How to Optimize SQL Server Memory Usage When Using SqlDependency?

Optimizing SQL Server Memory Usage with SqlDependency

The Challenge:

Using SQL Server's SqlDependency class often results in a memory leak. Unused SqlDependency objects accumulate, leading to high resource consumption and potential memory exhaustion, especially noticeable in SQL Server Express. Efficiently removing these obsolete dependencies is key to maintaining optimal performance.

The Solution:

Simply stopping dependencies with SqlDependency.Stop() isn't sufficient; conversation groups and endpoints remain in the database. To address this, run the following SQL script to clean up these lingering resources:

<code class="language-sql">DECLARE @ConvHandle uniqueidentifier
DECLARE Conv CURSOR FOR
SELECT CEP.conversation_handle FROM sys.conversation_endpoints CEP
WHERE CEP.state = 'DI' or CEP.state = 'CD'
OPEN Conv;
FETCH NEXT FROM Conv INTO @ConvHandle;
WHILE (@@FETCH_STATUS = 0) BEGIN
    END CONVERSATION @ConvHandle WITH CLEANUP;
    FETCH NEXT FROM Conv INTO @ConvHandle;
END
CLOSE Conv;
DEALLOCATE Conv;</code>

A Superior Alternative: SqlDependencyEx

The standard SqlDependency class has limitations, notably its inability to reliably track all table modifications during re-subscription. A more robust alternative is SqlDependencyEx, an open-source solution utilizing database triggers and native Service Broker notifications. This provides more reliable change notifications and avoids the memory problems inherent in the Microsoft implementation.

Here's an example using SqlDependencyEx:

<code class="language-csharp">int changesReceived = 0;
using (SqlDependencyEx sqlDependency = new SqlDependencyEx(
          TEST_CONNECTION_STRING, TEST_DATABASE_NAME, TEST_TABLE_NAME)) 
{
    sqlDependency.TableChanged += (o, e) => changesReceived++;
    sqlDependency.Start();

    // Simulate table changes.
    MakeTableInsertDeleteChanges(changesCount);

    // Allow time for change detection.
    Thread.Sleep(1000);
}

Assert.AreEqual(changesCount, changesReceived);</code>

This approach ensures timely notification of data changes and effectively mitigates the memory issues associated with the built-in SqlDependency class.

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