lesson4

Unit 3, Lesson 4 - Performing Batch Operations

As you learned in the previous lesson, RavenDB provides a low-level API that you can use to execute not trivial tasks.

In this lesson you will learn how to use operations to update a large amount of documents answering a certain criteria.

The Need to Batch Operations

Sometimes you will need to update or delete a large amount of documents answering a certain criteria.

Using SQL it would be easy. You just need to use the UPDATE and DELETE statements.

UPDATE Products SET Price = Price * 1.1 WHERE Discontinued = false;

Anyway, this is not the case when using NoSQL databases, where set based operations are not supported.

RavenDB Approach for Batch Operations

Using RavenDB, the same queries and indexes that are used for data retrieval are used for the set based operations. The syntax defining which documents to work on is exactly the same as you'd specified for those documents to be pulled from the store.

Exercise: Increasing the PricePerUnit for non-discontinued products

In this exercise, you will learn how to increase prices of all non-discontinued products.

Step 1: Create a new project and install the latest RavenDB.Client package

Start Visual Studio and create a new Console Application Project named BatchOperationsWithRavenDB. Then, in the Package Manager Console, issue the following command:

Install-Package RavenDB.Client -Version 5.4.5

Step 2: Initialize the DocumentStore

Here we go again. let's manage the DocumentStore using our great friend DocumentStoreHolder pattern.

using System;
using Raven.Client;
using Raven.Client.Documents;

namespace BatchOperationsWithRavenDB
{
    public static class DocumentStoreHolder
    {
        private static readonly Lazy<IDocumentStore> LazyStore =
            new Lazy<IDocumentStore>(() =>
            {
                var store = new DocumentStore
                {
                    Urls = new[] { "http://localhost:8080" },
                    Database = "Northwind"
                };

                return store.Initialize();
            });

        public static IDocumentStore Store =>
            LazyStore.Value;
    }
}

Step 3: Performing a batch operation

We now have everything we need to perform a batch operation. Let's do it.

static void Main()
{
    var operation = DocumentStoreHolder.Store
        .Operations
        .Send(new PatchByQueryOperation(@"from Products as p
                                where p.Discontinued = false
                                update
                                {
                                    p.PricePerUnit = p.PricePerUnit * 1.1
                                }"));
    operation.WaitForCompletion();
}

There is a very good list of examples available on the RavenDB documentation.

Run it and check the results!

Before you go ...

You just learned how to update documents in the server without having to load it in the client side. This is an extremely powerful concept. But remember "With great powers comes great responsibility".

Great job!

Let's move onto Lesson 5.