Migrating schema and data in Azure Table Storage

Recently I faced a problem, when I had to change and adjust schema in tables stored in Azure Table Storage. The issue there was to actually automate changes so I don't have to perform them manually on each environment. This was the reason why I created a simple library called AzureTableStorageMigratorwhich helps in such tasks and eases the whole process.

The basics

The base idea was to actually create two things:

  • a simple fluent API, which will take care of chaining all tasks
  • a table which will hold all migration metadata

Current version(1.0) gives you following possibilities:

  • void Insert<T>(string tableName, T entity, bool createIfNotExists = false)
  • void DeleteTable(string tableName)
  • void CreateTable(string tableName)
  • void RenameTable<T>(string originTable, string destinationTable)
  • void Delete<T>(string tableName, T entity)
  • void Delete(string tableName, string partitionKey)
  • void Delete(string tableName, string partitionKey, string rowKey)
  • void Clear(string tableName)

and when you take a look at the example of usage:

var migrator = new Migrator();
migrator.CreateMigration(_ =>
  _.Insert("table1", new DummyEntity { PartitionKey = "pk", RowKey = DateTime.UtcNow.Ticks.ToString(), Name = "foo"});
  _.Insert("table1", new DummyEntity { PartitionKey = "pk", RowKey = DateTime.UtcNow.Ticks.ToString(), Name = "foo2"});
  _.Insert("table2", new DummyEntity { PartitionKey = "pk", RowKey = DateTime.UtcNow.Ticks.ToString(), Name = "foo"});
}, 1, "1.1", "My first migration!");

you'll see, that's pretty straightforward and self-describing. 

The way how it works is very simple - each CreateMigration() method is described using 3 different values - its id, version number and description. Each time this method is called, it'll add a new record to the versionData table to make sure, that metadata is saved and the same migration won't be run twice.

Why should I use it?

In fact it's not a matter of what you "should" do but rather what is "good" for your project. Versioning is generally a good idea, especially if you follow CI/CD pattern, where the goal is to deploy and rollback with ease. If you perform migrations by hand, you'll eventually face the situation, where rollback is either very time-consuming or almost impossible. 

It's good to remember that making your database a part of your repository(of course in terms of storing schema, not data) is considered a good practice and is one of the main parts of many modern projects.

What's next?

I published ATSM because I couldn't find a tool similar to it, which would help me version tables in Table Storage easily. For sure some new features will be added in the future, however if you find this project interesting, feel free to post an issue or a request - I'll be more than happy to discuss it.