which command will be accustomed offer varied data on the query plans employed by a mongodb query?

View answer

The explain command will be used for this data. The attainable modes are: 'queryPlanner', 'executionStats', and 'allPlansExecution'.

Yes. The V8 JavaScript engine superimposed in a pair of.4 permits multiple JavaScript operations to run at identical time.

can you run multiple javascript operations during a single mongod instance?

View answer

Yes. The V8 JavaScript engine superimposed in a pair of.4 permits multiple JavaScript operations to run at identical time.

what is gridfs?

View answer

GridFS could be a specification for storing and retrieving files that exceed the BSON-document size limit of 16MB. rather than storing a enter one document, GridFS divides a file into components, or chunks, and stores every of these chunks as a separate document.

how will concurrency have an effect on duplicate sets primary?

View answer

In replication, once MongoDB writes to a collection on the primary, MongoDB conjointly writes to the primary's oplog, that may be a special collection within the native database. Therefore, MongoDB should lock both the collection's database and also the local database.

can one mongodb operation lock more than one databases? if affirmative, how?

View answer

Yes. Operations like copyDatabase, repairDatabase, etc. will lock more than onne databases concerned.

how are you able to isolate your cursors from intervening with the write operations?

View answer

You can use the snapshot technique on a cursor to isolate the operation for a awfully specific case. snapshot traverses the index on the help field and guarantees that the query can come each document no over once.

how will mongodb offer concurrency?

View answer

MongoDB uses reader-writer locks that permit coincidental readers shared access to a resource, like a database or collection, however provide exclusive access to one write operation.

can you assemble the cache size for wiredtiger? how?

View answer

For the WiredTiger storage engine, you'll specify the utmost size of the cache that WiredTiger can use for all data. this will be done exploitation storage.wiredTiger.engineConfig.cacheSizeGB possibility.

can you put together the cache size for mmapv1? how?

View answer

No. MMAPv1 doesn't enable configuring the cache size.

how does journaling add mongodb?

View answer

When running with journaling, MongoDB stores and applies write operations in memory and within the on-disk journal before the changes are present within the data files on disk. Writes to the journal ar atomic, guaranteeing the consistency of the on-disk journal files. With journaling enabled, MongoDB creates a journal directory within the directory defined by dbPath, that is /data/db by default.

Mention the command to visualize whether or not you're on the master server or not. db.isMaster

what is the role of a profiler in mongodb? wherever will the writes all the data?

View answer

The database profiler collects fine grained data concerning MongoDB write operations, cursors, database commands on a running mongod instance. you'll alter identification on a per-database or per-instance basis.

The database profiler writes all the data it collects to the system.profilecollection, that could be a capped collection.

which are the 2 storage engines utilized by mongodb?

View answer

MongoDB uses MMAPv1 and WiredTiger.

what is a storage engine in mongodb

View answer

A storage engine is that the a part of a database that's answerable for managing however data is stored on disk. for instance, one storage engine may supply higher performance for read-heavy workloads, and another may support a higher-throughput for write operations.

why mongodb isn't most popular over a 32-bit system?

View answer

When running a 32-bit build of MongoDB, the whole storage size for the server, together with data and indexes, is a pair of gigabytes. For this reason, don't deploy MongoDB to production on 32-bit machines.

If you are running a 64-bit build of MongoDB, there is nearly no limit to storage size.

when ought to we tend to infix one document among another in mongodb?

View answer

You should think about embedding documents for: 'contains' relationships between entities One-to-many relationships Performance reasons

why are mongodb data files massive in size?

View answer

MongoDB preallocates data files to order house and avoid filing system fragmentation after you setup the server.

what are primary and secondary duplicate sets?

View answer

Primary and master nodes ar the nodes that may accept writes. MongoDB's replication is 'single-master:' only 1 node will settle for write operations at a time.

Secondary and slave nodes ar read-only nodes that replicate from the first.

By default, MongoDB writes and reads knowledge from each primary and secondary reproduction sets. True or False. False. MongoDB writes knowledge solely to the first reproduction set.

what is replication in mongodb? justify.

View answer

Replication is that the method of synchronizing data across multiple servers. Replication provides redundancy and will increase data availableness. With multiple copies of data on totally different database servers, replication protects a info from the loss of one server. Replication conjointly permits you to get over hardware failure and repair interruptions.

what is sharding in mongodb? justify.

View answer

Sharding may be a technique for storing data across multiple machines. MongoDB uses sharding to support deployments with terribly massive knowledge sets and high output operations.

what is aggregation in mongodb?

View answer

Aggregations operations process data records and come back computed results. Aggregation operations cluster values from multiple documents along, and can perform a variety of operations on the grouped knowledge to come back one result. MongoDB provides 3 ways to perform aggregation: the aggregation pipeline, the map-reduce function, and single purpose aggregation strategies and commands.

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