jLinq in MongoDB (Oh snap!!)

My new project CSMongo, a Mongo driver for .NET, is now online! Check it out!

Yeah, you read that right – jLinq in MongoDB!

Lately I’ve been working on a Mongo database driver and I got to thinking — Since I can use Javascript with MongoDB then I wonder if I could use jLinq to write queries? As it turns out the answer is yes!

… and if you don’t know what jLinq is… – jLinq is a javascript query language, similar to the LINQ project created by Microsoft, for JSON data which was designed to run within web pages using Javascript

Getting Started

I’m not really sure how you can get a Javascript library to load directly into MongoDB but for now I was simply copying and pasting the existing jLinq packed library into the command line and allowing it to evaluate the script — and that is it! You can use jLinq right away!

You should be aware though that you can’t just evaluate results directly. You actually need to call the toArray() function on each of them to see the results. So for example, your query would look something like…

jLinq.from(db.users.find().toArray()).startsWith("name", "h").select();

You don’t need to actually do anything with the results since they are automatically displayed on the screen for you.

So far everything works. I could do standard queries, use the OR operator, reorder records, join different databases, perform comparisons against sub-properties — really everything I’ve tried has worked just the way I’d expect it to!

Granted, database and collection names are going to be different, here are some interesting queries you can try with your database.

//Selects records where the name starts with a, b or c (case-insensitive)
jLinq.from(db.users.find().toArray())
    .startsWith("name", "a")
    .or("b")
    .or("c")
    .select();

//selects users older than 50 and are administrators then orders them by their names
jLinq.from(db.users.find().toArray())
    .greater("age", 50)
    .is("admin")
    .orderBy("name")
    .select();

//performs a join against another database to get locations
//and then queries the location to find users that live in 'texas'
//and then selects only the name of the person and location
jLinq.from(db.users.find().toArray())
    .join(db.locations.find().toArray(), "location", "locationId", "id")
    .equals("location.name", "texas")
    .select(function(rec) {
        return {
            person: rec.name,
            location: rec.location.name
        };
    });

More On jLinq

Unfortunately, it isn’t possible to go over all of the cool stuff you can do with jLinq – but here are some screencasts and blog posts that you can read that might help you get started.

jLinq Project Page
Screencast 1 – Getting Started
Screencast 2 – Extending jLinq (Custom commands)
Screencast 3 – Modifying Live Data In A Query (Joins, Assignment)
Screencast 4 – jLinq 2.2.1 (Updates)

Anyways, for now I’m not sure how to integrate jLinq into Mongo queries but keep an eye for future blog posts as I find out more.

Double Whammy – jLinq Release And Screencast!

Now that you’re all excited time for some disappointment – it is just a minor update to fix a few bugs and to add one new feature.

But instead of just blogging about it I’ve also done a new screencast to talk about the updates and new feature in this release.

• Dynamic Queries (using OR) – Before, if you used “OR” at the start of a query then you’d get an exception. jLinq would try and tag “||” at the start of your query which would cause the whole thing to collapse. Now, jLinq correctly handles this and prevents the error. In turn, writing dynamic queries just got a whole lot easier!.
• Range Comparisons With Dates – Version 2.2.0 introduced smarter comparisons by evaluating the types of values being passed in instead of expecting only one type. However, in the change, the range comparisons like greater, less, between, etc, would all incorrectly evaluate Dates as strings… bummer.
• Bitwise Flag Comparisons – jLinq 2.2.1 introduces a new query method called has which performs bitwise flag comparisons on records. It even works with regular ol’ numbers by converting them before performing the comparisons.

Anyways, go check out he new screen cast now and tell me what you think!

Bonus: CamStudio Icon

Last night while I was setting up CamStudio for this screencast I was looking at their UGLY icon they use for their program — I just couldn’t stand it being in my beautiful RocketDock – so I designed a new one for them. If you’re looking for an improved logo then you can download the PNG for the CamStudio icon.

jLinq Screencast #3 – Modifying Records During A Query

Sometimes when you get your records they aren’t exactly what you we’re needing, or sometimes some of the fields need to be formatted before they can be queried against. Fortunately, jLinq comes with that functionality built into it.

This screencast goes over several of the methods you have available to you that allow records to be formatted before they are selected.

• each(delegate(record)): Performs a loop through each of the values in the array. This code can be used to modify records, create new properties or anything you need it to do.
• attach(alias, delegate(record)): Performs the method passed in on each of the records in the array and attaches the result to the record using the alias provided.
• join(records, alias, foreignKey, primaryKey): Joins two arrays together using the alias and the keys to match the values. Joins tend to be slow when using large arrays, so use caution.

If you have any recommendations or requests for the next screencast, please let me know and I’ll see what I can do.

Side note: Never improvise on a screen cast – nothing like having to redo a screen cast twice because you say something that isn’t true and then realize it while recording. 🙂