What is execution stats in MongoDB?
executionStats Mode MongoDB runs the query optimizer to choose the winning plan, executes the winning plan to completion, and returns statistics describing the execution of the winning plan. However, executionStats does not provide query execution information for the rejected plans.
What is explain () in MongoDB?
The $explain operator provides information on the query plan. It returns a document that describes the process and indexes used to return the query. This may provide useful insight when attempting to optimize a query. For details on the output, see cursor.
How can you view the execution performance statistics for a query?
To view live query statistics for one query To view the live query execution plan, on the tools menu click the Include Live Query Statistics icon. You can also view access the live query execution plan by right-clicking on a selected query in Management Studio and then click Include Live Query Statistics.
How does MongoDB get execution time?
i see that in mongodb there is a possibility to use this two command:
- db. setProfilingLevel(2)
- and so after the query you can use db. system. profile. find() to see the query execution time and other.
How does MongoDB reduce query execution time?
Reduce query execution time in MongoDB when querying tags in an array
- Only necessary fields are projected which reduced the time by 10-30% depending on the query.
- Tried to reduce the size of each document to only contain necessary and non-empty fields.
- Tried to make tags more selective.
How can you view the execution performance statistics for a query in MongoDB?
Evaluate Performance of Current Operations¶
- Use the Database Profiler to Evaluate Operations Against the Database.
- Use db.currentOp() to Evaluate mongod Operations.
- Use explain to Evaluate Query Performance.
How does MongoDB detect slow queries?
One can identify slow queries in MongoDB by enabling the profiler and configuring it to its some specifications or executing db. currentOp() on a running mongod instance. By looking at the time parameters on the returned result, we can identify which queries are lagging.
How does MongoDB detect long running queries?
The db. currentOp() method reports in-progress operations on your mongod process. In other words, it will return information on all active operations running on your instance. This allows you to quickly identify long-running and/or blocking operations and focus your attention on problematic areas.
How query is executed in MongoDB?
How to Execute Database Query in MongoDB
- use DATABASE_NAME command is used to create database Example: >use hdfc switched to db mydb.
- db command is used to check currently selected database Example: >db mydb.
- show dbs command check all database lists Example: >show dbs local 0.78125GB test 0.23012GB.
Where are MongoDB commands executed?
Connect to MongoDB database Then type mongo command to run the shell. Now you are in the Mongo shell. If you want, you can run the mongo and mongod without the command prompt. To do this, go to the installation location and double click on the mongod and mongo applications.
What query language does MongoDB use?
MQL
MongoDB uses the MongoDB Query Language (MQL), designed for easy use by developers. The documentation compares MQL and SQL syntax for common database operations.
What does the executionstats in MongoDB mean?
The executionStats includes the completed query execution information for the winning plan. If the query optimizer considered more than one plan, executionStats information also includes the partial execution information captured during the plan selection phase for both the winning and rejected candidate plans.
How does the explain function work in MongoDB?
The execution of this explain will not modify data but runs the query predicate of the update operation. For candidate plans, MongoDB returns the execution information captured during the plan selection phase. © MongoDB, Inc 2008-present.
What does completed query execution mean in MongoDB?
For write operations, completed query execution refers to the modifications that would be performed, but does not apply the modifications to the database. Number of documents that match the query condition. nReturned corresponds to the n field returned by cursor.explain () in earlier versions of MongoDB.
How does the query optimizer work in MongoDB?
MongoDB runs the query optimizer to choose the winning plan and executes the winning plan to completion. In “allPlansExecution” mode, MongoDB returns statistics describing the execution of the winning plan as well as statistics for the other candidate plans captured during plan selection.
