Differences with MongoDB

TeselaDB is compared with MongoDB 9.0 by a suite that runs the official drivers and mongosh against both. Every observable difference is recorded; a current MongoDB feature that is missing is treated as a defect. The full list of commands and operators is in Compatibility.

Stronger guarantees

• A search sees the writes committed before it. In MongoDB search indexes can lag.
• readConcern local and available return only data confirmed by a majority.
• A unique index and _id are unique across the whole cluster, also with a shard key.
• Search scores use the statistics of the whole collection and are the same on every replica.
• The MCP server starts read-only and aggregate rejects $out and $merge.
• Strings that are not valid UTF-8 are rejected with InvalidBSON.

Extensions

• The REST API and the MCP server.
• The teselaBuckets index option and TeselaDB's own explain stages.
• The cluster parameters teselaHistoryRetention, topologyPresentation, httpOptions and mcpOptions.
• local.oplog.rs can be read with the mongos presentation too.
• Encryption at rest without the Enterprise edition.

What MongoDB does not guarantee

• A find without sort returns documents in key order, not insertion order.
• The planner may pick another index; explain and the order without sort change, never the documents returned.

Deprecated features

What MongoDB 9.0 marks as deprecated does not exist and answers as MongoDB answers what does not exist. What drivers, mongosh and the tools still send is kept: isMaster, collStats and mapReduce.