How score() function works in HANA fuzzy search

Question

Hi, i am confused by the score() returned value when i use this in fuzzy search in HANA
CREATE COLUMN TABLE test_similar_calculation_mode
( id INTEGER PRIMARY KEY, s text);
INSERT INTO test_similar_calculation_mode VALUES ('1','stringg');
INSERT INTO test_similar_calculation_mode VALUES ('2','string theory');
INSERT INTO test_similar_calculation_mode VALUES ('3','this is a very very very long string');
INSERT INTO test_similar_calculation_mode VALUES ('4','this is another very long string');
SELECT TO_INT(SCORE()*100)/100 AS score, id, s FROM test_similar_calculation_mode WHERE CONTAINS(s, 'theory', FUZZY(0.9, 'similarCalculationMode=compare')) ORDER BY score DESC;
the returned list is just as below
SCORE      ID      S
0.84            2       string theory
why i assign 0.9 as threshold in fuzzy function while this line with score 0.84 also be returned.
from my understanding, the S field is text data type, so the string actually is divided into seperate word list, so the score should be 1.0, is it right?
any hints is very appreciate,thanks

Answer 1

Hi William,
By default the score() function returns a TF/IDF score for text data types.
To get back the fuzzy score, you have to use the search option 'textSearch=compare' (or 'ts=compare'). Without other options, this gives an average score of all tokens ('string' and 'theory') and you get a score of 0.7 as a result.
To ignore the additional token 'string' in the database, you have to specify another option that tells the score function to use the tokens from the user input only ('cnmt=input').
So you should use
TO_INT(SCORE()*100)/100 AS score, id, s
FROM test_similar_calculation_mode
WHERE CONTAINS(s, 'theory', FUZZY(0.9, 'scm=compare, ts=compare, cnmt=input'))
ORDER BY score DESC;
to get the expected results.
Regards,
Jörg