Changing a page's parent does not change the page's guid

[truthandcoffee]

When making a change to the parent/child relationship of two existing pages, the guid of the child page does not update to reflect the new association. For example, if I have:

(www.somesite.com)

• Existing Page 1 (slug: page1)
• Existing Page 2 (slug: page2)

guid of 'Existing Page 1' is '​http://www.somesite.com/page1'
guid of 'Existing Page 2' is '​http://www.somesite.com/page2'

If I create a brand new 'Page 3', and set it as a child of 'Existing Page 1', the guid of 'Page 3' is '​http://www.somesite.com/page1/page3'. This is exactly how it should be.

But, if I go back and assign 'Existing Page 2' to be a child of 'Existing Page 1', the guid of 'Existing Page 2' does not change to reflect the new relationship, but instead stays as '​http://www.somesite.com/page2', whereas it seems as it should become '​http://www.somesite.com/page1/page2'.

Although it looks like an URL, the guid is a ​globally unique identifier, not a URL. The important thing is that it's unique to that page.

It is e.g. used for things like RSS feeds, where the reader/aggregator will decide if it's the same post based on the guid. It's kind of counterintuitive though because it looks like the_permalink().