减少查询的执行时间

Question

I want to reduce the time taken by the query in mysql.

There are three tables say

1. A ~600k rows,
2. B ~2K rows,
3. C ~100K rows

having 2 columns each.

1. A has one column which is used in aggregation and other to join with table B.
2. B has one column to join with A and other with C
3. C has one column to join with B and other column to group by.

What should be the indexing plan to reduce the run time. As of now it is using temporary tables and then file sort. Is there any way we could avoid temporary tables.

Sample query :

 SELECT
      sum(`revenue_facts`.`total_price`) AS `m0`
FROM 
    `category_groups` AS `category_groups`,
    `revenue_facts` AS `revenue_facts`,
    `dim_products` AS `dim_products`
WHERE 
    `dim_products`.`product_category_group_sk` =       `category_groups`.`product_category_group_sk` AND  
    `revenue_facts`.`product_sk` = `dim_products`.`product_sk`
GROUP BY `category_groups`.`category_name`;

I already have indexes on group by column and the columns in join.

my query is currently taking * 6 minute *s. I want to reduce the time taken. table structure is as

table A :

CREATE TABLE `revenue_facts` (
  `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
  `product_sk` bigint(20) unsigned NOT NULL,
  `total_price` decimal(12,2) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `product_sk` (`product_sk`),
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Table B :

CREATE TABLE `dim_products` (
  `product_sk` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
  `product_category_group_sk` bigint(20) unsigned NOT NULL,
  PRIMARY KEY (`product_sk`),
  KEY `product_id` (`product_id`),
 KEY (`product_sk`) (`product_sk`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8;

table C :

CREATE TABLE `category_groups` (
  `product_category_group_sk` bigint(20) unsigned NOT NULL,
  `category_sk` bigint(20) unsigned NOT NULL,
  `category_name` varchar(255) NOT NULL,
  PRIMARY KEY (`product_category_group_sk`,`category_sk`),
  KEY `category_sk` (`category_sk`),
  KEY `product_category_group_sk` (`product_category_group_sk`
  KEY `category_sk` (`category_name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Execution plan used is:

1   SIMPLE  dim_products    index   PRIMARY,product_category_group_index    product_category_group_index    8   NULL    651264  Using index; Using temporary; Using filesort
1   SIMPLE  category_groups ref PRIMARY,category_sk,product_category_group_sk,category_name product_category_group_sk   8 etl_testing.dim_products.product_category_group_sk    4   Using index
1   SIMPLE  revenue_facts   ref product_sk  product_sk  8 etl_testing..dim_products.product_sk  5   NULL

Answer 1

Try this:

SELECT
    sum(`revenue_facts`.`total_price`) AS `m0`
FROM 
    (`dim_products` LEFT JOIN `category_groups` ON `dim_products`.`product_category_group_sk` =  `category_groups`.`product_category_group_sk`)
    LEFT JOIN `revenue_facts` ON `dim_products`.`product_sk` = `revenue_facts`.`product_sk`
GROUP BY `category_groups`.`category_name`;

Also, as Abdul said:

"Post your table structures and explain plan"