Query result is very slow - mysql

Question

I am developing a website like any other social networking site using mysql.
I wish it give people suggestion to my users, and I have implemented this functionality in my application, but It is working very slow. this process take 2-3 seconds to fetch result from server. It has all the necessary indexes, relations on table. I have used EXPLAIN command to understand it, but I got nothing problematic in it.
I can't understand what is the basic problem in it. Please help me.
here is my table structure :
Table : UserMaster
~~~~~~~~~~~~~~~~~~
CREATE TABLE `UserMaster` (
`UserID` mediumint(8) unsigned NOT NULL AUTO_INCREMENT,
`UserName` varchar(20) DEFAULT NULL,
`EMailID` varchar(50) DEFAULT NULL,
`FirstName` varchar(20) NOT NULL,
`LastName` varchar(20) NOT NULL,
`CityID` mediumint(8) unsigned DEFAULT NULL,
PRIMARY KEY (`UserID`),
UNIQUE KEY `UX_UserMaster_UserName` (`UserName`),
UNIQUE KEY `UX_UserMaster_EMailID` (`EMailID`),
KEY `FK_UserMaster_CityMst_CityID_idx` (`CityID`),
KEY `FK_UserMaster_CountryMst_CountryID_idx` (`CountryID`),
CONSTRAINT `FK_UserMaster_CityMst_CityID`
FOREIGN KEY (`CityID`) REFERENCES `CityMst` (`CityID`) ON DELETE NO ACTION,
CONSTRAINT `FK_UserMaster_CountryMst_CountryID` FOREIGN KEY CountryID REFERENCES CountryMst (CountryID) ON DELETE NO ACTION ON UPDATE CASCADE
)
ENGINE=InnoDB AUTO_INCREMENT=19722 DEFAULT CHARSET=utf8$$
Table : UserFriends
~~~~~~~~~~~~~~~~~~~
CREATE TABLE `UserFriends` (
`FriendID` mediumint(8) unsigned NOT NULL AUTO_INCREMENT,
`UserID` mediumint(8) unsigned NOT NULL,
`UserID2` mediumint(8) unsigned NOT NULL,
`RequestDate` timestamp NULL DEFAULT CURRENT_TIMESTAMP,
`Status` tinyint(3) unsigned NOT NULL DEFAULT '2',
`ApprovalDate` timestamp NULL DEFAULT NULL,
PRIMARY KEY (`FriendID`),
UNIQUE KEY `UX_UserFriends_UserID_UserID2` (`UserID`,`UserID2`),
KEY `IX_UserFriens_UserID_ApprovalStatus` (`UserID`,`ApprovalStatus`,`UserID2`,`FriendID`,`RequestDate`,`ApprovalDate`),
KEY `FK_UserFriends_UserMaster_UserID_idx` (`UserID`),
KEY `FK_UserFriends_UserMaster_UserID2_idx` (`UserID2`),
CONSTRAINT `FK_UserFriends_UserMaster_UserID` FOREIGN KEY (`UserID`) REFERENCES `UserMaster` (`UserID`) ON DELETE NO ACTION ON UPDATE CASCADE,
CONSTRAINT `FK_UserFriends_UserMaster_UserID2` FOREIGN KEY (`UserID2`) REFERENCES `UserMaster` (`UserID`) ON DELETE NO ACTION ON UPDATE CASCADE
)
ENGINE=InnoDB AUTO_INCREMENT=50825 DEFAULT CHARSET=utf8$$
UserID & UserID2 both fields are linked with UserMaster.UserID
Here is my select query :
~~~~~~~~~~~~~~~~~~~~~~~~~
SELECT
upm.UserID,
upm.UserName,
upm.FirstName,
COALESCE(mf.TotMutualFriends,0) TotMutualFriends
FROM UserMaster upm
LEFT JOIN CityMst ct on ct.CityID = upm.CityID
LEFT JOIN StateMst st on st.StateID = ct.StateID
LEFT JOIN (
SELECT uf.UserID, COUNT(1) TotMutualFriends
FROM (
SELECT uf.UserID, uf.UserID2, uf.ApprovalStatus
FROM UserFriends uf
UNION ALL
SELECT uf.UserID2 UserID, uf.UserID UserID2, uf.ApprovalStatus
FROM UserFriends uf
) uf
INNER JOIN (
SELECT IF(uf.UserID = 1, uf.UserID2, uf.UserID) UserID2
FROM UserFriends uf
WHERE (uf.UserID = 1 OR uf.UserID2 = 1)
AND uf.ApprovalStatus = 1
) uf1 on uf1.UserID2 = uf.UserID2
WHERE uf.ApprovalStatus = 1
GROUP BY uf.UserID
) mf on mf.UserID = upm.UserID
LEFT JOIN (
SELECT DISTINCT usar.UserID2
FROM UserSuggAutoRejct usar
WHERE usar.UserID = 1
UNION
SELECT IF(uf.UserID = 1, uf.UserID2, uf.UserID) UserID2
FROM UserFriends uf
WHERE (uf.UserID = 1 OR uf.UserID2 = 1)
) usar ON usar.UserID2 = upm.UserID
WHERE upm.UserStatus IN(10,11)
AND upm.UserID <> 1
AND upm.UserID NOT IN (1221,2191)
AND usar.UserID2 IS NULL
ORDER BY
(CASE WHEN COALESCE(mf.TotMutualFriends,0) > 0 THEN 0 ELSE 1 END),
(CASE WHEN COALESCE(mf.TotMutualFriends,0) > 0 THEN RAND() ELSE NULL END),
(CASE upm.CityID WHEN 1 THEN 0 ELSE 1 END),
(CASE upm.CityID WHEN 1 THEN RAND() ELSE NULL END),
(CASE ct.StateID WHEN 1 THEN 0 ELSE 1 END),
(CASE ct.StateID WHEN 1 THEN RAND() ELSE NULL END),
(CASE st.CountryID WHEN 91 THEN 0 ELSE 1 END),
(CASE st.CountryID WHEN 91 THEN RAND() ELSE NULL END)
LIMIT 10
This is performing very slow. It takes 2-3 seconds to evolute.

Answer 1

relational database might not be relevant for social networking sites.
because joining table is very slow, try using other no-sql databases(NoSql type database).
if u still insist using mysql, then try not to much join in your query.
sorry for my bad english, if any.