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Like this: Like Loading If found; the identifier is returned. In this case, a new connection is not established. Hence, it will save time if you have already established your connection. Hence will need more memory at run time making it more complex.
If one is found, an identifier for it will be returned instead of opening a new connection. Second, the connection to the SQL server will not be closed when the execution of the script ends. Other Related Discussions. Hi Good day to all,. Changing some col. How do i? What are different types of statements supported by SQL? What is a Stored Procedure? So you see a lot of wasted resources for no purpose if the connections are idle.
I don't know if you'll reach 10, idle connections, but even a couple of hundred is costly. Connections have state, and it would be inappropriate for a PHP request to "inherit" information from a session previously used by another PHP request. For example, temporary tables and user variables are normally cleaned up as a connection closes, but not if you use persistent connections.
Likewise session-based settings like character set and collation. For MySQL at least, the downside of persistent connections probably outweighs their benefits. And there are other, better techniques to achieve high scalability. In MySQL 5. And this work has accelerated in MySQL 5. In this blog post I will first show the results we have achieved and then describe what we have done to get them. Basically you have to balance the cost of creating connections versus keeping connections.
This is noticeable on a high-enough traffic site. Unfortunately, PHP does not have any controls on the persistence of connections. So the answer is to lower the idle timeout in MySQL a long way like down to 20 seconds , and to up the thread cache size. Together, this generally works remarkably well. On the flip side, your application needs to respect the state of the connection.
It is best if it makes no assumptions about what state the session is in. First, when connecting, the function would try to find a persistent connection that's already open with the same host, username and password. If one is found, an identifier for it will be returned instead of opening a new connection. Second, the connection to the SQL server will not be closed when the execution of the script ends. At that time for every request it will not open a connection but will take it from the pool.
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