SQL 語句在查詢分析器執行很快，程序 Dapper 參數化查詢就很慢（parameter-sniffing）

這個問題困擾我好長時間了，使用SQLSERVER 事務探查器找到執行超時的SQL語句，參數查詢都是通過執行exe sp_executesql 的存儲過程調用，因為它能夠分析並緩存查詢計划，從而優化查詢效率，但是現在反而很慢。本地調試沒有問題，開始上線也沒有問題，但是運行一個月左右有時候會出現超時現象：
Timeout expired.  The timeout period elapsed prior to completion of the operation or the server is not responding.

 

                var param = new DynamicParameters();
                param.Add("@StDateNum", Convert.ToInt32(dStartDate.ToString("yyyyMMdd")), dbType: DbType.Int32);
                param.Add("@EndDateNum", Convert.ToInt32(dEndDate.ToString("yyyyMMdd")), dbType: DbType.Int32);
                param.Add("@StDate", dStartDate, dbType: DbType.DateTime);
                param.Add("@EdDate", dEndDate, dbType: DbType.DateTime);
                param.Add("@HotelCd", sHotelCd, dbType: DbType.AnsiString, size: sHotelCd.Length);
                return new SqlConnection(DBSetting.PriceAndRmFlow).Query<PriceAndRmFlow>(cmdText, param).ToList();

 

臨時解決辦法

1.就是把代碼DbType重新指定不同類型，重新部署就好了，但根本原因還是沒有找到。網上也看了好多文章，說是是參數類型不正確，必須設定為數據庫一致的參數類型。另外Size也有影響，使用參數化后,因為字段類型錯誤導致了表掃描。已做修改，還在觀察中。

2.看了幾篇文章，初步分析是因為執行計划的問題，后面在SQL后面強制禁用了重用執行計划( OPTION (RECOMPILE))，本來想分析了SQL的執行計划，但是之前同樣慢的SQL，查詢起來又很快了。

3.可能是緩存不好的緩存計划，可以執行 DBCC FREEPROCCACHE 清除。

4.在這篇文章 http://stackoverflow.com/questions/10933366/sp-executesql-is-slow-with-parameters 中並且也用的是Dapper，解決方式是加了 WITH RECOMPILE 語句

parameter-sniffing

• Query runs fast, but runs slow in stored procedure
• SQL Server: Query fast, but slow from procedure
• Query times out when executed from web, but super-fast when executed from SSMS

SQL Server Management Studio 的默認 ARITHABORT 設置為 ON。 客戶端應用程序將 ARITHABORT 設置為 OFF 可以接收不同的查詢計划，使得對性能較差的查詢進行故障排除變得困難。 即，同一個查詢可以在 Management Studio 中快速執行，但在應用程序中卻比較慢。 使用 Management Studio 排除查詢故障時始終與客戶端 ARITHABORT 設置匹配。

查詢執行計划

select * from sys.dm_exec_cached_plans
cross apply sys.dm_exec_sql_text(plan_handle) t ORDER BY sys.dm_exec_cached_plans.usecounts DESC

System.Data.DbType映射關系

AnsiString:VarChar Binary:VarBinary Byte:TinyInt Boolean:Bit Currency:Money Date:DateTime DateTime:DateTime Decimal:Decimal Double:Float Guid:UniqueIdentifier Int16:SmallInt Int32:Int Int64:BigInt Object:Variant Single:Real String:NVarChar Time:DateTime AnsiStringFixedLength:Char StringFixedLength:NChar Xml:Xml DateTime2:DateTime2 DateTimeOffset:DateTimeOffset

 

=========== System.Data.SqlClient.SqlDbType =========

System

.Data.SqlClient.SqlDbType.BigInt(0) = System.Data.DbType.Int64(12)

System

.Data.SqlClient.SqlDbType.Binary(1) = System.Data.DbType.Binary(1)

System

.Data.SqlClient.SqlDbType.Bit(2) = System.Data.DbType.Boolean(3)

System

.Data.SqlClient.SqlDbType.Char(3) = System.Data.DbType.AnsiStringFixedLength(22)

System

.Data.SqlClient.SqlDbType.DateTime(4) = System.Data.DbType.DateTime(6)

System

.Data.SqlClient.SqlDbType.Decimal(5) = System.Data.DbType.Decimal(7)

System

.Data.SqlClient.SqlDbType.Float(6) = System.Data.DbType.Double(8)

System

.Data.SqlClient.SqlDbType.Image(7) = System.Data.DbType.Binary(1)

