Feature summary (what you would like to be able to do and where):
When listing logevents using the API the "logpage" property is displayed. (Example)
It would be very useful to be able to search the logs by this property. Both using the api and using Special:Log user interface.

Use case(s) (list the steps that you performed to discover that problem, and describe the actual underlying problem which you want to solve. Do not describe only a solution):
I want to be able to show the logs of revision deletions for pages that have been moved. Currently to do this, you first need to know the old page title and look in different logs for the current title and any old titles of the page. Since "logpage" isn't changed when moving pages, by listing logs by "logpage" you only need to look in one log.

This is also useful for other types logs of moved pages. Maybe especially for move logs so you can follow page moves of a page without knowing the old page titles.

Benefits (why should this be implemented?):
This will make it easier to search all types of logs after a page has been moved.