How to check if a number is within range in activerecord?

问题

I have a model with a range column

#<JobRequirement id: 1, age: 18...30>

How can I get the JobRequirement using an age: 20?

Something like

JobRequirement.where(age: 20)

回答1:

I think you need to use the PostgreSQL range operators and a bit of SQL in a string. In particular, you'd want the @> (contains element) operator:

JobRequirement.where('age @> ?', 20)

As far as supplying a range as a placeholder value goes:

JobRequirement.where('age <@ ?', 18..20)

you'll find that AR's knowledge of PostgreSQL's range types is somewhat limited. When you supply a range as a value for a placeholder, AR will want to expand the range to a comma delimited list as it assumes that you're saying something like where('col in (?)', 18..20) so you end up with nonsense like:

where age <@ 18,19,20

in the generated SQL. You can get around this by manually type casting the value; for example:

> ActiveRecord::Base.connection.type_cast(6..11)
 => "[6,11]" 
> ActiveRecord::Base.connection.type_cast(6...11)
 => "[6,11)" 

and then sending the string into the query where PostgreSQL should cast it to a PostgreSQL-range automatically:

JobRequirement.where('age <@ ?', ActiveRecord::Base.connection.type_cast(18..20))

Depending on where you're doing this, the connection method might be available with all the noise:

JobRequirement.where('age <@ ?', connection.type_cast(18..20))

And if PostgreSQL isn't picking the right version of the <@ operator on its own then you can help it with more typecasting:

JobRequirement.where('age <@ ?::int4range', connection.type_cast(18..20))

来源：https://stackoverflow.com/questions/51573800/how-to-check-if-a-number-is-within-range-in-activerecord