How To Apply Indexing this Query - php

Question

SELECT user_id,username,full_name,display_name,profile_pic,email,
fb_id,image1,image2,image3,image4,image5,default_pic,
street_address,locality,country,state,is_verified,is_online,
city,image6,image7,image8,image9,image10,last_login,
IFNULL( (
SELECT STATUS
FROM vidioo_contacts
WHERE (contact_id = '55000'
AND user_id = vu.user_id
)
OR (contact_id = vu.user_id
AND user_id = '55000')),0) AS STATUS,
(3959 * ACOS( COS(RADIANS(0)) * COS(RADIANS(latitude)) *
COS(RADIANS(longitude) - RADIANS(0)) + SIN(RADIANS(0)) *
SIN(RADIANS(latitude)))
) AS distance
FROM vidioo_users vu
WHERE user_id != '55000'
AND gender LIKE
( SELECT CASE WHEN show_me = 'everyone'
THEN '%'
ELSE IF(LENGTH(show_me) < 1, '%', show_me)
END
FROM vidioo_users
WHERE user_id = '55000'
LIMIT 1
)
AND IFNULL(vu.is_deleted,0) != 55000
AND vu.user_id NOT IN (
SELECT DISTINCT contact_id
FROM vidioo_blocked_users
WHERE bloked_by_user = 55000
)
AND DATEDIFF(NOW(),last_login) < 7
ORDER BY last_login DESC
LIMIT 0,20
I wish to apply indexing to this query.

Answer 1

If the table has a multiple-column index then mysql uses leftmost prefix of the index. For example you have following select queries -
`SELECT * FROM tbl_name WHERE col1=val1;
SELECT * FROM tbl_name WHERE col1=val1 AND col2=val2;
SELECT * FROM tbl_name WHERE col2=val2;
SELECT * FROM tbl_name WHERE col2=val2 AND col3=val3;`
If an index exists on (col1, col2, col3), only the first two queries use the index. The third and fourth queries do involve indexed columns, but (col2) and (col2, col3) are not leftmost prefixes of (col1, col2, col3).
In your case you must have to create 3 indexes as
Index_1(user_id, gender, last_login)
Index_2(user_id)
Index_3(bloked_by_user)
NOTE:- Too many indexing slow down INSERT query processing.
For more details Click here

Answer 2

In addition to the other suggestions, change AND DATEDIFF(NOW(),last_login) < 7 to
last_login > NOW() - INTERVAL 7 DAY
What you have hides the column last_login inside a function (DATEDIFF), making it unusable with indexing. Then, also, add
INDEX(last_login)
(It may not help, but it may.)
Also, change
AND vu.user_id NOT IN (
SELECT DISTINCT contact_id
FROM vidioo_blocked_users
WHERE bloked_by_user = 55000
)
to
AND NOT EXISTS( SELECT * FROM vidioo_blocked_users
WHERE bloked_by_user = 55000
AND contact_id = vu.user_id )
Together with
INDEX(bloked_by_user, contact_id) -- in either order

Answer 3

Try adding indexes on these four table columns, It should help:
contact_id,
user_id,
is_deleted,
last_login.