Unused Assembly Cleanup

Article
07/16/2015

Applies To: SQL Server 2016 Preview

The AssemblyCleanup sample contains a .NET Stored Procedure that cleans-up unused assemblies in the current database by querying the metadata catalogs. Its only parameter, visible_assemblies, is used to specify whether unused visible assemblies should be dropped or not. A value of 'false' means by default only unused invisible assemblies will be dropped, otherwise all unused assemblies will be dropped. The set of unused assemblies are those assemblies that do not have any entry points defined (routines / types and aggregates) and there are no used assemblies referencing them directly or indirectly.

Prerequisites

To create and run this project the following the following software must be installed:

SQL Server or SQL Server Express. You can obtain SQL Server Express free of charge from the SQL Server Express Documentation and Samples Web site
The AdventureWorks database that is available at the SQL Server Developer Web site
.NET Framework SDK 2.0 or later or Microsoft Visual Studio 2005 or later. You can obtain .NET Framework SDK free of charge.
In addition, the following conditions must be met:
The SQL Server instance you are using must have CLR integration enabled.
In order to enable CLR integration, perform the following steps:

Enabling CLR Integration
- Execute the following Transact-SQL commands:
sp_configure 'clr enabled', 1

GO

RECONFIGURE

GO

Note

To enable CLR, you must have ALTER SETTINGS server level permission, which is implicitly held by members of the sysadmin and serveradmin fixed server roles.
The AdventureWorks database must be installed on the SQL Server instance you are using.
If you are not an administrator for the SQL Server instance you are using, you must have an administrator grant you CreateAssembly permission to complete the installation.

Building the Sample

Create and run the sample by using the following instructions:

Open a Visual Studio or .NET Framework command prompt.
If necessary, create a directory for your sample. For this example, we will use C:\MySample.
In c:\MySample, create AssemblyCleanup.vb (for the Visual Basic sample) or AssemblyCleanup.cs (for the C# sample) and copy the appropriate Visual Basic or C# sample code (below) into the file.
Compile the sample code from the command line prompt by executing one of the following, depending on your choice of language.
- Vbc /reference:C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Data.dll,C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.dll,C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Transactions.dll,C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Xml.dll /target:library AssemblyCleanup.vb
- Csc /reference:C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Data.dll /reference:C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.dll /reference:C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.XML.dll /target:library AssemblyCleanup.cs
Copy the Transact-SQL installation code into a file and save it as Install.sql in the sample directory.
If the sample is installed in a directory other then C:\MySample\, edit the file Install.sql as indicated to point to that location.
Deploy the assembly and stored procedure by executing
- sqlcmd -E -I -i install.sql
Copy Transact-SQL test command script into a file and save it as test.sql in the sample directory.
Execute the test script with the following command
- sqlcmd -E -I -i test.sql
Copy the Transact-SQL cleanup script into a file and save it as cleanup.sql in the sample directory.
Execute the script with the following command
- sqlcmd -E -I -i cleanup.sql

Sample Code

The following are the code listings for this sample.

using System;
using System.Text;
using System.Diagnostics;
using System.Data.SqlClient;
using System.Collections.Generic;
using System.Globalization;
using Microsoft.SqlServer.Server;


    /// <summary>
    /// Defines a CLR user defined function CleanupUnusedAssemblies that drops 
    /// all the invisible assemblies with no references.
    /// </summary>
    public sealed class AssemblyCleanup
    {
        private SqlTransaction transaction;

        internal class AssemblySet
        {
            private Dictionary<int, object> m_dictionary;

            /// <summary>
            /// Initialize internal structures
            /// </summary>
            /// <returns></returns>
            public AssemblySet()
            {
                m_dictionary = new Dictionary<int, object>();
            }

            /// <summary>
            /// Adds an assembly id into the current AssemblySet if it is not 
            /// already part of it.
            /// </summary>
            /// <returns></returns>
            public void Add(int assemblyId)
            {
                if (!m_dictionary.ContainsKey(assemblyId))
                {
                    m_dictionary.Add(assemblyId, null);
                }
            }

            /// <summary>
            /// Number of assembly ids stored in this instance
            /// </summary>
            /// <returns></returns>
            public int Count
            {
                get
                {
                    return m_dictionary.Count;
                }
            }

