SQL Azure Federation Splitting Design and Querying

Question

I have a few questions regarding Microsoft SQL Azure Federations:

1) Can I created a federated DB on an active Database or do I need to deploy federations ahead of time?

2) Do I need to make any changes to the SQL queries to comply with how I query federations, or I can continue to use my regular queries as I was working against one SQL Server Database?

3) When I split my database and after some time I see that one of the shards is very busy and almost full, how I tackle this problem using federations? - Do I need to split only that single federated table that is 90% full, or I need to recreate the splitting strategy by using a a less broader range. The problem is that one specific user can be very active, so what strategy I use to making sure that I won't need to re-create the federated strategy due to one very active federated table / user?

4) When I have different tables that I want to split with different primary keys, how the sharding will work then. for example:

From what I understand:

[Blogs]

blog_id

info

[Blog_Posts]

id

blog_id

post_content

So if I decide to shard based on the blog_id from 0-1000, 1-2001 I will have two federated tables. But how much more federated tables I have if I add more tables that have different keys other than blog_id, will I have more federated tables?

Thanks

Answer 1

Please be more precise and concrete and ask one question at a time. You have better chance for getting an answer to all of the questions when asked separately. Now let me try covering some of your questions.

1) Can I created a federated DB on an active Database or do I need to deploy federations ahead of time?

You can certainly create a Federation(s) within an existing DB. There is no limitation to creating Federations in just a new/empty DB. However, creating a federation in an Active DB will do nothing for you. You have to realize that Federations are separate DBs. A Federation (or Federation member) knows nothing about the Federations Root DB (the DB where you created the federation). So you have to think on migrating schema/data from the Active DB (or the Federations Root) once you create your federation.

2) Do I need to make any changes to the SQL queries to comply with how I query federations, or I can continue to use my regular queries as I was working against one SQL Server Database?

Most probably YES. Windows Azure SQL Database Federations is a Scale-Out mechanism for the DB tier. This means, that like any Web Application needs a "special" design to work in a farm-like environment (i.e. scale-out environment like Windows Azure), a DataBase will also need a "special" design to work in a scale-out environment. There is no magic-wand with SQL Azure Federations that will make your code work. You have to design it to Work.

3) When I split my database and after some time I see that one of the shards is very busy and almost full, how I tackle this problem using federations? - Do I need to split only that single federated table that is 90% full, or I need to recreate the splitting strategy by using a a less broader range. The problem is that one specific user can be very active, so what strategy I use to making sure that I won't need to re-create the federated strategy due to one very active federated table / user?

This is all about partitioning strategy. You have to very carefully design your federation key and how you partition your data across different shards. You can always SPLIT any federation, as long as you keep the Atomic Units in single shard.

4) When I have different tables that I want to split with different primary keys, how the sharding will work then.

If you want to split different tables on different keys, than you will have different federations, each one with its own federation key and own tables.

A good video worth watching if you are up for SQL Federations: http://channel9.msdn.com/Events/TechEd/NorthAmerica/2012/DBI408