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How we can remove millions of entities from a Windows Azure Table (part 2)

In one of my latest post I tacked about how we can remove a lot of entities from Windows Azure – deleting the table.
This solution works but we will have to face up with an odd problem. When we are deleting a table, we only mark it for deletion, our client will not be able to access the table and in background Windows Azure will start deleting the table. If we have a table with millions of entities will face up with a big problem. Until Windows Azure will finish deletion of the table will not be able to create a new table with the same time.
This can be a blocker. We don’t want to wait 4 hours, until our table is deleted to be able to recreate another one.
And here is a big BUT. We can be smart and use ListTables. Basically we can create another table that have the name something like [MyTableName]+[Guid] and using ListTable method to retrieve the name of our table only using [MyTableName].
Using this solution, we can add mark our old table for delegation and create a new table with a similar name where we can store our entities. In this way we will be able to remove items from a table in only a few seconds.  Even if this “virtual” clean it works great and can speed up our applications.
The following code can be used to delete a table:
CloudTableClient tableStorage = new CloudTableClient([tableUri],[credential]);
string tableName = [MyTableName];
tableName = tableStorage.ListTables(tableName).FirstOrDefault();
if (tableName != null)
{
  tableStorage.DeleteTableIfExist(tableName);
}
The following code can be used to retrieve the name of our table and recreate a new table of don’t exist:
string tableName = tableStorage.ListTables([MyTableName]).FirstOrDefault();
if (tableName == null)
{
  tableName = [MyTableName] + Guid.NewGuid();
  tableStorage.CreateTableIfNotExist(tableName);
}

The only downside of this solution is that there are some seconds when we will not have a table where clients can access it. If we can leave with this solution and we can manage this problem on the client side than we can use it without any kind of problem.

Comments

  1. The question is: why/when would you need to do something like this is a real application? :)
    (sure, for testing/debugging scenarios it might be useful, but other than that..)

    ReplyDelete
    Replies
    1. There are times when you need to clean a table very fast. For example a table that store the assignment between updates and system where this update is available.

      Delete

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