What is the benefit of this method?
You can pluck(:firstname).map { |e| { firstname: e } } if you really wanted
that. Why are you plucking and wanting it to be a hash?
> On 25 Jun 2015, at 19:59, Mike Campbell <[email protected]> wrote:
>
> 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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