MYSQL Function gets progressively slower - mysql

Question

I created the following function to input records by parsing a string:
DROP FUNCTION IF EXISTS RowPerRow ;
DELIMITER $$
CREATE FUNCTION RowPerRow()
RETURNS VARCHAR(300)
BEGIN
DECLARE n INT DEFAULT 0 ;
DECLARE m INT DEFAULT 0 ;
DECLARE i INT DEFAULT 0 ;
DECLARE j INT DEFAULT 0 ;
SELECT count(*) FROM Temp0 INTO n ;
WHILE i < n DO
SELECT words INTO m FROM Temp0 LIMIT i, 1 ;
SET j = 1 ;
WHILE j <= m DO
INSERT INTO Temp1 SELECT words,id,api,basin,play,drilltype,tradeflag,score,cnf,fracdate,
fracdateend,state,county,operator,wellname,prodtype,latitude,
longitude,datum,depth,water,nonwater,surfactant,tradename,TRIM(Split_Str(tradename, ',', j)) AS tradename_c,
supplier,purpose,ingredients,cas,additive,fluid
FROM Temp0 LIMIT i,1 ;
SET j = j + 1 ;
END WHILE ;
SET i = i + 1 ;
END WHILE ;
RETURN '' ;
END ;
$$
The function gets progressively slower as the number of records increase.

Answer 1

If the question is "What is an example of an alternative way to do this same RBAR (row-by-agonizing-row) processing but which doesn't get progressively slower", I can give an example of what that would look like.
If there's an upper bound (maximum value) for words, this same result can be accomplished in a single statement:
INSERT INTO Temp1
( words, id, api, basin, play, drilltype, tradeflag ,score ,cnf, fracdate, fracdateend, state, county, operator, wellname, prodtype, latitude, longitude, datum, depth, water, nonwater, surfactant, tradename, supplier, purpose, ingredients, cas, additive, fluid
, tradename_c )
SELECT t.words,t.id,t.api,t.basin,t.play,t.drilltype,t.tradeflag,t.score,t.cnf,t.fracdate,t.fracdateend,t.state,t.county,t.operator,t.wellname,t.prodtype,t.latitude,t.longitude,t.datum,t.depth,t.water,t.nonwater,t.surfactant,t.tradename,t.supplier,t.purpose,t.ingredients,t.cas,t.additive,t.fluid
, TRIM(Split_Str(t.tradename, ',', n.i)) AS tradename_c
FROM Temp0 t
JOIN (SELECT 1 AS i UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9 UNION ALL SELECT 10 UNION ALL SELECT 11 UNION ALL SELECT 12 UNION ALL SELECT 13 UNION ALL SELECT 14 UNION ALL SELECT 15 UNION ALL SELECT 16 UNION ALL SELECT 17 UNION ALL SELECT 18 UNION ALL SELECT 19 UNION ALL SELECT 20) n
ON n.i <= t.words
But here is an example of a procedure that does the equivalent of the original procedure, except that it uses cursor loop instead of repeatedly re-querying the Temp0 table. Note that the datatypes of the variables (which accept the values from the row returned by fetch) should match or be compatible with the datatype of the corresponding expression in the SELECT list. Here I've declared them all as VARCHAR(100) as a placeholder, these will need to be changed to match the columns from the Temp0 table.
DELIMITER $$
CREATE FUNCTION RowPerRow_alt()
RETURNS VARCHAR(300)
BEGIN
-- variables for cursor fetch
-- the datatype of each variable should match the datatype
-- of the expression in SELECT list of the query
DECLARE v_words INT;
DECLARE v_id VARCHAR(100);
DECLARE v_api VARCHAR(100);
DECLARE v_basin VARCHAR(100);
DECLARE v_play VARCHAR(100);
DECLARE v_drilltype VARCHAR(100);
DECLARE v_tradeflag VARCHAR(100);
DECLARE v_score VARCHAR(100);
DECLARE v_cnf VARCHAR(100);
DECLARE v_fracdate VARCHAR(100);
DECLARE v_fracdateend VARCHAR(100);
DECLARE v_state VARCHAR(100);
DECLARE v_county VARCHAR(100);
DECLARE v_operator VARCHAR(100);
DECLARE v_wellname VARCHAR(100);
DECLARE v_prodtype VARCHAR(100);
DECLARE v_latitude VARCHAR(100);
DECLARE v_longitude VARCHAR(100);
DECLARE v_datum VARCHAR(100);
DECLARE v_depth VARCHAR(100);
DECLARE v_water VARCHAR(100);
DECLARE v_nonwater VARCHAR(100);
DECLARE v_surfactant VARCHAR(100);
DECLARE v_tradename VARCHAR(100);
DECLARE v_supplier VARCHAR(100);
DECLARE v_purpose VARCHAR(100);
DECLARE v_ingredients VARCHAR(100);
DECLARE v_cas VARCHAR(100);
DECLARE v_additive VARCHAR(100);
DECLARE v_fluid VARCHAR(100);
DECLARE j INT DEFAULT 0 ;
DECLARE v_tradename_c VARCHAR(100);
DECLARE done TINYINT(1) DEFAULT 0;
-- cursor for Temp0
DECLARE csr CURSOR FOR
SELECT words,id,api,basin,play,drilltype,tradeflag,score,cnf,fracdate,
fracdateend,state,county,operator,wellname,prodtype,latitude,
longitude,datum,depth,water,nonwater,surfactant,tradename,
supplier,purpose,ingredients,cas,additive,fluid
FROM Temp0;
-- setup NOT FOUND handler
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
OPEN csr;
rowloop: LOOP
FETCH csr INTO v_words,v_id,v_api,v_basin,v_play,v_drilltype,v_tradeflag,v_score,v_cnf,v_fracdate,v_fracdateend,v_state,v_county,v_operator,v_wellname,v_prodtype,v_latitude,v_longitude,v_datum,v_depth,v_water,v_nonwater,v_surfactant,v_tradename,v_supplier,v_purpose,v_ingredients,v_cas,v_additive,v_fluid;
IF done THEN
LEAVE rowloop;
END IF;
SET j = 1;
WHILE j <= v_words DO
-- split tradename and insert row ti Temp1
SET v_tradename_c = TRIM(Split_Str(v_tradename, ',', j));
INSERT INTO Temp1 ( words, id, api, basin, play, drilltype, tradeflag ,score ,cnf, fracdate, fracdateend, state, county, operator, wellname, prodtype, latitude, longitude, datum, depth, water, nonwater, surfactant, tradename, supplier, purpose, ingredients, cas, additive, fluid,
tradename_c )
VALUES ( v_words,v_id,v_api,v_basin,v_play,v_drilltype,v_tradeflag,v_score,v_cnf,v_fracdate,v_fracdateend,v_state,v_county,v_operator,v_wellname,v_prodtype,v_latitude,v_longitude,v_datum,v_depth,v_water,v_nonwater,v_surfactant,v_tradename,v_supplier,v_purpose,v_ingredients,v_cas,v_additive,v_fluid,
v_tradename_c );
SET j = j + 1 ;
END WHILE;
END LOOP rowloop;
CLOSE csr;
RETURN '' ;
END$$