The server will return an error in 5.1.0 whenever it receives an OP_QUERY find operation or an OP_GET_MORE. It will also return an error for OP_QUERY commands other than hello/isMaster.

The server will not service OP_INSERT, OP_DELETE, OP_UPDATE, or OP_KILL_CURSORS messages. All it will do in 5.1.0 upon receipt of these messages is close the connection.

As part of PM-912, starting with 5.1.0, all of the OP_QUERY-specific operators listed here will be removed (except for $natural, which is not affected): https://docs.mongodb.com/manual/reference/operator/query-modifier/. To provide explicit examples, we are removing support for $explain and $query, since these only make sense in the context of --readMode "legacy":

https://docs.mongodb.com/manual/reference/operator/meta/explain/
https://docs.mongodb.com/manual/reference/operator/meta/query/

Also we're removing the following mongo shell command-line parameters

• useLegacyWriteOps
• writeMode
• readMode
• rpcProtocols

The mongo shell will no longer support the OP_QUERY RPC protocol, but rather will always use OP_MSG (except for running an OP_QUERY isMaster as part of the connection handshake). For this reason, the mongo shell will no longer successfully connect to servers older than 3.6.

Summary

Remove support for OP_QUERY, OP_GET_MORE, OP_KILL_CURSORS, OP_DELETE, OP_UPDATE, OP_INSERT, and the getLastError command.

Motivation

These legacy wire protocol formats have long been out of use, as modern drivers favor the OP_MSG protocol. They are being deprecated by PM-911. There is plenty of server code that can be dramatically simplified by removing support for these old wire protocol op codes.

Documentation

[Scope Document]