Cannot filter on collections with only one character as name

[runarbu]

Both the rest api and admin gui allow users to add collections with a single character as collection name. Unfortunately the search kernel won't allow us to filter so short names. For what I can see the query parser at src/query is filtering out this already before it reaches the search kernel.

To replicate:

• Make a collection named “n”
• Try to filter on that collection

Also try src/query/query_parser "omp collection:f" vs src/query/query_parser "omp collection:ff"