MySQL

I've been working with MySQL since 2005 and before that the Pick/D3 database since 1998 and I have brief experience with postgress, both installing and supporting the products.

I've used both MySQL and Pick/D3 in a High Availability solution (master-slave replication) for trading platforms.

I've also used MySQL slaves as a redundancy/backup solution (across continents) to guarantee data in the event of total failure at a one location (a backOffice trading application for a Financial Services provider and at a PoP for an ISP) the geographically remote would have an up to the second DR copy.  This included constant monitoring of the solution to confirm it was working.

One of the lessons learned early on (from a Support Manager) was not to trust only the DBMS tools to know if a replicated solution was in-sync, but rather to establish one or more business relevant metrics and compare master and slave record sets on those.

• I have been involved in high performance requirements and I have ongoing experience in diagnosing and taking action where slow queries need attention.
• I've used the MySQL UDF library along with triggers and stored procedures to creatively solve a business problem that could not be resolve otherwise.
• I have used Views to colate and segment data to allow stricly permissioned SQL level access for end-users to run queries without risk.
• I have (controversially depending on your PoV) placed business logic in stored procedures to make business data more available to folk with SQL skills (so that these requests could be serviced without programmer time)

To get an idea of scale, here are the outputs of the status command a main and slave server:

Main

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 16014786
Server version: 5.0.77-log Source distribution

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> status
--------------
mysql  Ver 14.12 Distrib 5.0.77, for redhat-linux-gnu (x86_64) using readline 5.1

Connection id:          16014786
Current database:       
Current user:           root@localhost
SSL:                    Not in use
Current pager:          stdout
Using outfile:          ''
Using delimiter:        ;
Server version:         5.0.77-log Source distribution
Protocol version:       10
Connection:             Localhost via UNIX socket
Server characterset:    latin1
Db     characterset:    latin1
Client characterset:    latin1
Conn.  characterset:    latin1
UNIX socket:            /var/lib/mysql/mysql.sock
Uptime:                 99 days 11 hours 25 sec

Threads: 36  Questions: 19158580012  Slow queries: 9530  Opens: 27952745  Flush tables: 4  Open tables: 64  Queries per second avg: 2229.498
--------------

mysql>

Slave

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 557832
Server version: 5.0.77 Source distribution

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
 
mysql> status
--------------
mysql  Ver 14.12 Distrib 5.0.77, for redhat-linux-gnu (x86_64) using readline 5.1

Connection id:          557832
Current database:       
Current user:           root@localhost
SSL:                    Not in use
Current pager:          stdout
Using outfile:          ''
Using delimiter:        ;
Server version:         5.0.77 Source distribution
Protocol version:       10
Connection:             Localhost via UNIX socket
Server characterset:    latin1
Db     characterset:    latin1
Client characterset:    latin1
Conn.  characterset:    latin1
UNIX socket:            /var/lib/mysql/mysql.sock
Uptime:                 22 days 16 hours 7 min 48 sec

Threads: 43  Questions: 2610068396  Slow queries: 748  Opens: 461544  Flush tables: 1  Open tables: 64  Queries per second avg: 1332.437
--------------

mysql>