Compare String function in mysql by words - mysql

Question

I am trying to create a search function in mysql. In order to make the search result more reliability i need to compare two string by words. Inputs are 2 strings and output is number word two strings match. In MySql i did as below.
CREATE DEFINER=`root`#`localhost` FUNCTION `CompareStrings`(str1 VARCHAR(255),str2 VARCHAR(255)) RETURNS double
BEGIN
DECLARE cur_position INT DEFAULT 1 ;
DECLARE remainder TEXT;
DECLARE cur_string VARCHAR(50);
DECLARE delimiter_length TINYINT UNSIGNED;
DECLARE numberMatch INT;
DECLARE total INT;
DECLARE result DOUBLE DEFAULT 0;
DECLARE delim VARCHAR(10);
DECLARE string2 VARCHAR(255);
SET delim = ' ';
DROP TEMPORARY TABLE IF EXISTS SplitString1;
CREATE TEMPORARY TABLE SplitString1 (
SplitString1ID INT NOT NULL PRIMARY KEY AUTO_INCREMENT ,
val VARCHAR(50) NOT NULL
) ENGINE=MyISAM;
DROP TEMPORARY TABLE IF EXISTS SplitString2;
CREATE TEMPORARY TABLE SplitString2 (
SplitString1ID INT NOT NULL PRIMARY KEY AUTO_INCREMENT ,
val VARCHAR(50) NOT NULL
) ENGINE=MyISAM;
SET remainder = str1;
SET delimiter_length = CHAR_LENGTH(delim);
WHILE CHAR_LENGTH(remainder) > 0 AND cur_position > 0 DO
SET cur_position = INSTR(remainder, delim);
IF cur_position = 0 THEN
SET cur_string = remainder;
ELSE
SET cur_string = LEFT(remainder, cur_position - 1);
END IF;
IF TRIM(cur_string) != '' THEN
INSERT INTO SplitString1(val) VALUES (cur_string);
END IF;
SET remainder = SUBSTRING(remainder, cur_position + delimiter_length);
END WHILE;
SET remainder = str2;
SET cur_position = 1;
WHILE CHAR_LENGTH(remainder) > 0 AND cur_position > 0 DO
SET cur_position = INSTR(remainder, delim);
IF cur_position = 0 THEN
SET cur_string = remainder;
ELSE
SET cur_string = LEFT(remainder, cur_position - 1);
END IF;
IF TRIM(cur_string) != '' THEN
INSERT INTO SplitString2(val) VALUES (cur_string);
END IF;
SET remainder = SUBSTRING(remainder, cur_position + delimiter_length);
END WHILE;
SELECT count(*) INTO numberMatch
FROM SplitString1 s1 JOIN SplitString2 s2 ON s1.val = s2.val;
RETURN result;
END
The idea is create two temporary table store each word and then compare these 2 tables. The result is good but the performace is awful. Anybody has better idea, please give me an advice.
Many thanks!

Answer 1

I don't think this will work as stated.
The logic is sound but you have not assigned any value to your result variable. Hence this function will always return 0. Replace:
RETURN result;
with
RETURN numberMatch;
Also replace:
CREATE DEFINER=`root`#`localhost` FUNCTION `CompareStrings`(str1 VARCHAR(255),str2 VARCHAR(255)) RETURNS double
with
CREATE DEFINER=`root`#`localhost` FUNCTION `CompareStrings`(str1 VARCHAR(255),str2 VARCHAR(255)) RETURNS double READS SQL DATA
As far as efficiency goes it looks pretty efficient. When you say 'performance is awful' - what constitutes 'awful'? Have you got any benchmark figures e.g. x calls took y millis?