shell-extensions

MongoDB Shell Extensions

The script mongodb-shell-extensions.js adds some handy utilities to the mongo shell.

Quick intro

Here's a simple example that condenses the utilities:

db.players.set1("5e07ce013dca4d04ea3f6552", {score:Double(5)})

This statement will do this:

db.players.update({_id:"5e07ce013dca4d04ea3f6552"}, {$set:{score:5}})

The function set1 will force you to specify the type of numbers. If you just write score:5, the statement will fail because of number type-safety.

Besides, by adding more query expansions, you could easily be able to execute a statement like this too:

db.players.set1("[email protected]", {score:Double(5)})

Below, you will find more details about how this works.

Installation

Just load the script when opening your mongo shell. You have different options:

1. Use the mongo command argument:

mongo mongodb-shell-extensions.js --shell

2. Load it from inside the shell:

load("mongodb-shell-extensions.js")

3. Add that load("mongodb-shell-extensions.js"); statement to your ~/.mongorc file so mongodb-shell-extensions.js is automatically loaded every time you start a mongo shell.

Usage

You have these new functions:

db.col.find1(q) // similar to: db.col.findOne(q)
db.col.findN(q) // similar to: db.col.find(q).pretty()
db.col.set1(q, u) // similar to: db.col.update(q, {$set: u})
db.col.setN(q, u) // similar to: db.col.update(q, {$set: u}, false, true)
db.col.safeInsert(o) // similar to: db.col.insert(o)

Those new functions have 2 peculiarities:

1. The updates u and the inserted object o are checked so that numbers are specified using explicit types like Int(1), Long(23) or Double(7). More on this in Number type-safety.
2. The query q is expanded using the function MongoUtil.expandQuery. More on this in Query expansions.

Number type-safety

The numbers in the updates u and the inserted object o must be given with explicit type, even for double values. It is mandatory to use Int, Long or Double. Those are shorter aliases for NumberInt and NumberLong (NumberDouble doesn't exist so use Double).

Examples:

db.col.safeInsert({count:Int(3), score:Double(7)})
db.col.setN({count:3}, {score:Double(7)})

Note that the query doesn't need explicit type.

Query expansions

The query q of the functions indicated before are expanded when some known object types or patterns are found. For now, they just detect that q is an ObjectId or a string that looks like an ObjectId:

db.col.set("5e07ce013dca4d04ea3f6552", {text:"hello"})

That statement is equivalent to (notice the ObjectId and the $set):

db.col.update({_id: ObjectId("5e07ce013dca4d04ea3f6552")}, {$set:{text:"hello"}})

Configuring query expansions

You may override the query expansions or add more of your own. After loading the mongodb-shell-extensions.js, modify the MongoUtil.expandQuery function.

Here's an example where we want to expand a query that looks like an email to {email: query} . This code could be in the ~/.mongorc.js file.

load("mongodb-shell-extensions.js");

// Save the original expandQuery function
const originalExpandQuery = MongoUtil.expandQuery;

// Replace expandQuery with another implementation
MongoUtil.expandQuery = function(query) {

	const emailRegex = /^[\w.\-]+@[\w.\-]+$/; // simplified regex
	if (emailRegex.test(query)) {
		return {email: query};
	}

	// Here we want to fall back to the original expansions but
	// we could `return query` to use the email expansion only.
	return originalExpandQuery(query);
};