Question

Hows does Drupal 6 interact with MySQL for connections and transactions? Does connection pooling get used? How are transactions handled? At what level are these things managed by Drupal vs being handed off to be handled by MySQL?

I did a good amount of searching on the web and within Stack Overflow, but mainly, I only found articles for tweaking Drupal performance and scaling needs.

Answer 1

From Acquia support team,

The number of connections would vary based on activity but you can boil it down as you mention here, one request per user request. There is no concept of connection pooling or persistent connections in Drupal.

Sometimes it helps to get a handle on
the Database Abstraction Layer (how
Drupal talks to the database) and the
bootstrap process (See
http://api.drupal.org/api/drupal/includes–bootstrap.inc/6)
for a more detailed walk of how it
works.