LIKE vs. = yields different index decision

Playing with CBO on beer-sample, after doing:

     ANALYZE ANALYTICS COLLECTION _default;

I noticed that:

     SELECT * FROM _default WHERE city = 'San Diego';

uses a city index if you create one:

     CREATE INDEX city_index ON _default(city: string);

However, the following seemingly equivalent query doesn't:

     SELECT * FROM _default WHERE city LIKE 'San Diego';

Interestingly, the selectivity estimate for both queries is identical but the cost estimates and decision are not.  For the equality case, the top of the plan says:

       "optimizer-estimates":

{            "cardinality": 0.73,            "op-cost": 0,            "total-cost": 2.59        }

vs. what it says for the LIKE case:

    "optimizer-estimates":

{            "cardinality": 0.73,            "op-cost": 0,            "total-cost": 7336.16     }

The index should be picked, one would think?

This is not CBO's fault, it seems, as if you disable CBO the behavior is the same.  I confirmed that the candidate AsterixDB release shares this issue.

We should use the index in this case!  (Both in RBO and in CBO.)