Sharded query with where.not running map/each goes to master shard

[MrBusch]

I've run into a query not returning the expected result and finally got it down to this minimum working example:

class Testquery
    def self.get_total(id)
        calendar_days = CalendarDay.using(:shard)\
                                   .where(id: id)\
                                   .where.not(price: nil)
        puts "Got #{calendar_days.count} entries"
        total = 0.0
        calendar_days.map { |cd|
            total += cd.price
        }
        puts total
    end

    def self.get_total2(id)
        calendar_days = CalendarDay.using(:shard)\
                                   .where(id: id)\
                                   .where('price IS NOT NULL')
        puts "Got #{calendar_days.count} entries"
        total = 0.0
        calendar_days.map { |cd|
            total += cd.price
        }
        puts total
    end
end

> ActiveRecord::Base.logger = Logger.new(STDOUT)
> Testquery.get_total(id)
Fetching calendar_days
D, [2019-02-22T18:41:19.231971 #20445] DEBUG -- : [Shard: shard]   (1.2ms)  SELECT COUNT(*) FROM "calendar_days" WHERE "calendar_days"."id" = $1 AND "calendar_days"."price" IS NOT NULL  [["id", 564815]]
Got 1929 entries: CalendarDay::ActiveRecord_Relation
D, [2019-02-22T18:41:19.232863 #20445] DEBUG -- : [Shard: master]  CalendarDay Load (0.5ms)  SELECT "calendar_days".* FROM "calendar_days" WHERE "calendar_days"."id" = $1 AND "calendar_days"."price" IS NOT NULL  [["id", 564815]]
0.0
=> nil
> Testquery.get_total2(id)
Fetching calendar_days
D, [2019-02-22T18:41:23.594372 #20445] DEBUG -- : [Shard: shard]   (1.2ms)  SELECT COUNT(*) FROM "calendar_days" WHERE "calendar_days"."id" = $1 AND (price IS NOT NULL)  [["id", 564815]]
Got 1929 entries: CalendarDay::ActiveRecord_Relation
D, [2019-02-22T18:41:23.600031 #20445] DEBUG -- : [Shard: shard]  CalendarDay Load (5.2ms)  SELECT "calendar_days".* FROM "calendar_days" WHERE "calendar_days"."id" = $1 AND (price IS NOT NULL)  [["id", 564815]]
312784.0
=> nil

The difference between the two queries is that the first uses the ActiveRecord way of where.not(price: nil) while the second uses where('price IS NOT NULL'). If I use where.not, the evaluation when invoking map goes to :master even though a shard is specified. Contrary to that the prior call to count correctly goes to the shard. I also tested each in place of map and both had the same result.

So the combination of defining a non-master shard, querying with where.not and then running map/each does not evaluate the query to the correct shard.