System

.Data.SqlClient.SqlDbType.Int(8) = System.Data.DbType.Int32(11)

System

.Data.SqlClient.SqlDbType.Money(9) = System.Data.DbType.Currency(4)

System

.Data.SqlClient.SqlDbType.NChar(10) = System.Data.DbType.StringFixedLength(23)

System

.Data.SqlClient.SqlDbType.NText(11) = System.Data.DbType.String(16)

System

.Data.SqlClient.SqlDbType.NVarChar(12) = System.Data.DbType.String(16)

System

.Data.SqlClient.SqlDbType.Real(13) = System.Data.DbType.Single(15)

System

.Data.SqlClient.SqlDbType.UniqueIdentifier(14) = System.Data.DbType.Guid(9)

System

.Data.SqlClient.SqlDbType.SmallDateTime(15) = System.Data.DbType.DateTime(6)

System

.Data.SqlClient.SqlDbType.SmallInt(16) = System.Data.DbType.Int16(10)

System

.Data.SqlClient.SqlDbType.SmallMoney(17) = System.Data.DbType.Currency(4)

System

.Data.SqlClient.SqlDbType.Text(18) = System.Data.DbType.AnsiString(0)

System

.Data.SqlClient.SqlDbType.Timestamp(19) = System.Data.DbType.Binary(1)

System

.Data.SqlClient.SqlDbType.TinyInt(20) = System.Data.DbType.Byte(2)

System

.Data.SqlClient.SqlDbType.VarBinary(21) = System.Data.DbType.Binary(1)

System

.Data.SqlClient.SqlDbType.VarChar(22) = System.Data.DbType.AnsiString(0)

System

.Data.SqlClient.SqlDbType.Variant(23) = System.Data.DbType.Object(13)

System

.Data.SqlClient.SqlDbType.Xml(25) = System.Data.DbType.Xml(25)

System

.Data.SqlClient.SqlDbType.Udt(29) = System.Data.DbType.Object(13)

System

.Data.SqlClient.SqlDbType.Structured(30) = System.Data.DbType.Object(13)

System

.Data.SqlClient.SqlDbType.Date(31) = System.Data.DbType.Date(5)

System

.Data.SqlClient.SqlDbType.Time(32) = System.Data.DbType.Time(17)

System

.Data.SqlClient.SqlDbType.DateTime2(33) = System.Data.DbType.DateTime2(26)

System

.Data.SqlClient.SqlDbType.DateTimeOffset(34) = System.Data.DbType.DateTimeOffset(27) ===========System.Data.OleDb.OleDbType=========

System

.Data.OleDb.OleDbType.Empty(0) = System.Data.DbType.Object(13)

System

.Data.OleDb.OleDbType.SmallInt(2) = System.Data.DbType.Int16(10)

System

.Data.OleDb.OleDbType.Integer(3) = System.Data.DbType.Int32(11)

System

.Data.OleDb.OleDbType.Single(4) = System.Data.DbType.Single(15)

System

.Data.OleDb.OleDbType.Double(5) = System.Data.DbType.Double(8)

System

.Data.OleDb.OleDbType.Currency(6) = System.Data.DbType.Currency(4)

System

.Data.OleDb.OleDbType.Date(7) = System.Data.DbType.DateTime(6)

System

.Data.OleDb.OleDbType.BSTR(8) = System.Data.DbType.String(16)

System

.Data.OleDb.OleDbType.IDispatch(9) = System.Data.DbType.Object(13)

System

.Data.OleDb.OleDbType.Error(10) = System.Data.DbType.Int32(11)

System

.Data.OleDb.OleDbType.Boolean(11) = System.Data.DbType.Boolean(3)

System

.Data.OleDb.OleDbType.Variant(12) = System.Data.DbType.Object(13)

System

.Data.OleDb.OleDbType.IUnknown(13) = System.Data.DbType.Object(13)

System

.Data.OleDb.OleDbType.Decimal(14) = System.Data.DbType.Decimal(7)

System

.Data.OleDb.OleDbType.TinyInt(16) = System.Data.DbType.SByte(14)

System

.Data.OleDb.OleDbType.UnsignedTinyInt(17) = System.Data.DbType.Byte(2)

System

.Data.OleDb.OleDbType.UnsignedSmallInt(18) = System.Data.DbType.UInt16(18)

System

.Data.OleDb.OleDbType.UnsignedInt(19) = System.Data.DbType.UInt32(19)

System

.Data.OleDb.OleDbType.BigInt(20) = System.Data.DbType.Int64(12)

