how to improve performance of my query? - mysql

Question

we have written a query like below and also created proper indexes on table.
QUERY
SELECT ref_order_id, order_id, cams_ref_order_id
FROM cart_entries_archive
WHERE regular_price <> product_price
AND ref_order_id >0
AND cams_ref_order_id > 0;
But the query is performing full table scan due to this we are getting load spikes .
we tried by adding indexes on where clause columns but still performing full scan .Please rewrite the query if possible.
query explain plan
mysql> explain select ref_order_id,order_id,cams_ref_order_id from cart_entries_archive where regular_price <> product_price and ref_order_id >0 and cams_ref_order_id > 0;
+----+-------------+----------------------+------+---------------+------+---------+------+---------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+----------------------+------+---------------+------+---------+------+---------+-------------+
| 1 | SIMPLE | cart_entries_archive | ALL | NULL | NULL | NULL | NULL | 6490560 | Using where |
+----+-------------+----------------------+------+---------------+------+---------+------+---------+-------------+
1 row in set (0.00 sec)
Table structure:
mysql> show create table cart_entries_archive\G
*************************** 1. row ***************************
Table: cart_entries_archive
Create Table: CREATE TABLE `cart_entries_archive` (
`row_mod` datetime DEFAULT NULL,
`row_create` datetime DEFAULT NULL,
`address_id` int(11) DEFAULT NULL,
`backorder_date` datetime DEFAULT NULL,
`cancelled_date` datetime DEFAULT NULL,
`cart_entry_id` int(11) NOT NULL,
`cart_id` int(11) NOT NULL,
`delivery_date` datetime DEFAULT NULL,
`delivery_method` varchar(100) COLLATE latin1_bin DEFAULT NULL,
`delivery_note` varchar(255) COLLATE latin1_bin DEFAULT NULL,
`discount_amount` decimal(8,2) DEFAULT '0.00',
`gift_message` varchar(255) COLLATE latin1_bin DEFAULT NULL,
`occasion` varchar(255) COLLATE latin1_bin DEFAULT NULL,
`order_date` datetime DEFAULT NULL,
`order_id` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`order_status` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`product_name` varchar(255) COLLATE latin1_bin DEFAULT NULL,
`product_extra` varchar(255) COLLATE latin1_bin DEFAULT NULL,
`product_price` decimal(8,2) DEFAULT '0.00',
`product_count` int(11) DEFAULT NULL,
`product_cost` decimal(8,2) DEFAULT '0.00',
`product_sku` varchar(100) COLLATE latin1_bin DEFAULT NULL,
`product_notes` varchar(255) COLLATE latin1_bin DEFAULT NULL,
`parent_product_sku` varchar(100) COLLATE latin1_bin DEFAULT NULL,
`returned_date` datetime DEFAULT NULL,
`release_date` datetime DEFAULT NULL,
`regular_price` decimal(8,2) DEFAULT '0.00',
`shipping_cost` decimal(8,2) DEFAULT '0.00',
`service_charge` decimal(8,2) DEFAULT '0.00',
`sku_option_name` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`sku_option_value` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`shipping_company` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`shipping_fname` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`shipping_lname` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`shipping_address` varchar(100) COLLATE latin1_bin DEFAULT NULL,
`shipping_address2` varchar(100) COLLATE latin1_bin DEFAULT NULL,
`shipping_city` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`shipping_country` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`shipping_province` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`shipping_postal_code` varchar(10) COLLATE latin1_bin DEFAULT NULL,
`shipping_phone` varchar(20) COLLATE latin1_bin DEFAULT NULL,
`shipping_phone_ext` varchar(10) COLLATE latin1_bin DEFAULT NULL,
`ship_tracking_number` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`status` varchar(20) COLLATE latin1_bin DEFAULT NULL,
`tax` decimal(8,2) DEFAULT '0.00',
`total_charge` decimal(8,2) DEFAULT '0.00',
`website_id` int(11) DEFAULT NULL,
`microsite_id` int(11) DEFAULT NULL,
`defer_reason` varchar(255) COLLATE latin1_bin DEFAULT NULL,
`defer_key` varchar(255) COLLATE latin1_bin DEFAULT NULL,
`shipping_evening_phone` varchar(20) COLLATE latin1_bin DEFAULT NULL,
`shipping_mobile_phone` varchar(20) COLLATE latin1_bin DEFAULT NULL,
`shipping_email` varchar(100) COLLATE latin1_bin DEFAULT NULL,
`shipping_title` varchar(10) COLLATE latin1_bin DEFAULT NULL,
`shipping_district` varchar(30) COLLATE latin1_bin DEFAULT NULL,
`location_type` varchar(20) COLLATE latin1_bin DEFAULT NULL,
`occasion_id` int(11) DEFAULT NULL,
`occasion_date` datetime DEFAULT NULL,
`occasion_do_remind` int(11) DEFAULT NULL,
`coupon_ref_source_id` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`delivery_date_verified` int(11) DEFAULT NULL,
`florist_peak_charge` float DEFAULT NULL,
`member_id` varchar(10) COLLATE latin1_bin DEFAULT NULL,
`delivery_location_code` varchar(10) COLLATE latin1_bin DEFAULT NULL,
`simply_iflora` int(11) DEFAULT NULL,
`rotation_weight` int(11) DEFAULT NULL,
`area_charge` decimal(8,2) DEFAULT NULL,
`cf_indicator` varchar(5) COLLATE latin1_bin DEFAULT NULL,
`category_id` varchar(10) COLLATE latin1_bin DEFAULT NULL,
`cms_note` varchar(255) COLLATE latin1_bin DEFAULT NULL,
`qas_queried` int(11) DEFAULT NULL,
`shipping_verified` int(11) DEFAULT NULL,
`occasion_event_name` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`push_date` datetime DEFAULT NULL,
`ref_order_id` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`relationship` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`std_delivery_id` int(11) DEFAULT NULL,
`opt_delivery_id` int(11) DEFAULT NULL,
`service_date` datetime DEFAULT NULL,
`parameters` varchar(1024) COLLATE latin1_bin DEFAULT NULL,
`order_type` varchar(32) COLLATE latin1_bin DEFAULT NULL,
`cams_ref_order_id` varchar(50) COLLATE latin1_bin DEFAULT NULL,
`membership_discount` decimal(8,2) DEFAULT NULL,
PRIMARY KEY (`cart_entry_id`),
UNIQUE KEY `idx_2204` (`cart_entry_id`,`cart_id`),
UNIQUE KEY `idx_2318` (`cart_entry_id`,`order_id`),
KEY `idx_1049` (`order_date`),
KEY `idx_726` (`cart_id`),
KEY `idx_840` (`order_id`),
KEY `idx_row_create` (`row_create`),
KEY `idx_1035` (`push_date`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_bin
1 row in set (0.00 sec)

Answer 1

Your where clause uses ">" rather than "=", making it far less likely that an index will be useful. What % of rows in that table meet the criteria where ref_order_id>0 and cams_ref_order_id>0 ? If it is a high percentage, a table scan could be the fastest approach. Even if 10% of the records meet that criteria, it might mean the RDBMS has to read almost every page of the table.
If you want it to be "Index Only", you could add the following index:
create index TMP001 on cart_entries_archive
(ref_order_id, cams_ref_order_id, order_id, regular_price, product_price)
The fields from the where clause lead the index and everything else follows. If this is the only query you care about, and if the cost of maintaining the index is negligible, then create it and you're done.