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cursor.readConcern()

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  • Definition
  • Considerations

Definition

cursor.readConcern(level)

Important

mongosh Method

This page documents a mongosh method. This is not the documentation for a language-specific driver, such as Node.js.

For MongoDB API drivers, refer to the language-specific MongoDB driver documentation.

Specify a read concern for the db.collection.find() method.

The readConcern() method has the following form:

db.collection.find().readConcern(<level>)

The readConcern() method has the following parameter:

Parameter
Type
Description
level
string

Read concern level.

Possible read concern levels are:

  • "local". This is the default read concern level for read operations against the primary and secondaries.

  • "available". Available for read operations against the primary and secondaries. "available" behaves the same as "local" against the primary and non-sharded secondaries. The query returns the instance's most recent data.

  • "majority". Available for replica sets that use WiredTiger storage engine.

  • "linearizable". Available for read operations on the primary only.

For more formation on the read concern levels, see Read Concern Levels.

Considerations

Read Your Own Writes

You can use causally consistent sessions to read your own writes, if the writes request acknowledgment.

Linearizable Read Concern Performance

When specifying linearizable read concern, always use maxTimeMS() in case a majority of data bearing members are unavailable.

db.restaurants.find( { _id: 5 } ).readConcern("linearizable").maxTimeMS(10000)

Tip

See also:

Read Concern

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