System

.Data.OleDb.OleDbType.UnsignedBigInt(21) = System.Data.DbType.UInt64(20)

System

.Data.OleDb.OleDbType.Filetime(64) = System.Data.DbType.DateTime(6)

System

.Data.OleDb.OleDbType.Guid(72) = System.Data.DbType.Guid(9)

System

.Data.OleDb.OleDbType.Binary(128) = System.Data.DbType.Binary(1)

System

.Data.OleDb.OleDbType.Char(129) = System.Data.DbType.AnsiStringFixedLength(22)

System

.Data.OleDb.OleDbType.WChar(130) = System.Data.DbType.StringFixedLength(23)

System

.Data.OleDb.OleDbType.Numeric(131) = System.Data.DbType.Decimal(7)

System

.Data.OleDb.OleDbType.DBDate(133) = System.Data.DbType.Date(5)

System

.Data.OleDb.OleDbType.DBTime(134) = System.Data.DbType.Time(17)

System

.Data.OleDb.OleDbType.DBTimeStamp(135) = System.Data.DbType.DateTime(6)

System

.Data.OleDb.OleDbType.PropVariant(138) = System.Data.DbType.Object(13)

System

.Data.OleDb.OleDbType.VarNumeric(139) = System.Data.DbType.VarNumeric(21)

System

.Data.OleDb.OleDbType.VarChar(200) = System.Data.DbType.AnsiString(0)

System

.Data.OleDb.OleDbType.LongVarChar(201) = System.Data.DbType.AnsiString(0)

System

.Data.OleDb.OleDbType.VarWChar(202) = System.Data.DbType.String(16)

System

.Data.OleDb.OleDbType.LongVarWChar(203) = System.Data.DbType.String(16)

System

.Data.OleDb.OleDbType.VarBinary(204) = System.Data.DbType.Binary(1)

System

.Data.OleDb.OleDbType.LongVarBinary(205) = System.Data.DbType.Binary(1) =========System.Data.Odbc.OdbcType===========

System

.Data.Odbc.OdbcType.BigInt(1) = System.Data.DbType.Int64(12)

System

.Data.Odbc.OdbcType.Binary(2) = System.Data.DbType.Binary(1)

System

.Data.Odbc.OdbcType.Bit(3) = System.Data.DbType.Boolean(3)

System

.Data.Odbc.OdbcType.Char(4) = System.Data.DbType.AnsiStringFixedLength(22)

System

.Data.Odbc.OdbcType.DateTime(5) = System.Data.DbType.DateTime(6)

System

.Data.Odbc.OdbcType.Decimal(6) = System.Data.DbType.Decimal(7)

System

.Data.Odbc.OdbcType.Numeric(7) = System.Data.DbType.Decimal(7)

System

.Data.Odbc.OdbcType.Double(8) = System.Data.DbType.Double(8)

System

.Data.Odbc.OdbcType.Image(9) = System.Data.DbType.Binary(1)

System

.Data.Odbc.OdbcType.Int(10) = System.Data.DbType.Int32(11)

System

.Data.Odbc.OdbcType.NChar(11) = System.Data.DbType.StringFixedLength(23)

System

.Data.Odbc.OdbcType.NText(12) = System.Data.DbType.String(16)

System

.Data.Odbc.OdbcType.NVarChar(13) = System.Data.DbType.String(16)

System

.Data.Odbc.OdbcType.Real(14) = System.Data.DbType.Single(15)

System

.Data.Odbc.OdbcType.UniqueIdentifier(15) = System.Data.DbType.Guid(9)

System

.Data.Odbc.OdbcType.SmallDateTime(16) = System.Data.DbType.DateTime(6)

System

.Data.Odbc.OdbcType.SmallInt(17) = System.Data.DbType.Int16(10)

System

.Data.Odbc.OdbcType.Text(18) = System.Data.DbType.AnsiString(0)

System

.Data.Odbc.OdbcType.Timestamp(19) = System.Data.DbType.Binary(1)

System

.Data.Odbc.OdbcType.TinyInt(20) = System.Data.DbType.Byte(2)

System

.Data.Odbc.OdbcType.VarBinary(21) = System.Data.DbType.Binary(1)

System

.Data.Odbc.OdbcType.VarChar(22) = System.Data.DbType.AnsiString(0)

System

.Data.Odbc.OdbcType.Date(23) = System.Data.DbType.Date(5)

System

.Data.Odbc.OdbcType.Time(24) = System.Data.DbType.Time(17) =========System.Data.OracleClient.OracleType===========

System

.Data.OracleClient.OracleType.BFile(1) = System.Data.DbType.Binary(1)

