The regular AR pluck method returns the values only, for instance:
Student.pluck(:firstname) => ["John", "Mike", "Simon"]
It'd be a nice feature to have a version which returns a hashes with the
column names as keys: [{ firstname: "John"}, { firstname: "Mike" }, {
firstname: "Simon" }]
I know this can (almost) be achieved with
Student.select(:firstname).map(&:attributes) (it forces you to have an id
attribute), but this involves instantiating lots of AR objects, which loses
the benefit of pluck.
An example implementation would be:
def self.hash_pluck(*keys)
pluck(*keys).map{ |vals| Hash[keys.zip(Array(vals))] }
end
In some (probably bad) benchmarks I made comparing this to the select
alternative, the select method was ~3.4x slower.
Benchmark.ips do |x|
x.report("hash_pluck") { Student.hash_pluck(:firstname) }
x.report("select") { Student.select(:firstname).map(&:attributes) }
x.compare!
end
Calculating -------------------------------------
select 6.000 i/100ms
hash_pluck 24.000 i/100ms
-------------------------------------------------
select 77.096 (±29.8%) i/s - 342.000
hash_pluck 265.316 (±41.8%) i/s - 1.104k
Comparison:
hash_pluck: 265.3 i/s
select: 77.1 i/s - 3.44x slower
Just thought that it might be a nice convenience method to have!
Cheers,
Mike
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