Description:
Sometimes, autocompletion is turned on in SQL pane of query editor. It tries to
complete current word to SQL keyword. But it works incorrectly: sometimes it
tries to complete word starting from first typed letter, though word starts earlier.

Example: after current SQL type 
wherywge, then use backspace to remove all letters except w. Now pressing 'h'
causes auto-completion to suggest HAVING keyword instead of WHERE or WHEN.