Question

我正在尝试通过在SQL SERVER中使用UDF来使查询可读，但是使用该功能时运行时间急剧增加。

以下是我正在使用的功能：

create function DL.trim_all(@input varchar(max)) 
returns varchar(max)
as begin 
    set @input=replace(replace(replace(@input,' ',''),')',''),'(','')
    return @input
end

代替写作：

SELECT
CASE WHEN replace(replace(replace([FULL_NAME_1],' ',''),')',''),'(','')=replace(replace(replace([FULL_NAME_2],' ',''),')',''),'(','') THEN 1 ELSE 0 END AS [name_match],
CASE WHEN replace(replace(replace([ADDRESS_1],' ',''),')',''),'(','')=replace(replace(replace([ADDRESS_2],' ',''),')',''),'(','') THEN 1 ELSE 0 END AS [adrs_match]
.
.
.
FROM
TABLE_1

用于20个不同的字段。

使用该功能时，运行时间为12.5分钟，而当不使用该功能时，运行时间为45秒。

有什么想法吗？

Answer 1

将John的想法再进一步一步，将标量函数转换为内联表函数，并使用cross apply为每对列激活它-您可能会获得更好的性能，但代价是查询更加麻烦：< / p>

CREATE function DL.DoesItMatch(@s1 varchar(500),@s2 varchar(500)) 
returns table -- returns a table with a single row and a single column
as return 
  SELECT 
    CASE WHEN replace(replace(replace(@s1,' ',''),')',''),'(','') = 
              replace(replace(replace(@s2,' ',''),')',''),'(','') THEN 1 ELSE 0 END As IsMatch;

和查询：

SELECT NameMatch.IsMatch AS [name_match],
       AddressMatch.IsMatch AS adrs_match
.
.
.
FROM TABLE_1
CROSS APPLY DL.DoesItMatch(FULL_NAME_1, FULL_NAME_2) As NameMatch
CROSS APPLY DL.DoesItMatch(ADDRESS_1, ADDRESS_2) As AddressMatch

Answer 2

无法想象巨大的提升，但是另一种方法呢

module.exports = {
  extend: 'apostrophe-pieces',
  name: xyz,
  label: xyz,
  addFields: [
    {
      name: 'latitude',
      label: 'latitude',
      type: 'string',
      required: true,
      readOnly: true
    }
  ]
}

然后将函数调用为：

create function DL.DoesItMatch(@s1 varchar(500),@s2 varchar(500)) 
returns bit
as begin 
    return CASE WHEN replace(replace(replace(@s1,' ',''),')',''),'(','')=replace(replace(replace(@s2,' ',''),')',''),'(','') THEN 1 ELSE 0 END
end

Answer 3

内联总是要走的路。期。即使不考虑限制并行性的T-SQL标量UDF的方面-ITVF速度更快，所需资源（CPU，内存和IO）更少，易于维护，并且更易于故障排除/分析/配置文件/跟踪。为了好玩，我进行了一项性能测试，将Zohar的ITVF与John的标量UDF进行了比较。我创建了25万行，针对两者都测试了一个基本选择，然后对堆进行了ORDER BY测试以强制排序。

样本数据：

-- Sample Data
BEGIN
  SET NOCOUNT ON;
  IF OBJECT_ID('tempdb..#tmp','U') IS NOT NULL DROP TABLE #tmp;
  SELECT TOP (250000) col1 = '('+LEFT(NEWID(),10)+')', col2 = '('+LEFT(NEWID(),10)+')'
  INTO    #tmp
  FROM   sys.all_columns a, sys.all_columns;

  UPDATE #tmp SET col1 = col2 WHERE LEFT(col1,2) = LEFT(col2,2) 
END

性能测试：

PRINT 'scalar, no sort'+CHAR(10)+REPLICATE('-',60);
GO
DECLARE @st DATETIME = GETDATE(), @isMatch BIT;
  SELECT @isMatch = DL.DoesItMatch(t.col1,t.col2)
  FROM   #tmp AS t;
PRINT DATEDIFF(MS,@st,GETDATE())
GO 3

PRINT CHAR(10)+'ITVF, no sort'+CHAR(10)+REPLICATE('-',60);
GO
DECLARE @st DATETIME = GETDATE(), @isMatch BIT;
  SELECT      @isMatch = f.isMatch
  FROM        #tmp AS t
  CROSS APPLY DL.DoesItMatch_ITVF(t.col1,t.col2) AS f;
PRINT DATEDIFF(MS,@st,GETDATE())
GO 3    

PRINT CHAR(10)+'scalar, sorted set'+CHAR(10)+REPLICATE('-',60);
GO
DECLARE @st DATETIME = GETDATE(), @isMatch BIT;
  SELECT @isMatch = DL.DoesItMatch(t.col1,t.col2)
  FROM   #tmp AS t
  ORDER BY DL.DoesItMatch(t.col1,t.col2);
PRINT DATEDIFF(MS,@st,GETDATE())
GO 3

PRINT CHAR(10)+'ITVF, sorted set'+CHAR(10)+REPLICATE('-',60);
GO
DECLARE @st DATETIME = GETDATE(), @isMatch BIT;
  SELECT      @isMatch = f.isMatch
  FROM        #tmp AS t
  CROSS APPLY DL.DoesItMatch_ITVF(t.col1,t.col2) AS f
  ORDER BY    f.isMatch;
PRINT DATEDIFF(MS,@st,GETDATE())
GO 3

测试结果：

scalar, no sort
------------------------------------------------------------
Beginning execution loop
844
843
840
Batch execution completed 3 times.

ITVF, no sort
------------------------------------------------------------
Beginning execution loop
270
270
270
Batch execution completed 3 times.

scalar, sorted set
------------------------------------------------------------
Beginning execution loop
937
930
936
Batch execution completed 3 times.

ITVF, sorted set
------------------------------------------------------------
Beginning execution loop
196
190
190
Batch execution completed 3 times.

因此，当不需要并行计划时，ITVF快3倍，而当需要并行计划时，它快5倍。这是我测试过ITVF与（标量和多语句表值UDF）的其他一些链接。

Set based plan runs slower than scalar valued function with many conditions

SQL Server user defined function to calculate age bracket

Function is slow but query runs fast

Why does SQL Server say this function is nondeterministic?

Grouping based on the match percentage

SQL Server 2008 user defined function to add spaces between each digit Sql table comma separated values contain any of variable values checking

SQL String manipulation, find all permutations

Answer 4

您可以在SQL Server 2019中使用Scalar UDF内联。这样，您将能够保留您编写的相同UDF，并自动获得与没有UDF的查询相同的性能。

您提供的UDF符合可嵌入性的标准，因此您的身体状况良好。有关UDF内联功能的文档位于：https://docs.microsoft.com/en-us/sql/relational-databases/user-defined-functions/scalar-udf-inlining?view=azuresqldb-current

专业提示：我建议您在使用Scalar UDF内联之前对UDF进行较小的修改。通过避免局部变量，使其成为单个语句标量UDF。这样，您比使用带有交叉应用的嵌入式TVF更好。

T-SQL UDF与完整表达式运行时

4 个答案: