Does MongoDB have locks?

Does MongoDB have locks?

MongoDB uses multi-granularity locking [1] that allows operations to lock at the global, database or collection level, and allows for individual storage engines to implement their own concurrency control below the collection level (e.g., at the document-level in WiredTiger).

Is MongoDB multithreaded?

MongoDB Realm enables simple and safe multithreaded code when you follow these three rules: Don’t lock to read: Realm Database’s Multiversion Concurrency Control (MVCC) architecture eliminates the need to lock for read operations. The values you read will never be corrupted or in a partially-modified state.

Is MongoDB update thread-safe?

No, it is not thread-safe as it is not done atomically since MongoDB is not a transactional database, you are supposed to use $inc operator for such need as it allows to increment atomically given fields of given amounts, more details here.

Is there a way to deactivate shardcollection in MongoDB?

MongoDB provides no method to deactivate sharding for a collection after calling shardCollection. Additionally, after shardCollection, you cannot change shard keys or modify the value of any field used in your shard key index.

When to use hashed shard key in MongoDB?

“hashed” to specify a hashed shard key. shard key must be supported by an index. Unless the collection is empty, the index must exist prior to the shardCollection command. If the collection is empty, MongoDB creates the index prior to sharding the collection if the index that can support the shard key does not already exist.

Is there a way to unshard a MongoDB collection?

Once a collection has been sharded, MongoDB provides no method to unshard a sharded collection. While you can change your shard key later, it is important to carefully consider your shard key choice to avoid scalability and perfomance issues. Hashed shard keys use a hashed index or a compound hashed index as the shard key.

Why does MongoDB use multi granularity locking?

MongoDB uses multi-granularity locking [ 1] that allows operations to lock at the global, database or collection level, and allows for individual storage engines to implement their own concurrency control below the collection level (e.g., at the document-level in WiredTiger).