MySQL first free number between exists values - mysql

Question

Problem: Get first free port for server between exists values. If there is not a free place then take the highest + 1.
Extra: If server_deleted=1 then we can take the free port. Also we should take the free port when there is a gap between values. We should include server_type in where clause. The min value is first port e.g. 9000.
Now my query looks:
SELECT server_port + 1
FROM pro_servers s
WHERE s.server_port <> 0
AND s.server_type = 'ts3'
AND s.server_deleted = 0
AND NOT EXISTS
( SELECT s1.server_port
FROM pro_servers s1
WHERE s1.server_port <> 0
AND s1.server_type = 'ts3'
AND s1.server_port = s.server_port + 1
AND s1.server_deleted = 0
)
ORDER BY server_port LIMIT 1
I think there is better way to do it. This query executes very slow.
For example the first=minimum=lowest = 9000, next is 9002, 9003. We need to get the 9001. If we add 9001 then get 9004. The first value 9000 exists in the table.
SAMPLE DATA
+-----------+-------------+----------------+-------------+
| server_id | server_port | server_deleted | server_type |
+-----------+-------------+----------------+-------------+
| 151 | 9500 | 1 | teamspeak3 |
| 8459 | 9500 | 0 | teamspeak3 |
| 183 | 9501 | 1 | teamspeak3 |
| 264 | 9502 | 1 | teamspeak3 |
| 4155 | 9502 | 1 | teamspeak3 |
| 2707 | 9503 | 1 | teamspeak3 |
| 4160 | 9503 | 1 | teamspeak3 |
| 154 | 9504 | 1 | teamspeak3 |
| 4163 | 9504 | 1 | teamspeak3 |
| 285 | 9506 | 1 | teamspeak3 |
| 4167 | 9506 | 1 | teamspeak3 |
| 8454 | 9506 | 0 | teamspeak3 |
| 241 | 9507 | 1 | teamspeak3 |
| 4169 | 9507 | 1 | teamspeak3 |
| 188 | 9509 | 1 | teamspeak3 |
| 4177 | 9509 | 1 | teamspeak3 |
+-----------+-------------+----------------+-------------+
QUERY RESULT: 9501. When we used this port then next: 9502, 9503, 9504, 9505, 9507, 9508, 9509, 9510 etc.

Answer 1

SELECT data.sPort
FROM
((SELECT (s.server_port + 1) sPort
FROM pro_servers s
LEFT JOIN pro_servers sp1 ON sp1.server_port = s.server_port + 1
WHERE (sp1.server_port IS NULL)
ORDER BY sPort)
UNION ALL
(SELECT s.server_port sPost
FROM pro_servers s
GROUP BY s.server_port
HAVING COUNT(s.server_port) = SUM(s.server_deleted)
ORDER BY sPort)) AS data
ORDER BY data.sPort
LIMIT 1
SqlFiddle: http://sqlfiddle.com/#!2/12ab1/2
How it works
Left Join pro_servers with pro_servers with server_port = server_port + 1 join condition and take rows, where there is null in the next port. These rows shows first ports from every gap. The port Id can be taken as server_port + 1.
Take all deleted ports.
Union 1. and 2., order by server_port and take the first one.
There is one assumption for an answer - port with the lowest number is always taken. If it's not true, check that port separately (or add another UNION ALL to the query).

Answer 2

Also, you can try to index the table.
CREATE INDEX indexName ON tableName(field1 [,field2...]);

Answer 3

I don't know if this will be faster but it will certainly help you to avoid repeating same conditions twice:
SELECT
MAX(server_port) + 1 AS first_available_port
FROM (
SELECT
server_port,
#row := #row + 1 AS row
FROM
pro_servers AS s,
(SELECT #row := 0) AS x
WHERE server_port <> 0
AND server_type = 'ts3'
AND server_deleted = 0
) AS s
GROUP BY
server_port - row
ORDER BY
server_port - row
LIMIT 1
;
The inner query enumerates existing ports matching the conditions. Now, the difference between the port numbers and the row numbers will stay the same for rows belonging to the same group of consecutive rows. The outer query groups by that difference and returns the first group's highest port plus one.

Answer 4

I would use this query that uses NOT EXISTS:
SELECT MIN(server_port)+1
FROM pro_servers p1
WHERE
p1.server_type = 'ts3' AND
NOT EXISTS (SELECT server_port
FROM pro_servers p2
WHERE p1.server_port=p2.server_port-1
AND p1.server_type=p2.server_type
AND p2.server_deleted=0)
or this that uses a LEFT JOIN:
SELECT MIN(p1.server_port)+1
FROM
pro_servers p1 LEFT JOIN pro_servers p2
ON p1.server_port=p2.server_port-1
AND p1.server_type=p2.server_type
AND p2.server_deleted=0
WHERE
p2.server_port IS NULL
AND p1.server_type='ts3'
Please see fiddle here.