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How does MongoDB maintain data consistency?
How does MongoDB ensure consistency? MongoDB is consistent by default: reads and writes are issued to the primary member of a replica set. Applications can optionally read from secondary replicas, where data is eventually consistent by default.
How do I archive data in MongoDB?
mongodb – monthly archival of data
- Create a table with partitions based on a date field. There are typically three tables (partitions) – current (M0), previous month (M1) and previous to previous month (M2).
- Detach M2, download data and drop table. Create M2 (empty) again.
Does MongoDB lose data?
MongoDB can lose data in many startling ways Cause unknown. Recovery on corrupt database was not successful, pre transaction log. Replication between master and slave had gaps in the oplogs, causing slaves to be missing records the master had.
Is MongoDB strong consistency?
By default, MongoDB is a strongly consistent system. Once a write completes, any subsequent read will return the most recent value. Cassandra, by default, is an eventually consistent system. Once a write completes, the latest data eventually becomes available provided no subsequent changes are made.
What is MongoDB online archive?
We’re thrilled to announce that MongoDB Atlas Online Archive is now Generally Available. Online Archive allows you to seamlessly tier your data across Atlas clusters and fully managed cloud object stores, while retaining the ability to query it through a single endpoint. Reduce storage costs.
Is MongoDB good for transactional?
MongoDB is empowering the next generation of applications: post-transactional applications that rely on bigger data sets that move much faster than an RDBMS can handle.
What is MongoDB transaction?
For situations that require atomicity of reads and writes to multiple documents (in a single or multiple collections), MongoDB supports multi-document transactions. With distributed transactions, transactions can be used across multiple operations, collections, databases, documents, and shards.
How does an archive cluster work in MongoDB?
Archive Cluster Data ¶ Atlas offers a feature that moves infrequently accessed data from your Atlas cluster to a MongoDB-managed read-only Data Lake on a cloud object storage without user action. Once Atlas archives the data, you have a unified view of your Atlas and Online Archive data using a read-only Data Lake.
What is the syntax for month in MongoDB?
Returns the month of a date as a number between 1 and 12. The $month expression has the following operator expression syntax: Changed in version 3.6. The argument must be a valid expression that resolves to one of the following:
Is the$ month operator used in MongoDB aggregation?
The following aggregation uses the $month and other date operators to break down the date field: The operation returns the following result: © MongoDB, Inc 2008-present. MongoDB, Mongo, and the leaf logo are registered trademarks of MongoDB, Inc.
How does the Atlas function work in MongoDB?
Atlas runs the query specified in the archiving rule to select the documents to archive. Atlas offers this Online Archive feature only on M10 and greater clusters that run MongoDB 3.6 or later. Atlas periodically runs a query to determine the documents that match the criteria for archiving. Atlas refers to this query as a job.