storage engine. You can disable read concern "majority" for a deployment with a three-member primary-secondary-arbiter PSA architecture; however, this has implications for change streams in MongoDB 4.
For more information, see Disable Read Concern Majority. Regardless of the read concern level, the most recent data on a node may not reflect the most recent version of the data in the system. A readConcern can be specified for the mongo shell method db.
For more information on available read concerns, see Read Concern. The following operation runs the find command with the collation specified:. The mongo shell provides the cursor. Driver Compatibility Changes. Tip Rather than run the find command directly, you can use the db. The query predicate.
If unspecified, then all documents in the collection will match the predicate. The sort specification for the ordering of the results. Tip When specifying linearizable read concern , always use maxTimeMS in case a majority of data bearing members are unavailable.
For example, the following document is returned when run against a sharded collection: copy. For cursors created outside of a transaction, you cannot call getMore inside the transaction.
For cursors created in a transaction, you cannot call getMore outside the transaction. Important In most cases, multi-document transaction incurs a greater performance cost over single document writes, and the availability of multi-document transactions should not be a replacement for effective schema design.
See also Driver Compatibility Changes. The name of the collection or view to query. The maximum number of documents to return.
If unspecified, then defaults to no limit. A limit of 0 is equivalent to setting no limit. A comment to attach to the query to help interpret and trace query profile data. This is the default read concern level for read operations against primary and read operations against secondaries when associated with causally consistent sessions. This is the default for reads against secondaries when when not associated with causally consistent sessions.
Available for replica sets that use WiredTiger storage engine. Available for read operations on the primary only. If true, returns only the index keys in the resulting documents. Default value is false.
If returnKey is true and the find command does not use an index, the returned documents will be empty. Determines whether to return the record identifier for each document. Returns a tailable cursor for a capped collections. Use in conjunction with the tailable option to block a getMore command on the cursor temporarily if at the end of data rather than returning no data.
After a timeout period, find returns as normal. Prevents the server from timing out idle cursors after an inactivity period 10 minutes. New in version 3. Contains the cursor information, including the cursor id and the firstBatch of documents. Indicates whether the command has succeeded 1 or failed 0.
MongoDB Query Document using find() with Example
The method of fetching or getting data from a MongoDB database is carried out by using queries. MongoDB provides a function called db. During the course of this tutorial, you will see how this function is used in various ways to achieve the purpose of document retrieval. Basic query operations The basic query operations cover the simple operations such as getting all of the documents in a MongoDB collection.
This page documents the mongo shell method, and does not refer to the MongoDB Node. Selects documents in a collection or view and returns a cursor to the selected documents. The projection parameter determines which fields are returned in the matching documents. The projection parameter takes a document of the following form:.
In MongoDB we use the find and findOne methods to find data in a collection. To select data from a collection in MongoDB, we can use the findOne method. The findOne method returns the first occurrence in the selection. The first parameter of the findOne method is a query object. In this example we use an empty query object, which selects all documents in a collection but returns only the first document. To select data from a table in MongoDB, we can also use the find method. The first parameter of the find method is a query object. In this example we use an empty query object, which selects all documents in the collection. The second parameter of the find method is the projection object that describes which fields to include in the result. Return the fields "name" and "address" of all documents in the customers collection:.
Executes a query and returns the first batch of results and the cursor id, from which the client can construct a cursor. Rather than run the find command directly, you can use the db. Changed in version 4. Use the maxTimeMS option instead. The find command has the following syntax:.
You can retrieve previous commands issued in the mongo shell with the up and down arrow keys. The mongo shell can be started with numerous options. See mongo shell page for details on all available options.
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