db.coleção.explain() (método mongosh)

Parâmetros

The db.collection.explain() method has the following parameter:

Modos de Verbosidade

The behavior of db.collection.explain() and the amount of information returned depend on the verbosity mode.

Operações de explicação e gravação

For write operations, db.collection.explain() returns information about the write operation that would be performed but does not actually modify the database.

Restrições

You cannot run the explain command/db.collection.explain() in executionStats mode or allPlansExecution mode for an aggregation pipeline that contains the $out stage. Instead, you can either:

• executar a explicação no modo queryPlanner ou

• executar a explicação no modo executionStats ou no modo allPlansExecution, mas sem o estágio $out para retornar informações para os estágios que precedem o estágio $out.

explain() Mecânica

The db.collection.explain() method wraps the explain command and is the preferred way to run explain.

db.collection.explain().find() is similar to db.collection.find().explain() with the following key differences:

• The db.collection.explain().find() construct allows for the additional chaining of query modifiers. For list of query modifiers, see db.collection.explain().find().help().

• The db.collection.find().explain() returns the explain() information on the query plan.

db.collection.explain().aggregate() is equivalent to passing the explain option to the db.collection.aggregate() method.

help()

To see the list of operations supported by db.collection.explain(), run:

db.collection.explain().help()

db.collection.explain().find() returns a cursor, which allows for the chaining of query modifiers. To see the list of query modifiers supported by db.collection.explain().find() as well as cursor-related methods, run:

db.collection.explain().find().help()

You can chain multiple modifiers to db.collection.explain().find(). For an example, see Explain find() with Modifiers.

queryPlanner Modo

By default, db.collection.explain() runs in "queryPlanner" verbosity mode.

The following example runs db.collection.explain() in "queryPlanner" verbosity mode to return the query planning information for the specified count() operation:

db.products.explain().count( { quantity: { $gt: 50 } } )

executionStats Modo

The following example runs db.collection.explain() in "executionStats" verbosity mode to return the query planning and execution information for the specified find() operation:

db.products.explain("executionStats").find(
   { quantity: { $gt: 50 }, category: "apparel" }
)

allPlansExecution Modo

The following example runs db.collection.explain() in "allPlansExecution" verbosity mode. db.collection.explain() returns the queryPlanner and executionStats for all considered plans for the specified findAndModify() operation:

db.products.explain( "allPlansExecution" ).findAndModify( {
   query: { name: "Tom", state: "active", rating: { $gt: 10 } },
   sort: { rating: 1 },
   update: { $inc: { score: 1 } }
} )

Explique find() com modificadores

db.collection.explain().find() construct allows for the chaining of query modifiers. For example, the following operation provides information on the find() method with sort() and hint() query modifiers.

db.products.explain("executionStats").find(
   { quantity: { $gt: 50 }, category: "apparel" }
).sort( { quantity: -1 } ).hint( { category: 1, quantity: -1 } )

For a list of query modifiers available, run the following in mongosh:

db.collection.explain().find().help()