MongoDB - Execute a command conditionally - mongodb

Question

I need to execute a command that is part of my migration scripts (mongock java library) conditionally based on Mongo version
In case Mongo version is lower then 4.2 I need to execute this command. For Mongo 4.2 and higher it should not be executed.
db.getSiblingDB('admin').runCommand( { setParameter: 1, failIndexKeyTooLong: false } )
Is there a way how to do it?
Thank you,
Lukas

Answer 1

don't know if you already found a solution for this.
The idea is to figure out the Mongo's version inside the changeSet and then perform the required actions.
I will assume you are using the last Mongock's release for version 3.x.x, which is 3.3.2 or 4.0.x.alpha, so you should use MongockTemplate, instead of MongoTemplate. Don't worry, it's just a wrapper/decorator, you won't miss anything from the original API.
So you can do something like this:
#ChangeSet(id = "changeset-1", order = "001", author = "mongock")
public void changeSet(MongockTemplate mongockTemplate, ClientRepository clientRepository) {
String version = mongockTemplate.executeCommand(new Document("buildinfo", new BsonString("")))
.get("version")
.toString();
if(getNumericalVersion(version) < 42) {
//do your actions
} else {
//do you other actions
}
}
NOTE 1: We don't recommend using executeCommand. In this case, for taking the version it's fine, but in general we recommend not using it, specially for writes.
NOTE 2: Currently we are working on version 4, which will allow to scan multiple packages and even isolated ChangeLog classes. So another approach would be to take the version in the bean creation and inject the change or not depending on the MongoDB's version