सिंगल रिटर्न वैल्यू के लिए टेबल वैल्यूड फंक्शन बनाम स्केलर वैल्यू फंक्शन

जोनाथा डिकिंसन के साथ मेरी चर्चा (उनके उत्तर को देखें) ने मुझे कुछ त्वरित परीक्षण करने के लिए प्रेरित किया:

यह पता चला है, कि शुद्ध,एम्बेडेड स्केलर उप-चयन इतना बुरा नहीं है। केवल एक मान क्वेरी करना यह और भी तेज़ है . जैसा कि अपेक्षित था अदिश समारोह खराब है। TVF द्वारा जितने अधिक क्षेत्र वापस दिए जाते हैं, सापेक्ष प्रदर्शन उतना ही बेहतर होता है।

एकमात्र निश्चित उत्तर है:स्केलर फ़ंक्शन सबसे खराब है और एक बहु-पंक्ति TVF है - अधिकांश समय - इनलाइन की तुलना में धीमा। कोई भी तदर्थ दृष्टिकोण अधिक तेज़ होता है ।

लेकिन मैं सभी स्थितियों (स्केलर फ़ंक्शन को छोड़कर) के लिए विशेष मामले सेट कर सकता था, जहां एक दृष्टिकोण सबसे तेज़ था।

निष्कर्ष:(हमेशा की तरह :-)) यह निर्भर करता है...

संकेत:इसे कई तालिकाओं और स्तंभों वाले बड़े डेटाबेस के विरुद्ध जाने देना सबसे अच्छा है।

CREATE FUNCTION dbo.CountColumnScalar(@TableSchema AS VARCHAR(100),@TableName AS VARCHAR(100))
RETURNS INT
AS
BEGIN
    RETURN(SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS AS c WHERE [email protected] AND [email protected]);
END
GO
CREATE FUNCTION dbo.CountConstraintScalar(@TableSchema AS VARCHAR(100),@TableName AS VARCHAR(100))
RETURNS INT
AS
BEGIN
    RETURN(SELECT COUNT(*) FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE AS c WHERE [email protected] AND [email protected]);
END
GO

CREATE FUNCTION dbo.CountAllTVF(@TableSchema AS VARCHAR(100),@TableName AS VARCHAR(100))
RETURNS TABLE
RETURN SELECT (SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS AS c WHERE [email protected] AND [email protected] GROUP BY c.TABLE_SCHEMA,c.TABLE_NAME) AS ColCounter
             ,(SELECT COUNT(*) FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE AS c WHERE [email protected] AND [email protected] GROUP BY c.TABLE_SCHEMA,c.TABLE_NAME) AS ConstraintCounter    ;
GO
CREATE FUNCTION dbo.CountAllTVF_multiline(@TableSchema AS VARCHAR(100),@TableName AS VARCHAR(100))
RETURNS @tbl TABLE (ColCounter INT,ConstraintCounter INT)
AS
BEGIN
INSERT INTO @tbl
SELECT (SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS AS c WHERE [email protected] AND [email protected] GROUP BY c.TABLE_SCHEMA,c.TABLE_NAME) AS ColCounter
      ,(SELECT COUNT(*) FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE AS c WHERE [email protected] AND [email protected] GROUP BY c.TABLE_SCHEMA,c.TABLE_NAME) AS ConstraintCounter;
RETURN;
END
GO

DECLARE @time DATETIME=GETDATE();
SELECT TABLE_SCHEMA,TABLE_NAME
     ,(SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS AS c WHERE c.TABLE_SCHEMA=t.TABLE_SCHEMA AND c.TABLE_NAME=t.TABLE_NAME ) AS ColCounter
     ,(SELECT COUNT(*) FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE AS c WHERE c.TABLE_SCHEMA=t.TABLE_SCHEMA AND c.TABLE_NAME=t.TABLE_NAME ) AS ConstraintCounter
FROM INFORMATION_SCHEMA.TABLES AS t;
PRINT 'pure embedded scalar sub-select: ' + CAST(CAST(GETDATE()[email protected] AS TIME) AS VARCHAR(MAX)); SET @time=GETDATE();


SELECT TABLE_SCHEMA,TABLE_NAME
     ,dbo.CountColumnScalar(t.TABLE_SCHEMA,t.TABLE_NAME ) AS ColCounter 
     ,dbo.CountConstraintScalar(t.TABLE_SCHEMA,t.TABLE_NAME ) AS ConstraintCount 
FROM INFORMATION_SCHEMA.TABLES AS t
PRINT 'scalar function: ' + CAST(CAST(GETDATE()[email protected] AS TIME) AS VARCHAR(MAX)); SET @time=GETDATE();


SELECT t.TABLE_SCHEMA,t.TABLE_NAME
      ,colJoin.ColCount
      ,conJoin.ConstraintCount 
FROM INFORMATION_SCHEMA.TABLES AS t
INNER JOIN (SELECT COUNT(*) As ColCount,c.TABLE_SCHEMA,c.TABLE_NAME 
            FROM INFORMATION_SCHEMA.COLUMNS AS c 
            GROUP BY c.TABLE_SCHEMA,c.TABLE_NAME) AS colJoin ON  colJoin.TABLE_SCHEMA=t.TABLE_SCHEMA AND colJoin.TABLE_NAME=t.TABLE_NAME
INNER JOIN (SELECT COUNT(*) As ConstraintCount,c.TABLE_SCHEMA,c.TABLE_NAME 
            FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE AS c 
            GROUP BY c.TABLE_SCHEMA,c.TABLE_NAME) AS conJoin ON  conJoin.TABLE_SCHEMA=t.TABLE_SCHEMA AND conJoin.TABLE_NAME=t.TABLE_NAME
PRINT 'JOINs on sub-selects: ' + CAST(CAST(GETDATE()[email protected] AS TIME) AS VARCHAR(MAX)); SET @time=GETDATE();

SELECT t.TABLE_SCHEMA,t.TABLE_NAME
      ,ColCounter.*
FROM INFORMATION_SCHEMA.TABLES AS t
CROSS APPLY dbo.CountAllTVF(t.TABLE_SCHEMA,t.TABLE_NAME) AS ColCounter
PRINT 'TVF inline: ' + CAST(CAST(GETDATE()[email protected] AS TIME) AS VARCHAR(MAX)); SET @time=GETDATE();


SELECT t.TABLE_SCHEMA,t.TABLE_NAME
      ,ColCounter.*
FROM INFORMATION_SCHEMA.TABLES AS t
CROSS APPLY dbo.CountAllTVF_multiline(t.TABLE_SCHEMA,t.TABLE_NAME) AS ColCounter
PRINT 'TVF multiline: ' + CAST(CAST(GETDATE()[email protected] AS TIME) AS VARCHAR(MAX)); SET @time=GETDATE();
GO

DROP FUNCTION dbo.CountColumnScalar;
DROP FUNCTION dbo.CountAllTVF;
DROP FUNCTION dbo.CountAllTVF_multiline;
DROP FUNCTION dbo.CountConstraintScalar;