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Re: perl script performs poorly - please advise
Posted by: Rick James
Date: April 11, 2009 09:37PM

A rule of thumb: If you are looping through the output of one SELECT in order to do a bunch of other statements (DELETEs, UPDATEs, in your case), you are not using the power of SQL. It should be possible to your two snippets in two statements.

Does never2 have just one column? Consider this:
CREATE TABLE new_never 
    SELECT DISTINCT email FROM never2;
RENAME TABLE never2 TO old_never,
             new_never TO never2;
DROP TABLE old_never; 
ALTER TABLE never2
    ADD PRIMARY KEY(email);
Ok, that's 3 statements. But muuuuuch faster.

The other one would involve a multi-table update:
http://dev.mysql.com/doc/refman/5.0/en/update.html
(and should take only one command)

BTW, there needs to be an index on email for the never2 table.

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Re: perl script performs poorly - please advise
April 11, 2009 09:37PM


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