When an RSS Feed is requested, Confluence renders all pages into the resulting XML.

This can be computationally intensive for certain macros, especially the SQL Macro.

If people are subscribed to wide-ranging feeds such as 'New Pages' or 'Changed Pages', this can cause many such pages to render. Many of these rendering passes are for no benefit to humans, since RSS Readers refresh feeds on a regular basis, especially Google Reader which refreshes every 30 minutes even if nobody is currently using Google Reader!

Further, the feeds cannot be cached because they are dependent upon each individual user's security privileges.

The result: Goole Reader refreshes the feed 48 times a day, causing computationally intesive pages to render for no human benefit, and it does this for every separate user who has subscribed. Other RSS Readers update less frequently, but still annoyingly.

Recommendation: Do not render the SQL macro in RSS Feeds. There may also be other macros that are best avoided. (Perhaps a flag in the plugin that indicates whether to render in RSS Feeds?)

It is especially the case on Atlassian's own Extranet that this causes high load.