You should ask this on the pathauto project space (http://drupal.org/project/pathauto) for the best answer. I do know that there was an issue where everytime a new node was displayed a call was made to check every alias to see if there was one for the node, with millions of aliases this could really slow down a site. I think there might have been a change to fix this, but you should ask on the project space.
Personally, I don't think there is a huge need for aliasing all nodes, it doesn't effect search much and people don't memorize any links except basic ones anyways. I think it's mostly only useful for blogs or articles where you feel a need for a date in the url, but really this is just cosmetic.
Although it doesn't work in every situation, there has been some interesting discussion regarding "grouped url aliasing" here. Drupal's url_aliasing is inherently slow, even with all patches applied :-(. Until somebody comes up with a seriously different paradigm the best option is to keep as few url aliases as practical (a few thousand say). Unless you have some huge database cluster at your disposal.....
Comments
Ask on project space
You should ask this on the pathauto project space (http://drupal.org/project/pathauto) for the best answer. I do know that there was an issue where everytime a new node was displayed a call was made to check every alias to see if there was one for the node, with millions of aliases this could really slow down a site. I think there might have been a change to fix this, but you should ask on the project space.
Personally, I don't think there is a huge need for aliasing all nodes, it doesn't effect search much and people don't memorize any links except basic ones anyways. I think it's mostly only useful for blogs or articles where you feel a need for a date in the url, but really this is just cosmetic.
Different approaches for different problems.
Although it doesn't work in every situation, there has been some interesting discussion regarding "grouped url aliasing" here. Drupal's url_aliasing is inherently slow, even with all patches applied :-(. Until somebody comes up with a seriously different paradigm the best option is to keep as few url aliases as practical (a few thousand say). Unless you have some huge database cluster at your disposal.....
Sigh,
James Andres
Lead Developer on Project Opus
www.projectopus.com
roundup note
I know that FiReaNG3L has seen this, but for others who might come here please go check out this issue: http://drupal.org/node/63635
Also, note about the scalability..."It's not a pathauto problem, it's just that pathauto does a wonderful job of highlighting this problem."
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