Attribute filtering, or simply "filtering," is a basic function desired by users of vector databases. However, such a simple function faces great complexity.
Suppose Steve saw a photograph of a fashion blogger on a social media platform. He would like to search for a similar jean jacket on an online shopping platform that supports image similarity search. After uploading the image to the platform, Steve was shown a plethora of results of similar jean jackets. However, he only wears Levi’s. Then the results of image similarity search need to be filtered by brand. But the problem is when to apply the filter? Should it be applied before or after approximate nearest neighbor search (ANNS)?