CLR 사용자 정의 집계 함수 호출

  • 아티클

Transact-SQL SELECT 문에서 시스템 집계 함수에 적용되는 모든 규칙을 따르는 CLR(공용 언어 런타임) 사용자 정의 집계를 호출할 수 있습니다.

다음 추가 규칙이 적용됩니다.

  • 현재 사용자에게 사용자 정의 집계에 대한 EXECUTE 권한이 있어야 합니다.

  • schema_name.udagg_name 형식의 두 부분으로 구성된 이름을 사용하여 사용자 정의 집계를 호출해야 합니다.

  • 사용자 정의 집계의 인수 유형은 CREATE AGGREGATE 문에 정의된 집계의 input_type과 일치하거나 암시적으로 해당 유형으로 변환될 수 있어야 합니다.

  • 사용자 정의 집계의 반환 형식은 CREATE AGGREGATE 문의 return_type과 일치해야 합니다.

예 1

테이블의 열에서 가져온 문자열 값 집합을 연결하는 사용자 정의 집계 함수의 예는 다음과 같습니다.

[C#]

using System;
using System.Data;
using Microsoft.SqlServer.Server;
using System.Data.SqlTypes;
using System.IO;
using System.Text;

[Serializable]
[SqlUserDefinedAggregate(
    Format.UserDefined, //use clr serialization to serialize the intermediate result
    IsInvariantToNulls = true, //optimizer property
    IsInvariantToDuplicates = false, //optimizer property
    IsInvariantToOrder = false, //optimizer property
    MaxByteSize = 8000) //maximum size in bytes of persisted value
]
public class Concatenate : IBinarySerialize
{
    /// <summary>
    /// The variable that holds the intermediate result of the concatenation
    /// </summary>
    private StringBuilder intermediateResult;

    /// <summary>
    /// Initialize the internal data structures
    /// </summary>
    public void Init()
    {
        this.intermediateResult = new StringBuilder();
    }

    /// <summary>
    /// Accumulate the next value, not if the value is null
    /// </summary>
    /// <param name="value"></param>
    public void Accumulate(SqlString value)
    {
        if (value.IsNull)
        {
            return;
        }

        this.intermediateResult.Append(value.Value).Append(',');
    }

    /// <summary>
    /// Merge the partially computed aggregate with this aggregate.
    /// </summary>
    /// <param name="other"></param>
    public void Merge(Concatenate other)
    {
        this.intermediateResult.Append(other.intermediateResult);
    }

    /// <summary>
    /// Called at the end of aggregation, to return the results of the aggregation.
    /// </summary>
    /// <returns></returns>
    public SqlString Terminate()
    {
        string output = string.Empty;
        //delete the trailing comma, if any
        if (this.intermediateResult != null
            && this.intermediateResult.Length > 0)
        {
            output = this.intermediateResult.ToString(0, this.intermediateResult.Length - 1);
        }

        return new SqlString(output);
    }

    public void Read(BinaryReader r)
    {
        intermediateResult = new StringBuilder(r.ReadString());
    }

    public void Write(BinaryWriter w)
    {
        w.Write(this.intermediateResult.ToString());
    }
}

[Visual Basic]

Imports System
Imports System.Data
Imports Microsoft.SqlServer.Server
Imports System.Data.SqlTypes
Imports System.IO
Imports System.Text

<Serializable(), SqlUserDefinedAggregate(Format.UserDefined, IsInvariantToNulls:=True, IsInvariantToDuplicates:=False, IsInvariantToOrder:=False, MaxByteSize:=8000)> _
Public Class Concatenate
    Implements IBinarySerialize

    ''' <summary>
    ''' The variable that holds the intermediate result of the concatenation
    ''' </summary>
    Private intermediateResult As StringBuilder

    ''' <summary>
    ''' Initialize the internal data structures
    ''' </summary>
    Public Sub Init()
        Me.intermediateResult = New StringBuilder()
    End Sub

    ''' <summary>
    ''' Accumulate the next value, not if the value is null
    ''' </summary>
    ''' <param name="value"></param>
    Public Sub Accumulate(ByVal value As SqlString)
        If value.IsNull Then
            Return
        End If

        Me.intermediateResult.Append(value.Value).Append(","c)
    End Sub
    ''' <summary>
    ''' Merge the partially computed aggregate with this aggregate.
    ''' </summary>
    ''' <param name="other"></param>
    Public Sub Merge(ByVal other As Concatenate)
        Me.intermediateResult.Append(other.intermediateResult)
    End Sub

