Mysql Slow Query Optimization

Question

I have a shopping cart that continually logs slow queries like this one...

# Query_time: 4  Lock_time: 0  Rows_sent: 50  Rows_examined: 454403
    SELECT SQL_CALC_FOUND_ROWS products.*, 
                           descr1.product                          AS product, 
                           Min(prices.price)                       AS price, 
                           GROUP_CONCAT(IF(products_categories.link_type = 'M', 
                           Concat(products_categories.category_id, 
                           'M'), products_categories.category_id)) AS 
                           category_ids, 
                           cscart_seo_names.name                   AS seo_name 
FROM   cscart_products AS products 
       LEFT JOIN cscart_product_descriptions AS descr1 
         ON descr1.product_id = products.product_id 
            AND descr1.lang_code = 'EN' 
       LEFT JOIN cscart_product_prices AS prices 
         ON prices.product_id = products.product_id 
            AND prices.lower_limit = 1 
       INNER JOIN cscart_products_categories AS products_categories 
         ON products_categories.product_id = products.product_id 
       INNER JOIN cscart_categories 
         ON cscart_categories.category_id = products_categories.category_id 
            AND ( cscart_categories.usergroup_ids = '' 
                   OR Find_in_set(0, cscart_categories.usergroup_ids) 
                   OR Find_in_set(1, cscart_categories.usergroup_ids) ) 
            AND cscart_categories.status IN ( 'A', 'H' ) 
       LEFT JOIN cscart_seo_names 
         ON cscart_seo_names.object_id = products.product_id 
            AND cscart_seo_names.TYPE = 'p' 
            AND cscart_seo_names.dispatch = '' 
            AND cscart_seo_names.lang_code = 'EN' 
WHERE  1 
       AND products.company_id = 0 
       AND ( products.usergroup_ids = '' 
              OR Find_in_set(0, products.usergroup_ids) 
              OR Find_in_set(1, products.usergroup_ids) ) 
       AND products.status IN ( 'A' ) 
       AND prices.usergroup_id IN ( 0, 0, 1 ) 
GROUP  BY products.product_id 
ORDER  BY descr1.product ASC 
LIMIT  1300, 50;

I can't seem to get any help from the cart company on how to speed this query up. Maybe I need to add more indexes? I am not sure and would love to get some help that would point me in t right direction to solving this problem.

Thanks,

Chris Edwards

EXPLAIN is your best friend

meze
– meze

2011-10-12 16:37:04 +00:00
Commented Oct 12, 2011 at 16:37 — meze
– meze, Commented Oct 12, 2011 at 16:37

Seth · Accepted Answer · 2011-10-12 16:41:08Z

1

I see a lot of issues with this query that could be causing slowness...

First of all, anywhere you are using 'FIND_IN_SET', try using IN instead. By removing the 'OR' in the conditions, indexes can be used:

cscart_categories.usergroup_ids = ''
OR FIND_IN_SET(0, cscart_categories.usergroup_ids)
OR FIND_IN_SET(1, cscart_categories.usergroup_ids)

Becomes:

cscart_categories.usergroup_ids IN ('', '0', '1')

Other than that, make sure that every column that is being used in a join, group by clause, where clause, or ordering is indexed.

Another suggestion would be to remove the 'GROUP_CONCAT' and select that information separately in another query.

answered Oct 12, 2011 at 16:41

Seth

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1 Comment

Seth Over a year ago

You're right about the first part not working...the IN function will not work instead of the FIND_IN_SET function. The only other way to optimize this that I know of would be to remove the OR conditions and use UNIONS instead for each where condition.

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