            /// <summary>
            /// Returns the comma-separated list of assembly ids contained in this instance
            /// </summary>
            /// <returns>string value that represents a comma-seperated list 
            /// of assembly ids</returns>
            public string ToCommaSeperatedList()
            {
                StringBuilder sb = new StringBuilder();

                if (m_dictionary.Count > 0)
                {
                    foreach (KeyValuePair<int, object> kv in m_dictionary)
                    {
                        sb.Append(kv.Key);
                        sb.Append(",");
                    }

                    sb.Length--; // remove the trailing comma
                }

                return sb.ToString();
            }
        }

        /// <summary>
        /// Initializes an instance of AssemblyCleanup with a SqlTransaction
        /// </summary>
        /// <returns></returns>
        private AssemblyCleanup(SqlTransaction transaction)
        {
            this.transaction = transaction;
        }

        /// <summary>
        /// Helper function that creates a SqlCommand object as part of the current 
        /// transaction
        /// </summary>
        /// <returns></returns>
        private SqlCommand CreateCommandInTransaction()
        {
            SqlCommand cmd = this.transaction.Connection.CreateCommand();

            cmd.Transaction = this.transaction;

            return cmd;
        }

        /// <summary>
        /// Helper function that constructs an AssemblySet instance using the 
        /// first column of the resultset resulting from the query that was passed in.
        /// </summary>
        /// <param name="query"></param>
        /// <returns></returns>
        private AssemblySet GetAssemblySetFromQuery(string query)
        {
            SqlCommand cmd = CreateCommandInTransaction();

            AssemblySet set = new AssemblySet();

            cmd.CommandText = query;
            using (SqlDataReader rd = cmd.ExecuteReader())
            {
                while (rd.Read())
                {
                    set.Add(rd.GetInt32(0));
                }
            }

            return set;
        }

        /// <summary>
        /// Constructs a DROP ASSEMBLY T-SQL statement using the AssemblySet 
        /// passed in as a parameter.
        /// </summary>
        /// <param name="set"></param>
        /// <returns></returns>
        private void DropAssemblies(AssemblySet unusedAssemblySet)
        {
            if (unusedAssemblySet.Count > 0)
            {
                StringBuilder assemblyNamesToDrop = new StringBuilder();

                // Gather the list of assembly names we will drop later
                SqlCommand cmd = CreateCommandInTransaction();

                cmd.CommandText = String.Format(CultureInfo.InvariantCulture,
                    "SELECT name FROM sys.assemblies WHERE assembly_id IN ({0});",
                    unusedAssemblySet.ToCommaSeperatedList());
                using (SqlDataReader rd = cmd.ExecuteReader())
                {
                    while (rd.Read())
                    {
                        assemblyNamesToDrop.Append("[");
                        assemblyNamesToDrop.Append(rd.GetString(0));
                        assemblyNamesToDrop.Append("],");
                    }
                }

                // Remove trailing comma
                assemblyNamesToDrop.Length--;

                // Drop all assemblies at the same time
                cmd.CommandText = String.Format(CultureInfo.InvariantCulture,
                    "DROP ASSEMBLY {0}", assemblyNamesToDrop.ToString());
                cmd.ExecuteNonQuery();
            }
        }

        /// <summary>
        /// Serves as the stored procedure entry point and drives the process 
        /// of expanding the "assemblies in use" set, negating it, and 
        /// dropping the results
        /// </summary>
        /// <param name="visibleAssemblies">If set to true, will also drop 
        /// unused visible assemblies. Otherwise, will only drop unused invisible 
        /// assemblies.</param>
        /// <returns></returns>
        [Microsoft.SqlServer.Server.SqlProcedure()]
        public static void CleanupUnusedAssemblies(bool visibleAssemblies)
        {
            bool succeeded = false;
            SqlConnection conn;
            SqlTransaction transaction;
            string sqlStatement;
            AssemblySet assembliesToDrop;
            AssemblyCleanup assemblyCleanup;

            conn = new SqlConnection("context connection=true");
            conn.Open();
            transaction = conn.BeginTransaction();

