Currently using View, Should I use a hard table instead? - mysql

Question

I am currently debating whether my table, mapping_uGroups_uProducts, which is a view formed by the following table:
CREATE ALGORITHM=UNDEFINED DEFINER=`root`#`localhost`
SQL SECURITY DEFINER VIEW `db`.`mapping_uGroups_uProducts`
AS select distinct `X`.`upID` AS `upID`,`Z`.`ugID` AS `ugID` from
((`db`.`mapping_uProducts_Products` `X` join `db`.`productsInfo` `Y`
on((`X`.`pID` = `Y`.`pID`))) join `db`.`mapping_uGroups_Groups` `Z`
on((`Y`.`gID` = `Z`.`gID`)));
My current query is:
SELECT upID FROM uProductsInfo \
JOIN fs_uProducts USING (upID) column \
JOIN mapping_uGroups_uProducts USING (upID) -- could be faster if we use hard table and index \
JOIN mapping_fs_key USING (fsKeyID) \
WHERE fsName="OVERALL" \
AND ugID=1 \
ORDER BY score DESC \
LIMIT 0,30;
which is pretty slow. (for 30 results, it requires about 10 secondes). I think the reason for my query being so slow is definitely due to the fact that that particular query relies on a VIEW which has no index to speed things up.
+----+-------------+----------------+--------+----------------+---------+---------+---------------------------------------+-------+---------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+----------------+--------+----------------+---------+---------+---------------------------------------+-------+---------------------------------+
| 1 | PRIMARY | mapping_fs_key | const | PRIMARY,fsName | fsName | 386 | const | 1 | Using temporary; Using filesort |
| 1 | PRIMARY | <derived2> | ALL | NULL | NULL | NULL | NULL | 19706 | Using where |
| 1 | PRIMARY | uProductsInfo | eq_ref | PRIMARY | PRIMARY | 4 | mapping_uGroups_uProducts.upID | 1 | Using index |
| 1 | PRIMARY | fs_uProducts | ref | upID | upID | 4 | db.uProductsInfo.upID | 221 | Using where |
| 2 | DERIVED | X | ALL | PRIMARY | NULL | NULL | NULL | 40772 | Using temporary |
| 2 | DERIVED | Y | eq_ref | PRIMARY | PRIMARY | 4 | db.X.pID | 1 | Distinct |
| 2 | DERIVED | Z | ref | PRIMARY | PRIMARY | 4 | db.Y.gID | 2 | Using index; Distinct |
+----+-------------+----------------+--------+----------------+---------+---------+---------------------------------------+-------+---------------------------------+
7 rows in set (0.48 sec)
The explain here looks pretty cryptic, and I don't know whether I should drop view and write a script to just insert everything in the view to a hard table. ( obviously, it will lose the flexibility of the view since the mapping changes quite frequently).
Does anyone have any idea to how I can optimize my schema better?

Answer 1

You current plan uses the view as a driven table: it is scanned for each record in mapping_fs_key with fsName = 'OVERALL'
You could replace the view with this function:
SELECT upID FROM uProductsInfo
JOIN fs_uProducts USING (upID)
JOIN mapping_fs_key USING (fsKeyID)
WHERE fsName='OVERALL'
AND upID IN
(
SELECT upID
FROM mapping_uGroups_Groups Z
JOIN productsInfo Y
ON y.gID = z.gID
JOIN mapping_uProducts_Products X
ON x.pID = y.pID
WHERE z.ugID = 1
)
ORDER BY
score DESC
LIMIT 0,30