Originally Posted by capnm
(Though I don't see why that should affect this and not Extract ISBN).
Perhaps this may give a hint to chaley/Kovid where the problem lies. Extract ISBN is affecting identifiers, whereas this plugin is affecting custom columns. Incidentially neither of these plugins has any interaction with the tag browser directly, not even a call to refresh. Extract ISBN probably should have a refresh call added to it (since there is a count of identifiers which may be affected) but the pages/word count columns are not visible so there is no need for this plugin.
So quite why the tag browser is having memory issues when the plugin is doing nothing with it is a mystery best left for chaley - perhaps it is listening to some events or something. As was mentioned previously both these plugins are deferring all database updates to the Calibre code that exists in edit_metadata.py which is called when the user finishes downloading metadata.