            try
            {
                // Create a set of assemblies in use by looking at 
                // the metadata of the current database
                sqlStatement =
                    "DECLARE @UsedAssembly TABLE (AssemblyID int NOT NULL); " +
                    "DECLARE @RowCount int; " +
                    "INSERT INTO @UsedAssembly " +
                    "SELECT DISTINCT([assembly_id]) " +
                    "FROM sys.assembly_modules " +
                    "UNION " +
                    "SELECT [assembly_id] " +
                    "FROM sys.assembly_types; " +
                    "SET @RowCount = @@ROWCOUNT; " +
                    "WHILE @RowCount > 0 " +
                    "BEGIN " +
                    "INSERT INTO @UsedAssembly " +
                    "SELECT [referenced_assembly_id] " +
                    "FROM sys.assembly_references ar " +
                    "INNER JOIN @UsedAssembly ua " +
                    "ON ar.[assembly_id] = ua.AssemblyID " +
                    "WHERE NOT EXISTS (SELECT * FROM @UsedAssembly WHERE AssemblyID = [referenced_assembly_id]) " +
                    "SET @RowCount = @@ROWCOUNT; " +
                    "END;";

                if (visibleAssemblies)
                {
                    sqlStatement +=
                        "SELECT assembly_id " +
                        "FROM sys.assemblies " +
                        "WHERE assembly_id NOT IN (SELECT AssemblyID FROM @UsedAssembly);";
                }
                else
                {
                    sqlStatement +=
                        "SELECT assembly_id " +
                        "FROM sys.assemblies " +
                        "WHERE assembly_id NOT IN (SELECT AssemblyID FROM @UsedAssembly) " +
                        "    AND is_visible = 0;";
                }

                // This marks the beginning of the transaction
                assemblyCleanup = new AssemblyCleanup(transaction);

                // Assemblies that are currently in use
                assembliesToDrop
                    = assemblyCleanup.GetAssemblySetFromQuery(sqlStatement);

                assemblyCleanup.DropAssemblies(assembliesToDrop);

                // Mark as succeeded
                succeeded = true;
            }
            finally
            {
                // We must guarantee that we explicitly call either Commit() 
                // or Rollback() before we return.
                if (succeeded)
                {
                    transaction.Commit();
                }
                else
                {
                    transaction.Rollback();
                }
                conn.Dispose();
            }
        }
    }

Visual Basic

Imports Microsoft.SqlServer.Server
Imports Microsoft.VisualBasic
Imports System
Imports System.Collections
Imports System.Collections.Generic
Imports System.Data
Imports System.Data.SqlClient
Imports System.Diagnostics
Imports System.Globalization
Imports System.Text
Imports System.Transactions
Public NotInheritable Class AssemblyCleanup
    Private transaction As SqlTransaction

    Friend Class AssemblySet
        Private m_dictionary As Dictionary(Of Integer, Object)

        ''' <summary>
        ''' Initialize internal structures
        ''' </summary>
        ''' <returns></returns>
        Public Sub New()
            m_dictionary = New Dictionary(Of Integer, Object)
        End Sub

        ''' <summary>
        ''' Adds an assembly id into the current AssemblySet if it is not already part of it.
        ''' </summary>
        ''' <returns></returns>
        Public Sub Add(ByVal assemblyId As Integer)
            If Not m_dictionary.ContainsKey(assemblyId) Then
                m_dictionary.Add(assemblyId, Nothing)
            End If
        End Sub

        ''' <summary>
        ''' Number of assembly ids stored in this instance
        ''' </summary>
        ''' <returns></returns>
        Public ReadOnly Property Count() As Integer
            Get
                Return m_dictionary.Count
            End Get
        End Property

        ''' <summary>
        ''' Returns the comma-separated list of assembly ids contained in this instance
        ''' </summary>
        ''' <returns>string value that represents a comma-seperated list of assembly ids</returns>
        Public Function ToCommaSeperatedList() As String
            Dim sb As New StringBuilder()

            If m_dictionary.Count > 0 Then
                For Each kv As KeyValuePair(Of Integer, Object) In m_dictionary
                    If (True) Then
                        sb.Append(kv.Key)
                        sb.Append(",")
                    End If
                Next

                sb.Length -= 1 ' remove the trailing comma
            End If

            Return sb.ToString()

