In MongoDB, the diagnostic.data collection contains diagnostic information about the MongoDB instance, such as server logs, system information, and performance statistics. This information can be useful for troubleshooting issues and optimizing performance.
The mongod.lock file is a file that is created by the mongod process to prevent multiple instances of mongod from running concurrently on the same data directory. The file contains information about the process ID (PID) of the running mongod instance, the timestamp of the lock acquisition, and other metadata.
Regarding the diagnostic.data collection and mongod.lock file, it is worth noting that they are not directly related to MongoDB indexes. However, if you are experiencing issues with index performance or indexing is not working as expected, you can use the diagnostic information in the diagnostic.data collection and server logs to help diagnose the issue.
Some specific queries that can help diagnose index performance issues are:
Use db.collection.stats() to get statistics on the collection’s indexes, such as the size and number of documents in each index.
Use db.currentOp() to get information about the currently running operations, including queries that are taking a long time to execute. You can use this information to identify slow queries and optimize them.
Use db.collection.explain() to get information about how MongoDB is executing a query, including which indexes it is using and how many documents it is scanning. You can use this information to optimize your indexes and queries.
Overall, monitoring and analyzing the diagnostic.data collection and server logs can help you identify performance issues and optimize your MongoDB instance for indexing and other operations.