Expand and improve #pluck docs
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@ -108,15 +108,36 @@ def calculate(operation, column_name, options = {})
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0
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end
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# This method is designed to perform select by a single column as direct SQL query
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# Returns <tt>Array</tt> with values of the specified column name
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# The values has same data type as column.
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# Use <tt>pluck</tt> as a shortcut to select a single attribute without
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# loading a bunch of records just to grab one attribute you want.
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#
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# Person.pluck(:name)
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#
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# instead of
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#
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# Person.all.map(&:name)
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#
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# Pluck returns an <tt>Array</tt> of attribute values type-casted to match
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# the plucked column name, if it can be deduced. Plucking a SQL fragment
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# returns String values by default.
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#
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# Examples:
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#
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# Person.pluck(:id) # SELECT people.id FROM people
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# Person.uniq.pluck(:role) # SELECT DISTINCT role FROM people
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# Person.where(:age => 21).limit(5).pluck(:id) # SELECT people.id FROM people WHERE people.age = 21 LIMIT 5
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# Person.pluck(:id)
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# # SELECT people.id FROM people
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# # => [1, 2, 3]
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#
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# Person.uniq.pluck(:role)
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# # SELECT DISTINCT role FROM people
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# # => ['admin', 'member', 'guest']
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#
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# Person.where(:age => 21).limit(5).pluck(:id)
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# # SELECT people.id FROM people WHERE people.age = 21 LIMIT 5
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# # => [2, 3]
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#
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# Person.pluck('DATEDIFF(updated_at, created_at)')
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# # SELECT DATEDIFF(updated_at, created_at) FROM people
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# # => ['0', '27761', '173']
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#
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def pluck(column_name)
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key = column_name.to_s.split('.', 2).last
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