Slow performance of combined MySQL queries - mysql

Question

I have this query with multiple subqueries which runs quite slow.
SELECT DISTINCT pav.products_options_values_id,
pav.products_options_values_name,
pav.products_options_values_sort_order
FROM products_stock ps,
products_options_values pav,
(
SELECT DISTINCT pa.products_id,
pov.products_options_values_id,
pov.products_options_values_name,
pa.options_values_price,
pa.price_prefix
FROM products_attributes pa,
products_options_values pov,
(
SELECT DISTINCT p.products_image,
p.products_quantity,
p.products_status,
m.manufacturers_id,
p.products_id,
p.products_date_added,
p.products_subimage1,
pd.products_name,
p.products_price,
p.products_length,
p.products_width,
p.products_height,
p.products_tax_class_id,IF(s.status, s.specials_new_products_price, NULL) AS specials_new_products_price,
IF(s.status, s.specials_new_products_price, p.products_price) AS final_price,
IF(p.clearance_price < p.products_cost*2.25, p.clearance_price, p.products_cost*2.25) AS sorting_price
FROM products p
LEFT JOIN manufacturers m
using (manufacturers_id)
LEFT JOIN specials s
ON p.products_id = s.products_id
LEFT JOIN products_attributes pa
ON p.products_id = pa.products_id
LEFT JOIN products_options po
ON pa.options_id = po.products_options_id
LEFT JOIN products_options_values pov
ON pa.options_values_id = pov.products_options_values_id ,
products_description pd,
categories c,
products_to_categories p2c
WHERE p.products_status = '1'
AND p.products_id = pd.products_id
AND pd.language_id = '1'
AND p.products_id = p2c.products_id
AND p2c.categories_id = c.categories_id
AND ((
pd.products_name LIKE '%a%'
OR po.products_options_name LIKE '%a%'
OR pov.products_options_values_name LIKE '%a%'
OR pd.products_description LIKE '%a%') )
ORDER BY p.products_id DESC) m
WHERE m.products_id = pa.products_id
AND pa.options_id = 1
AND pa.options_values_id = pov.products_options_values_id
AND pov.language_id = '1'
GROUP BY pov.products_options_values_id
ORDER BY pov.products_options_values_sort_order ASC) q
WHERE q.products_id = ps.products_id
AND ps.products_stock_attributes = concat('1-', pav.products_options_values_id)
AND ps.products_stock_quantity > 0
ORDER BY pav.products_options_values_sort_order ASC
This is EXPLAIN result:
Been trying to optimize it for hours, but I probably misread the EXPLAIN information because no matter what I do, it doesn't seem to make it faster, so I am reaching out for help from the experts here.
What can be the cause of it becoming so slow and what should I do to make it fast?