        End Function
    End Class

    ''' <summary>
    ''' Initializes an instance of AssemblyCleanup with a SqlTransaction
    ''' </summary>
    ''' <returns></returns>
    Private Sub New(ByVal trans As SqlTransaction)
        Me.transaction = trans
    End Sub

    ''' <summary>
    ''' Helper function that creates a SqlCommand object as part of the 
    ''' current transaction
    ''' </summary>
    ''' <returns></returns>
    Private Function CreateCommandInTransaction() As SqlCommand
        Dim cmd As SqlCommand = transaction.Connection.CreateCommand()

        cmd.Transaction = Me.transaction

        Return cmd
    End Function

    ''' <summary>
    ''' Helper function that constructs an AssemblySet instance using the 
    ''' first column of the resultset resulting from the query that was passed in.
    ''' </summary>
    ''' <param name="query"></param>
    ''' <returns></returns>
    Private Function GetAssemblySetFromQuery(ByVal query As String) As AssemblySet
        Dim cmd As SqlCommand = CreateCommandInTransaction()
        Dim [set] As New AssemblySet()

        cmd.CommandText = query
        Dim rd As SqlDataReader = cmd.ExecuteReader()
        Try
            While rd.Read()
                [set].Add(rd.GetInt32(0))
            End While
        Finally
            rd.Dispose()
        End Try

        Return [set]
    End Function

    ''' <summary>
    ''' Constructs a DROP ASSEMBLY T-SQL statement using the AssemblySet 
    ''' passed in as a parameter.
    ''' </summary>
    ''' <param name="set"></param>
    ''' <returns></returns>
    Private Sub DropAssemblies(ByVal unusedAssemblySet As AssemblySet)
        If unusedAssemblySet.Count > 0 Then
            Dim assemblyNamesToDrop As New StringBuilder()

            ' Gather the list of assembly names we will drop later
            Dim cmd As SqlCommand = CreateCommandInTransaction()


            cmd.CommandText = String.Format(CultureInfo.InvariantCulture, _
                "SELECT name FROM sys.assemblies WHERE assembly_id IN ({0});", _
                unusedAssemblySet.ToCommaSeperatedList())
            Dim rd As SqlDataReader = cmd.ExecuteReader()
            Try
                While rd.Read()
                    assemblyNamesToDrop.Append("[")
                    assemblyNamesToDrop.Append(rd.GetString(0))
                    assemblyNamesToDrop.Append("],")
                End While
            Finally
                rd.Dispose()
            End Try

            ' Remove trailing comma
            assemblyNamesToDrop.Length -= 1

            ' Drop all assemblies at the same time
            cmd.CommandText = String.Format(CultureInfo.InvariantCulture, _
                "DROP ASSEMBLY {0}", assemblyNamesToDrop.ToString())
            cmd.ExecuteNonQuery()
        End If
    End Sub

    ''' <summary>
    ''' Serves as the stored procedure entry point and drives the process of 
    ''' expanding the "assemblies in use" set, negating it, and dropping 
    ''' the results.
    ''' </summary>
    ''' <param name="visibleAssemblies">If set to true, will also drop unused 
    ''' visible assemblies. Otherwise, will only drop unused invisible assemblies.</param>
    ''' <returns></returns>
    <Microsoft.SqlServer.Server.SqlProcedure()> _
    Public Shared Sub CleanupUnusedAssemblies(ByVal visibleAssemblies As Boolean)

        Dim succeeded As Boolean = False
        Dim conn As SqlConnection
        Dim transaction As SqlTransaction
        Dim sqlStatement As String
        Dim assembliesToDrop As AssemblySet
        Dim assemblyCleanup As AssemblyCleanup

        conn = New SqlConnection("context connection=true")
        conn.Open()
        transaction = conn.BeginTransaction()

