[转载]SqlServer怎样获取查询语句的成本

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[转载]SqlServer怎样获取查询语句的成本 – zzj8704 – 博客园.

在有些大系统中,客户端查询非常复杂,需要显示很多字段和过滤很多条件,例如TFS中的条件过滤,或则用户希望客户端查询能像EXCEL过滤那 样方便

这样可能导致查询语句非常复杂,此时的效率也比较低.

TFS查询条件界面:

如果可以获取查询语句的成本,当SQL语句执行成本很大(可能执行时间会很长时),系统自动提示用户是否继续或则大概需要多长时间,这样会提高用户 体验.

下举一例:

查询SQL Server中的所有列信息表:sys.all_columns

在Sql server 2k8 management studio 中先后执行下面每行语句即可得到Sql语句的成本, 即为第二个语句执行结果中第一行中TotalSubtreeCost字段值.

set showplan_all on
select * from sys.all_columns

第二个语句(select * from sys.all_columns)执行结果:

StmtText TotalSubtreeCost StmtId NodeId Parent PhysicalOp LogicalOp EstimateRows EstimateIO EstimateCPU AvgRowSize
select * from sys.all_columns 0.1736313 1 1 0 NULL NULL 5270 NULL NULL NULL
|–Concatenation 0.1736313 1 2 1 Concatenation Concatenation 5270 0 0.000527 303
0.01454595 1 3 2 Filter Filter 659 0 8.44E-04 303
0.01370243 1 4 3 Compute Scalar Compute Scalar 659 0 6.59E-05 305
0.01363653 1 5 4 Clustered Index Scan Clustered Index Scan 659 0.01275463 0.0008819 179
0.1585583 1 36 2 Compute Scalar Compute Scalar 4611 0 0.0004611 303
0.1523828 1 37 36 Compute Scalar Compute Scalar 4611 0 0.0011905 164
0.1511923 1 38 37 Clustered Index Scan Clustered Index Scan 4611 0.1379398 0.0132525 167

再执行 set showplan_all off结束查询计划分析结果.

此时可以应用showplan_all来获取Sql查询的成本.

如下为C#简单实现上述应用,在VS2k8中编译通过,只需正确更改Data Source即可运行:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;
using System.Data;
using System.Diagnostics;

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
SqlConnectionStringBuilder connectionBuilder = new SqlConnectionStringBuilder();
connectionBuilder.Add(“Data Source”, “your server name or ip“);
connectionBuilder.Add(“Initial Catalog”, “master”);
connectionBuilder.Add(“Integrated Security”, “True”);

string sqlStr = “select * from sys.all_columns”;
Console.WriteLine(GetSqlCost(connectionBuilder.ToString(), sqlStr).ToString());
Console.Read();
}

static double GetSqlCost(string connectStr, string strSQL)
{
double sqlCost;
int timeOut;
SqlDataAdapter adapter;
SqlConnection connection = new SqlConnection(connectStr);
SqlCommand command;
DataTable table;
timeOut = 180;
adapter = null;

try
{
connection.Open();
command = new SqlCommand(“set showplan_all on “, connection);
command.ExecuteNonQuery();
command.CommandText = strSQL;
adapter = new SqlDataAdapter(strSQL, connection);
adapter.SelectCommand.CommandTimeout = timeOut;
table = new DataTable();
adapter.Fill(table);
command.CommandText = “set showplan_all off”;
command.ExecuteNonQuery();
sqlCost = System.Convert.ToDouble(table.Rows[0][“TotalSubtreeCost”]);
}
finally
{
command = null;
connection.Close();
}
return sqlCost;
}
}

}

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