Dealing with Duplicates in DEVONthink
Duplicates in DEVONthink are great when you need them, not so great when you don't. But how to track them down and get rid of them?
In your database you will find a built-in smart group, a purple folder with a gear icon on it, called Duplicates. Selecting this folder will show you the files that are duplicated. (Depending on your settings in Preferences > General, duplicate files may be shown in blue.) So how do you manage them?
In the menu Scripts > Data (Scripts looks like a stylized 'S') there is a script called Move Duplicates To Trash. If you select files in the Duplicates smart group (any or all) and run this script, all but the most recently added instance of each set of duplicates will be sent to the database's trash. Quick and easy cleanup. But…
Maybe you're using DEVONthink Personal or you want to control what file gets trashed and what one stays. Select a file and choose Data > See Also & Classify (or click the magic hat icon) to open the See Also drawer. You'll notice the file is listed at the top multiple times with the database location under the name. (The green bar next to the name is a quick visual hint that they are matches.) From here you can right-click to Reveal the file in the database or choose Move All Instances to Trash. Yes, this works on multiple selected files.
Note this does not apply to replicants as there is truly only one file with a replicant.
One last note: A duplicate is not necessarily a byte-for-byte duplicate but can also be a 'close match'. When you use the second option above, you could select Open from the context menu and edit the file and you would see the green bar on the edited file has turned gray and is shorter. DEVONthink will consider it a close match but no longer a duplicate, even if the name was still the same. It won't be something so small as adding a comma to break the duplicate status though. (Think about it — if the only difference in two things you've read is a single comma or sentence, you'd functionally consider them the same.)