Thread: How to write UDF in C that resemble the LIKE function

b t <qtboyzz@yahoo.com> writes:
> I have a question, as part of the project that I have to do for
> school, we have to implement a User Define Function in C that is
> similar like the LIKE funtion in PostgreSQL. For example where a
> customer is searching for an actor whose last name sounds like
> "Schwarseneger" (notice the typo). However, the customer is not sure
> neither about the spelling nor the pronunciation. The real star name
> should be "Schwarzenegger". In this case, the "LIKE" operator in SQL
> is not capable enough. It would be nice if the search would match last
> names "similar to" "Schwarseneger". Can Some one please give me some
> pointer on this or even sample code that you might have
> implemented. So basically the thing that I'm doing is like a spell
> check system where it return the closest match to the word.

Didn't your professor notice that there are two or three of those
already in contrib/fuzzystrmatch?
        regards, tom lane

On Sat, Feb 12, 2005 at 07:40:17PM -0800, b t wrote:
>  
> I have a question, as part of the project that I have to do for school,
> we have to implement a User Define Function in C that is similar like the
> LIKE funtion in PostgreSQL. For example where a customer is searching for
> an actor whose last name sounds like "Schwarseneger" (notice the typo).
> However, the customer is not sure neither about the spelling nor the
> pronunciation. The real star name should be "Schwarzenegger".

The contrib/fuzzystrmatch module contains implementations of the
soundex, levenshtein, and metaphone algorithms.  Here's an example:

CREATE TABLE actor (   id    serial PRIMARY KEY,   name  text NOT NULL
);

INSERT INTO actor (name) VALUES ('Schwarzenegger');

SELECT * FROM actor WHERE soundex(name) = soundex('Schwarseneger');id |      name      
----+---------------- 1 | Schwarzenegger

You could create a functional index to speed up queries on large
tables:

CREATE INDEX actor_name_soundex_idx ON actor (soundex(name));

-- 
Michael Fuhr
http://www.fuhr.org/~mfuhr/