    ''' <summary>
    ''' Called at the end of aggregation, to return the results of the aggregation.
    ''' </summary>
    ''' <returns></returns>
    Public Function Terminate() As SqlString
        Dim output As String = String.Empty

        'delete the trailing comma, if any
        If Not (Me.intermediateResult Is Nothing) AndAlso Me.intermediateResult.Length > 0 Then
            output = Me.intermediateResult.ToString(0, Me.intermediateResult.Length - 1)
        End If

        Return New SqlString(output)
    End Function

    Public Sub Read(ByVal r As BinaryReader) Implements IBinarySerialize.Read
        intermediateResult = New StringBuilder(r.ReadString())
    End Sub

    Public Sub Write(ByVal w As BinaryWriter) Implements IBinarySerialize.Write
        w.Write(Me.intermediateResult.ToString())
    End Sub
End Class

코드를 MyAgg.dll로 컴파일한 후 다음과 같이 SQL Server에서 집계를 등록할 수 있습니다.

CREATE ASSEMBLY MyAgg FROM 'C:\MyAgg.dll';
GO
CREATE AGGREGATE MyAgg (@input nvarchar(200)) RETURNS nvarchar(max)
EXTERNAL NAME MyAgg.Concatenate;

[!참고]

/clr:pure 컴파일러 옵션을 사용하여 컴파일된 Visual C++ 데이터베이스 개체(예: 스칼라 반환 함수)는 SQL Server에서 실행할 수 없습니다.

대부분의 집계와 마찬가지로, 많은 논리가 Accumulate 메서드에 있습니다. 여기서 Accumulate 메서드에 매개 변수로 전달되는 문자열이 Init 메서드에서 초기화된 StringBuilder 개체에 추가됩니다. Accumulate 메서드가 처음으로 호출된 것이 아닐 경우 전달된 문자열을 추가하기 전에 StringBuilder에 쉼표도 추가됩니다. 계산 태스크를 마칠 때 Terminate 메서드가 호출되고 StringBuilder가 문자열로 반환됩니다.

예를 들어 다음 스키마가 있는 테이블을 고려해 보십시오.

CREATE TABLE BookAuthors
(
   BookID   int       NOT NULL,
   AuthorName    nvarchar(200) NOT NULL
);

그런 후에 다음 행을 삽입합니다.

INSERT BookAuthors VALUES(1, 'Johnson'),(2, 'Taylor'),(3, 'Steven'),(2, 'Mayler'),(3, 'Roberts'),(3, 'Michaels');

그러면 다음 쿼리는 다음과 같은 결과를 생성합니다.

SELECT BookID, dbo.MyAgg(AuthorName)
FROM BookAuthors
GROUP BY BookID;

BookID

작성자 이름

1

Johnson

2

Taylor, Mayler

3

Roberts, Michaels, Steven

예 2

다음 예제에서는 Accumulate 메서드에 매개 변수 두 개를 가진 집계를 보여 줍니다.

[C#]

using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;

[Serializable]
[SqlUserDefinedAggregate(
    Format.Native,
    IsInvariantToDuplicates = false,
    IsInvariantToNulls = true,
    IsInvariantToOrder = true,
    IsNullIfEmpty = true,
    Name = "WeightedAvg")]
public struct WeightedAvg
{
    /// <summary>
    /// The variable that holds the intermediate sum of all values multiplied by their weight
    /// </summary>
    private long sum;

    /// <summary>
    /// The variable that holds the intermediate sum of all weights
    /// </summary>
    private int count;

    /// <summary>
    /// Initialize the internal data structures
    /// </summary>
    public void Init()
    {
        sum = 0;
        count = 0;
    }

    /// <summary>
    /// Accumulate the next value, not if the value is null
    /// </summary>
    /// <param name="Value">Next value to be aggregated</param>
    /// <param name="Weight">The weight of the value passed to Value parameter</param>
    public void Accumulate(SqlInt32 Value, SqlInt32 Weight)
    {
        if (!Value.IsNull && !Weight.IsNull)
        {
            sum += (long)Value * (long)Weight;
            count += (int)Weight;
        }
    }

    /// <summary>
    /// Merge the partially computed aggregate with this aggregate
    /// </summary>
    /// <param name="Group">The other partial results to be merged</param>
    public void Merge(WeightedAvg Group)
    {
        sum += Group.sum;
        count += Group.count;
    }

