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Re: query optimization
Posted by: Rick James
Date: March 13, 2010 09:11AM

Do you need the COUNT, or simply "there is at least one"?
It may not help a lot, but you could eliminate some of the stopwords thus:

# Need to declare stopword VARBINARY(...) -- this will allow the inequalities below to work correctly.
# Plus, have an index (probably PRIMARY KEY) on stopword.

# First use the regexps that start with the same letter as 'test':
SELECT 1 FROM stopwords
   WHERE stopword LIKE CONCAT('^', LEFT('test', 1), '%')
     AND 'test' REGEXP stopword
   LIMIT 1;
# if you get 1 (as opposed to no rows) from that, exit with "got a stopword".

# else test harder:
SELECT 1 FROM stopwords
   WHERE stopword < 'A'
     AND 'test' REGEXP stopword
   LIMIT 1;
# that will cover leading '.' '(' (etc)
# exit if get 1.

SELECT 1 FROM stopwords
   WHERE stopword > 'Z' and stopword < 'a'
     AND 'test' REGEXP stopword
   LIMIT 1;
# that will cover leading '[' '\' (etc)

If you have a lot of stopwords beginning with .* this approach will need rethinking.

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