Re: Fuzzy substring searching with the pg_trgm extension

>>> The behavior of this function is surprising to me.
>>>
>>> select substring_similarity('dog' ,  'hotdogpound') ;
>>>
>>>   substring_similarity
>>> ----------------------
>>>                   0.25
>>>
>> Substring search was desined to search similar word in string:
>> contrib_regression=# select substring_similarity('dog' ,  'hot dogpound') ;
>>   substring_similarity
>> ----------------------
>>                   0.75
>>
>> contrib_regression=# select substring_similarity('dog' ,  'hot dog pound') ;
>>   substring_similarity
>> ----------------------
>>                      1
>
> Hmm, this behavior looks too much like magic to me.  I mean, a substring
> is a substring -- why are we treating the space as a special character
> here?

Because  it isn't a regex for substring search. Since implementing, pg_trgm 
works over words in string.
contrib_regression=# select similarity('block hole', 'hole black'); similarity
------------   0.571429
contrib_regression=# select similarity('block hole', 'black     hole'); similarity
------------   0.571429

It ignores spaces between words and word's order.

I agree, that substring_similarity is confusing name, but actually it search 
most similar word in second arg to first arg and returns their similarity.


-- 
Teodor Sigaev                                   E-mail: teodor@sigaev.ru
  WWW: http://www.sigaev.ru/