    /// <summary>
    /// Called at the end of aggregation, to return the results of the aggregation.
    /// </summary>
    /// <returns>The weighted average of all inputed values</returns>
    public SqlInt32 Terminate()
    {
        if (count > 0)
        {
            int value = (int)(sum / count);
            return new SqlInt32(value);
        }
        else
        {
            return SqlInt32.Null;
        }
    }
}

[Visual Basic]

Imports System
Imports System.Data
Imports System.Data.SqlClient
Imports System.Data.SqlTypes
Imports Microsoft.SqlServer.Server
Imports System.Runtime.InteropServices

<StructLayout(LayoutKind.Sequential)> _
<Serializable(), SqlUserDefinedAggregate(Format.Native, _
IsInvariantToDuplicates:=False, _
IsInvariantToNulls:=True, _
IsInvariantToOrder:=True, _
IsNullIfEmpty:=True, _
Name:="WeightedAvg")> _
Public Class WeightedAvg

    ''' <summary>
    ''' The variable that holds the intermediate sum of all values multiplied by their weight
    ''' </summary>
    Private sum As Long

    ''' <summary>
    ''' The variable that holds the intermediate sum of all weights
    ''' </summary>
    Private count As Integer

    ''' <summary>
    ''' The variable that holds the intermediate sum of all weights
    ''' </summary>
    Public Sub Init()
        sum = 0
        count = 0
    End Sub

    ''' <summary>
    ''' Accumulate the next value, not if the value is null
    ''' </summary>
    ''' <param name="Value">Next value to be aggregated</param>
    ''' <param name="Weight">The weight of the value passed to Value parameter</param>
    Public Sub Accumulate(ByVal Value As SqlInt32, ByVal Weight As SqlInt32)
        If Not Value.IsNull AndAlso Not Weight.IsNull Then
            sum += CType(Value, Long) * CType(Weight, Long)
            count += CType(Weight, Integer)
        End If
    End Sub

    ''' <summary>
    ''' Merge the partially computed aggregate with this aggregate.
    ''' </summary>
    ''' <param name="Group">The other partial results to be merged</param>
    Public Sub Merge(ByVal Group As WeightedAvg)
        sum = Group.sum
        count = Group.count
    End Sub

    ''' <summary>
    ''' Called at the end of aggregation, to return the results of the aggregation.
    ''' </summary>
    ''' <returns>The weighted average of all inputed values</returns>
    Public Function Terminate() As SqlInt32
        If count > 0 Then
            ''                        int value = (int)(sum / count);
            ''          return new SqlInt32(value);
            Dim value As Integer = CType(sum / count, Integer)
            Return New SqlInt32(value)
        Else
            Return SqlInt32.Null
        End If
    End Function
End Class

C# 또는 Visual Basic 원본 코드를 컴파일한 후, 다음 Transact-SQL을 실행하십시오. 이 스크립트에서는 DLL을 WghtAvg.dll이라고 하고 C 드라이브의 루트 디렉터리에 있다고 가정합니다. 테스트라는 데이터베이스도 가정합니다.

use test;
go

-- sp_configure 'clr enabled', 1;
-- go

--- RECONFIGURE WITH OVERRIDE;
-- go

IF EXISTS (SELECT name FROM systypes WHERE name = 'MyTableType')
   DROP TYPE MyTableType;
go
   
IF EXISTS (SELECT name FROM sysobjects WHERE name = 'WeightedAvg')
   DROP AGGREGATE WeightedAvg;
go

IF EXISTS (SELECT name FROM sys.assemblies WHERE name = 'MyClrCode')
   DROP ASSEMBLY MyClrCode;
go

CREATE ASSEMBLY MyClrCode FROM 'C:\WghtAvg.dll';
GO

CREATE AGGREGATE WeightedAvg (@value int, @weight int) RETURNS int
EXTERNAL NAME MyClrCode.WeightedAvg;
go

CREATE TYPE MyTableType AS table (ItemValue int, ItemWeight int);
go

DECLARE @myTable AS MyTableType;

INSERT INTO @myTable VALUES(1, 4), (6, 1);

SELECT dbo.WeightedAvg(ItemValue, ItemWeight) FROM @myTable;
go

참고 항목

관련 자료

CLR 사용자 정의 집계