All posts tagged performance

The original post appeared here:

http://sqlblog.com/blogs/adam_machanic/archive/2009/04/28/sqlclr-string-splitting-part-2-even-faster-even-more-scalable.aspx

Please visit the original website for more discussion, this is for reference purpose only.

 

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

public partial class UserDefinedFunctions
{
[Microsoft.SqlServer.Server.SqlFunction(
FillRowMethodName = "FillRow_Multi",
TableDefinition = "item nvarchar(4000)"
)
]
public static IEnumerator SplitString_Multi(
[SqlFacet(MaxSize = -1)]
SqlChars Input,
[SqlFacet(MaxSize = 255)]
SqlChars Delimiter
)
{
return (
(Input.IsNull || Delimiter.IsNull) ?
new SplitStringMulti(new char[0], new char[0]) :
new SplitStringMulti(Input.Value, Delimiter.Value));
}

public static void FillRow_Multi(object obj, out SqlString item)
{
item = new SqlString((string)obj);
}

public class SplitStringMulti : IEnumerator
{
public SplitStringMulti(char[] TheString, char[] Delimiter)
{
theString = TheString;
stringLen = TheString.Length;
delimiter = Delimiter;
delimiterLen = (byte)(Delimiter.Length);
isSingleCharDelim = (delimiterLen == 1);

lastPos = 0;
nextPos = delimiterLen * -1;
}

#region IEnumerator Members

public object Current
{
get
{
return new string(theString, lastPos, nextPos - lastPos);
}
}

public bool MoveNext()
{
if (nextPos >= stringLen)
return false;
else
{
lastPos = nextPos + delimiterLen;

for (int i = lastPos; i < stringLen; i++)
{
bool matches = true;

//Optimize for single-character delimiters
if (isSingleCharDelim)
{
if (theString[i] != delimiter[0])
matches = false;
}
else
{
for (byte j = 0; j < delimiterLen; j++)
{
if (((i + j) >= stringLen) || (theString[i + j] != delimiter[j]))
{
matches = false;
break;
}
}
}

if (matches)
{
nextPos = i;

//Deal with consecutive delimiters
if ((nextPos - lastPos) > 0)
return true;
else
{
i += (delimiterLen-1);
lastPos += delimiterLen;
}
}
}

lastPos = nextPos + delimiterLen;
nextPos = stringLen;

if ((nextPos - lastPos) > 0)
return true;
else
return false;
}
}

public void Reset()
{
lastPos = 0;
nextPos = delimiterLen * -1;
}

#endregion

private int lastPos;
private int nextPos;

private readonly char[] theString;
private readonly char[] delimiter;
private readonly int stringLen;
private readonly byte delimiterLen;
private readonly bool isSingleCharDelim;
}
};