System

.Data.OracleClient.OracleType.Blob(2) = System.Data.DbType.Binary(1)

System

.Data.OracleClient.OracleType.Char(3) = System.Data.DbType.AnsiStringFixedLength(22)

System

.Data.OracleClient.OracleType.Clob(4) = System.Data.DbType.AnsiString(0)

System

.Data.OracleClient.OracleType.Cursor(5) = System.Data.DbType.Object(13)

System

.Data.OracleClient.OracleType.DateTime(6) = System.Data.DbType.DateTime(6)

System

.Data.OracleClient.OracleType.IntervalDayToSecond(7) = System.Data.DbType.Object(13)

System

.Data.OracleClient.OracleType.IntervalYearToMonth(8) = System.Data.DbType.Int32(11)

System

.Data.OracleClient.OracleType.LongRaw(9) = System.Data.DbType.Binary(1)

System

.Data.OracleClient.OracleType.LongVarChar(10) = System.Data.DbType.AnsiString(0)

System

.Data.OracleClient.OracleType.NChar(11) = System.Data.DbType.StringFixedLength(23)

System

.Data.OracleClient.OracleType.NClob(12) = System.Data.DbType.String(16)

System

.Data.OracleClient.OracleType.Number(13) = System.Data.DbType.VarNumeric(21)

System

.Data.OracleClient.OracleType.NVarChar(14) = System.Data.DbType.String(16)

System

.Data.OracleClient.OracleType.Raw(15) = System.Data.DbType.Binary(1)

System

.Data.OracleClient.OracleType.RowId(16) = System.Data.DbType.AnsiString(0)

System

.Data.OracleClient.OracleType.Timestamp(18) = System.Data.DbType.DateTime(6)

System

.Data.OracleClient.OracleType.TimestampLocal(19) = System.Data.DbType.DateTime(6)

System

.Data.OracleClient.OracleType.TimestampWithTZ(20) = System.Data.DbType.DateTime(6)

System

.Data.OracleClient.OracleType.VarChar(22) = System.Data.DbType.AnsiString(0)

System

.Data.OracleClient.OracleType.Byte(23) = System.Data.DbType.Byte(2)

System

.Data.OracleClient.OracleType.UInt16(24) = System.Data.DbType.UInt16(18)

System

.Data.OracleClient.OracleType.UInt32(25) = System.Data.DbType.UInt32(19)

System

.Data.OracleClient.OracleType.SByte(26) = System.Data.DbType.SByte(14)

System

.Data.OracleClient.OracleType.Int16(27) = System.Data.DbType.Int16(10)

System

.Data.OracleClient.OracleType.Int32(28) = System.Data.DbType.Int32(11)

System

.Data.OracleClient.OracleType.Float(29) = System.Data.DbType.Single(15)

System

.Data.OracleClient.OracleType.Double(30) = System.Data.DbType.Double(8)

 

 

Refer:
實例化SqlParameter時，如果是字符型，一定要指定size屬性
http://bbs.csdn.net/topics/380155255
為什么@SN varchar類型的和@SN1 nvarchar類型會有這樣的差別？
http://bbs.csdn.net/topics/380126782
參數化查詢比拼接字符串慢的原因
http://www.cnblogs.com/fxwdl/archive/2008/07/31/1257409.html
同樣的SQL語句在查詢分析器執行很快，但是網站上執行超時的詭異問題
http://www.cnblogs.com/bluedoctor/archive/2011/03/04/1970866.html
高分求解！為什么拼接的SQL語句比參數化的查詢快？？？
http://bbs.csdn.net/topics/390399686
Data Type Precedence (Transact-SQL)
http://msdn.microsoft.com/en-us/library/ms190309.aspx
what-is-parameter-sniffing
http://blogs.technet.com/b/mdegre/archive/2012/03/19/what-is-parameter-sniffing.aspx
How Data Access Code Affects Database Performance
http://msdn.microsoft.com/en-us/magazine/ee236412.aspx
http://stackoverflow.com/questions/25159051/non-optimal-execution-plan-using-sp-executesql
Slow in the Application, Fast in SSMS ?
http://www.sommarskog.se/query-plan-mysteries.html
parameter-sniffing
https://www.simple-talk.com/sql/t-sql-programming/parameter-sniffing
http://pratchev.blogspot.be/2007/08/parameter-sniffing.html
http://omnibuzz-sql.blogspot.com/2006/11/parameter-sniffing-stored-procedures.html
http://stackoverflow.com/search?q=Parameter+sniffing