Answer 1

First, I cleaned up the query using consistent JOIN clauses vs comma listed tables. Next, your inner-most query has an order by which apparently is not being utilized to any benefit. Order by will typically cause big delay in queries if it cant be optimized.
SELECT DISTINCT
pav.products_options_values_id,
pav.products_options_values_name,
pav.products_options_values_sort_order
FROM
products_stock ps
JOIN products_options_values pav
ON ps.products_stock_attributes = concat('1-', pav.products_options_values_id)
AND ps.products_stock_quantity > 0
JOIN ( SELECT DISTINCT
pa.products_id,
pov.products_options_values_id,
pov.products_options_values_name,
pa.options_values_price,
pa.price_prefix
FROM
products_attributes pa
JOIN products_options_values pov
ON pa.options_values_id = pov.products_options_values_id
AND pov.language_id = '1'
JOIN ( SELECT DISTINCT
p.products_image,
p.products_quantity,
p.products_status,
p.manufacturers_id,
p.products_id,
p.products_date_added,
p.products_subimage1,
pd.products_name,
p.products_price,
p.products_length,
p.products_width,
p.products_height,
p.products_tax_class_id,
IF(s.status, s.specials_new_products_price, NULL )
AS specials_new_products_price,
IF(s.status, s.specials_new_products_price, p.products_price )
AS final_price,
IF( p.clearance_price < p.products_cost * 2.25, p.clearance_price, p.products_cost * 2.25 )
AS sorting_price
FROM
products p
JOIN products_description pd
ON p.products_id = pd.products_id
AND pd.language_id = '1'
THIS SECTION CAN BE REMOVED JOIN products_to_categories p2c
AND p.products_id = p2c.products_id
JOIN categories c
ON p2c.categories_id = c.categories_id
LEFT JOIN manufacturers m
UP TO THIS LINE ON P.manufacturers_id = m.manufacturers_id
LEFT JOIN specials s
ON p.products_id = s.products_id
LEFT JOIN products_attributes pa
ON p.products_id = pa.products_id
LEFT JOIN products_options po
ON pa.options_id = po.products_options_id
LEFT JOIN products_options_values pov
ON pa.options_values_id = pov.products_options_values_id,
WHERE
p.products_status = '1'
AND ( pd.products_name LIKE '%a%'
OR pd.products_description LIKE '%a%'
OR po.products_options_name LIKE '%a%'
OR pov.products_options_values_name LIKE '%a%' )
ORDER BY
p.products_id DESC) m
WHERE
pa.products_id = m.products_id
AND pa.options_id = 1
GROUP BY
pov.products_options_values_id
ORDER BY
pov.products_options_values_sort_order ASC) q
ON ps.products_id = q.products_id
ORDER BY
pav.products_options_values_sort_order ASC
You have a join to your categories table, but not pulling any values or other criteria to return columns. I have thus removed as it is unnecessary. WITH that gone, I then looked at your Products_To_Categories table AND that too has no bearing in the query other than an extra join not being used anywhere else and thus removed. The Manufacturers table is also not required as all you are getting is the manufacturer's ID, which exists on the products table, so yet ANOTHER table not required
Now on to indexes. I would look at the following indexes for your tables
table index
products ( products_status, products_id )
products_description ( products_id, language_id )
products_to_categories ( products_id, categories_id )
categories ( categories_id )
manufacturers ( manufacturers_id )
specials ( products_id, status, specials_new_products_price )
products_attributes ( products_id, options_id, options_values_id )
products_options ( products_options_id, products_options_name )
products_options_values ( products_options_values_id, products_options_values_name )
This is just a first pass at the review. Now I want to take it one additional step to possibly remove a layer of nested queries. Your INNER-MOST query does a join to "products_options_values" but ONLY for Language ID = 1. Why would you not add that column criteria to the inner query. Then add the pov.products_options_values_id and pov.products_options_values_name columns to your inner query and language ID to the inner query and you don't need to re-join to them again. They can be referenced via the "m." alias of the inner-most query. vs the rejoin.
Similarly, your inner-most query does a LEFT JOIN to the products_attributes, but outside the "m" alias query result applies a WHERE clause ONLY of options_id = 1. This doesn't make sense. Why not just add that too to the inner-most query. Eliminate the extra levels would probably help a lot as you are limiting down a pull of all records if you are only looking for things like Language ID = 1, or Options_ID = 1.
Again, this formatted query IS the same context as yours, just structured slightly different and shorter indentation to see better the context and nested requirements.
FEEDBACK FROM CHAT
select
PQ.*
from
( SELECT STRAIGHT_JOIN DISTINCT
p.products_id,
p.products_image,
p.products_quantity,
p.products_status,
p.manufacturers_id,
p.products_date_added,
p.products_subimage1,
pd.products_name,
p.products_price,
p.products_length,
p.products_width,
p.products_height,
pov.products_options_values_id,
pov.products_options_values_name,
pov.language_id,
pov.products_options_values_sort_order,
p.products_tax_class_id,
IF(s.status, s.specials_new_products_price, NULL)
AS specials_new_products_price,
IF(s.status, s.specials_new_products_price, p.products_price)
AS final_price,
IF(p.clearance_price < p.products_cost*2.25, p.clearance_price, p.products_cost*2.25)
AS sorting_price
FROM
products_attributes pa
JOIN products_options_values pov
ON pa.options_values_id = pov.products_options_values_id
AND pov.language_id = '1'
LEFT JOIN products_options po
ON pa.options_id = po.products_options_id
JOIN products p
ON pa.products_id = p.products_id
AND p.products_status = '1'
JOIN products_description pd
ON p.products_id = pd.products_id
AND pd.language_id = '1'
JOIN products_to_categories p2c
ON p.products_id = p2c.products_id
JOIN categories c
ON p2c.categories_id = c.categories_id
LEFT JOIN manufacturers m
using (manufacturers_id)
LEFT JOIN specials s
ON p.products_id = s.products_id
WHERE
pa.options_id = '1'
AND ( pd.products_name LIKE '%a%'
OR po.products_options_name LIKE '%a%'
OR pov.products_options_values_name LIKE '%a%'
OR pd.products_description LIKE '%a%')) PQ
order by
PQ.Products_id
Also, note, I removed the final "Order by" clause