オプションのパラメータを指定できるようにしたいので、メソッドをオーバーロードできますか?Accumulate()
区切り文字を指定できるようにオーバーロードしたいのですが、区切り文字を強制的に指定する必要がある他の人を見てきましたが、この動作は適していません。
CREATE AGGREGATE dbo.Concatenate (@input nvarchar(max), <OPTIONAL PARAMETER HERE>)
RETURNS nvarchar(max)
Accumulate()
参考までに、オーバーロードしようとしているメソッドを含む集約クラス コードを次に示します。
using System;
using System.Data;
using Microsoft.SqlServer.Server;
using System.Data.SqlTypes;
using System.IO;
using System.Text;
namespace CLR.Utilities {
/// <summary>
/// <list type="references">
/// <reference>
/// <name>How to: Create and Run a CLR SQL Server Aggregate</name>
/// <link>http://msdn.microsoft.com/en-us/library/91e6taax(v=vs.90).aspx</link>
/// </reference>
/// <reference>
/// <name>SqlUserDefinedAggregateAttribute</name>
/// <link>http://msdn.microsoft.com/en-us/library/microsoft.sqlserver.server.sqluserdefinedaggregateattribute(v=vs.90).aspx</link>
/// </reference>
/// <reference>
/// <name>Invoking CLR User-Defined Aggregate Functions (Provides seed code for this function)</name>
/// <link>http://technet.microsoft.com/en-us/library/ms131056.aspx</link>
/// </reference>
/// </list>
/// </summary>
[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 = -1) //no 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([SqlFacet(MaxSize = -1)] SqlString value) {
if (value.IsNull) {
return;
}
this.intermediateResult.Append(value.Value.Trim()).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>
[return: SqlFacet(MaxSize = -1)]
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).Trim();
}
return new SqlString(output);
}
public void Read(BinaryReader r) {
intermediateResult = new StringBuilder(r.ReadString());
}
public void Write(BinaryWriter w) {
w.Write(this.intermediateResult.ToString().Trim());
}
}
}
また、オプションのパラメーターを設定できる場合にも変更したい展開用のコードは次のとおりです。
IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[Concatenate]') AND type = N'AF')
DROP AGGREGATE [dbo].[Concatenate]
GO
IF EXISTS (SELECT * FROM sys.assemblies asms WHERE asms.name = N'CLR.Utilities' and is_user_defined = 1)
DROP ASSEMBLY [CLR.Utilities]
GO
ALTER DATABASE [DatabaseName] SET TRUSTWORTHY ON
GO
CREATE ASSEMBLY [CLR.Utilities] FROM 'C:\Path\To\File\CLR.Utilities.dll' WITH PERMISSION_SET = UNSAFE
GO
CREATE AGGREGATE [dbo].[Concatenate] (@input nvarchar(max)) RETURNS nvarchar(max)
EXTERNAL NAME [CLR.Utilities].[CLR.Utilities.Concatenate]
GO
GRANT EXECUTE ON [dbo].[Concatenate] TO PUBLIC
GO