Hi!
I tried searching for a few DOIs today which are string properties (i.e. 10.1371/JOURNAL.PCBI.1002947) and didn't get any results.
Statements are indexed, but you have to use haswbstatement with specific property to look for them.
Is this the phabricator task for this: https://phabricator.wikimedia.org/T163642 ?
This is the task to make strings searchable _without_ haswbstatement keyword.