docs/sql/README.md
# SQL feature overview
#### Universal requirements:
- [PHP Data Objects (PDO)](http://php.net/manual/en/book.pdo.php) extension
- [PDO driver](http://php.net/manual/en/pdo.drivers.php) to communicate with the SQL server
## Robots.txt Cache
Every `robots.txt` parser needs some sort of a caching system.
By caching data to the SQL server, overall performance is increased, you'll limit the number of network lags and timeouts to a bare minimum, and last but not least, no more spamming of the remote host.
[Enable the built-in caching system.](cache.md)
## Delay handler
Many hosts requires you to control the robot's request flow, using a minimum interval between each request.
[Learn how to honor the delay directives.](delay.md)