        Try
            ' Create a set of assemblies in use by looking at 
            ' the metadata of the current database
            sqlStatement = "DECLARE @UsedAssembly TABLE (AssemblyID int NOT NULL); " & _
                "DECLARE @RowCount int; " & _
                "INSERT INTO @UsedAssembly " & _
                "SELECT DISTINCT([assembly_id]) " & _
                "FROM sys.assembly_modules " & _
                "UNION " & _
                "SELECT [assembly_id] " & _
                "FROM sys.assembly_types; " & _
                "SET @RowCount = @@ROWCOUNT; " & _
                "WHILE @RowCount > 0 " & _
                "BEGIN " & _
                "INSERT INTO @UsedAssembly " & _
                "SELECT [referenced_assembly_id] " & _
                "FROM sys.assembly_references ar " & _
                "INNER JOIN @UsedAssembly ua " & _
                "ON ar.[assembly_id] = ua.AssemblyID " & _
                "WHERE NOT EXISTS (SELECT * FROM @UsedAssembly WHERE AssemblyID = [referenced_assembly_id]) " & _
                "SET @RowCount = @@ROWCOUNT; " & _
                "END;"

            If visibleAssemblies Then
                sqlStatement += "SELECT assembly_id " & _
                    "FROM sys.assemblies " & _
                    "WHERE assembly_id NOT IN (SELECT AssemblyID FROM @UsedAssembly);"
            Else
                sqlStatement += "SELECT assembly_id " & _
                    "FROM sys.assemblies " & _
                    "WHERE assembly_id NOT IN (SELECT AssemblyID FROM @UsedAssembly) " & _
                    "    AND is_visible = 0;"
            End If

            ' This marks the beginning of the transaction
            assemblyCleanup = New AssemblyCleanup(transaction)

            ' Assemblies that are currently in use
            assembliesToDrop _
                = assemblyCleanup.GetAssemblySetFromQuery(sqlStatement)

            assemblyCleanup.DropAssemblies(assembliesToDrop)

            ' Mark as succeeded
            succeeded = True
        Finally
            ' We must guarantee that we explicitly call either Commit() 
            ' or Rollback() before we return.
            If succeeded Then
                transaction.Commit()
            Else
                transaction.Rollback()
            End If
            conn.Dispose()
        End Try
    End Sub
End Class

This is the Transact-SQL installation script (Install.sql), which deploys the assembly and creates the stored procedure in the database.

USE AdventureWorks;
GO
IF EXISTS (SELECT * FROM sys.objects WHERE name = N'CleanupUnusedAssemblies')
DROP PROCEDURE CleanupUnusedAssemblies;
GO

IF EXISTS (SELECT * FROM sys.assemblies WHERE name = N'AssemblyCleanupUtils') 
DROP ASSEMBLY AssemblyCleanupUtils;
GO
DECLARE @SamplesPath nvarchar(1024)

-- You may need to modify the value of the this variable if you have installed the sample someplace other than the default location.
Set @SamplesPath = 'C:\MySample\'

CREATE ASSEMBLY AssemblyCleanupUtils 
FROM @SamplesPath + 'AssemblyCleanup.dll' 
WITH permission_set = Safe;
GO

CREATE PROCEDURE CleanupUnusedAssemblies (
@visible_assemblies bit
) AS
EXTERNAL NAME [AssemblyCleanupUtils].[AssemblyCleanup].CleanupUnusedAssemblies;
GO

This is test.sql, which tests the sample by executing the stored procedure.

USE AdventureWorks;
GO

PRINT 'Before cleanup...'
SELECT [name] FROM sys.assemblies;
GO

-- pass in false, which means the cleanup will only include invisible assemblies
EXEC dbo.CleanupUnusedAssemblies false;
GO

PRINT 'After cleanup'
SELECT [name] FROM sys.assemblies;

The following Transact-SQL removes the assembly and stored procedure from the database.

USE AdventureWorks;
GO

IF EXISTS (SELECT * FROM sys.objects WHERE name = N'CleanupUnusedAssemblies')
DROP PROCEDURE CleanupUnusedAssemblies;
GO

IF EXISTS (SELECT * FROM sys.assemblies WHERE name = N'AssemblyCleanupUtils') 
DROP ASSEMBLY AssemblyCleanupUtils;
GO

Unused Assembly Cleanup

Prerequisites

Enabling CLR Integration

Building the Sample

Create and run the sample by using the following instructions:

Sample Code

See Also

Additional resources