When I was trying to implement the Auto-Complete suggestion in our product, I faced lots of difficulties to make it a good feature. Using OpenSearch was our constrain as we are using OpenSearch as our index database, so I had to use OpenSearch to solve the problem, first I used normal match query to match the text but the results was very poor, as I was getting results that should not be there, then I dig and find wildcard and match_phrase_prefix queries, but both were having problems when I was using longer texts to search which has spaces. So these are not working with spaces in search terms. Then after doing lot of research, I find out that OpenSearch also maintains the keyword mappings that can be used to search the exact term without any tokens and analysers, so I thought to use wildcard query with keyword mapping fields, and it works like a wow.
I hope this will help you guys to solve the problem.
