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All the Perl that's Practical to Extract and Report

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  • How fast is

    SELECT authname FROM invoices i WHERE i.affid = 654248 AND i.commpaid = 0;

    You're doing a full table scan on invoices alone, without the join, and that SHOULD be painful.

    So, index on affid.

    • Bingo! That reduces the query time down to .15 seconds :)

      I don't understand the EXPLAIN output as well as I should (duh!). How did you deduce the full table scan on invoice from this?

      +----+-------------+-------+--------+------------------+----------+---------+--- -------------+---------+-------------+
      | id | select_type | table | type   | possible_keys    | key      | key_len | ref            | rows    | Extra   

      • Well, it is not really a full table scan but it is close to this. Explain select says that it needs to scan 1879054 rows out of 3770990. Concerning performance it is pretty much equivalent to the full table scan. Actually if lookup on an index returns ~50% or more of your table it could be even slower that the full table scan.
        --

        Ilya Martynov (http://martynov.org/ [martynov.org])