In all our application we connect to MySQL database as single db user, and we need to pass the end user id to the mysql database?

So how can we pass it?

I've idea to create plugin to add mysql variables ex. "app_userid" and set it when user login??!!

but i don't have any idea how to create plugin?

Or do you have another idea??

Note: i don't want to change the application code, and i need it

In large vBulletin forum we had strange problem in memory table "session", we've 25M post, 1.7M user, 20K online user.So we change engine of session table to InnoDB and set configuration of innoDB as follow (be careful this configuration is not proper for other tables because this is good in performance but bad in crash and recovery, and data reliability)innodb_data_home_dir = /dev/shm/mysql/

Here are some common performance tuning concepts that I frequently run into. Please note that this really is only a basic introduction to performance tuning. For more in-depth tuning, it strongly depends on your systems, data and usage. Server Variables For tuning InnoDB performance, your primary variable is innodb_buffer_pool_size. This is the chunk of memory that InnoDB uses for caching data,

If this can be of any interest, the following is the list of new variables included in MySQL™ v.6.0.6-alpha. Maria-variables already included in prev. binary versions (like 5.1.23-maria) are not count here.

1. falcon_checksums: (default ON) to calculate and verify page checksums.
2. falcon_serial_log_file_size: not documented.
3. falcon_use_sectorcache:  not documented.
4. falcon_use_supernodes: not documented.
5. maria_force_start_after_recovery_failures: Number of consecutive log recovery failures after which logs will be automatically deleted to cure the problem; 0 (the default) disables the feature.
6. maria_recover: Specifies how corrupted tables should be automatically repaired.

No new status variables have been included. …