Class: JobIteration::ActiveRecordCursor

Inherits:
Object
  • Object
show all
Includes:
Comparable
Defined in:
lib/job-iteration/active_record_cursor.rb

Overview

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Defined Under Namespace

Classes: ConditionNotSupportedError

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(relation, columns = nil, position = nil) ⇒ ActiveRecordCursor

Returns a new instance of ActiveRecordCursor.

Raises:

  • (ArgumentError) 


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# File 'lib/job-iteration/active_record_cursor.rb', line 21

def initialize(relation, columns = nil, position = nil)
  @columns = if columns
    Array(columns)
  else
    Array(relation.primary_key).map { |pk| "#{relation.table_name}.#{pk}" }
  end
  self.position = Array.wrap(position)
  raise ArgumentError, "Must specify at least one column" if columns.empty?
  if relation.joins_values.present? && !@columns.all? { |column| column.to_s.include?(".") }
    raise ArgumentError, "You need to specify fully-qualified columns if you join a table"
  end

  if relation.arel.orders.present? || relation.arel.taken.present?
    raise ConditionNotSupportedError
  end

  @base_relation = relation.reorder(@columns.join(","))
  @reached_end = false
end

Instance Attribute Details

#position ⇒ Object

Returns the value of attribute position.



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# File 'lib/job-iteration/active_record_cursor.rb', line 9

def position
  @position
end

#reached_end ⇒ Object

Returns the value of attribute reached_end.



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# File 'lib/job-iteration/active_record_cursor.rb', line 10

def reached_end
  @reached_end
end

Instance Method Details

#<=>(other) ⇒ Object 



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# File 'lib/job-iteration/active_record_cursor.rb', line 41

def <=>(other)
  if reached_end != other.reached_end
    reached_end ? 1 : -1
  else
    position <=> other.position
  end
end

#next_batch(batch_size) ⇒ Object 



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# File 'lib/job-iteration/active_record_cursor.rb', line 67

def next_batch(batch_size)
  return if @reached_end

  relation = @base_relation.limit(batch_size)

  if (conditions = self.conditions).any?
    relation = relation.where(*conditions)
  end

  records = relation.uncached do
    relation.to_a
  end

  update_from_record(records.last) unless records.empty?
  @reached_end = records.size < batch_size

  records.empty? ? nil : records
end

#update_from_record(record) ⇒ Object 



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# File 'lib/job-iteration/active_record_cursor.rb', line 55

def update_from_record(record)
  self.position = @columns.map do |column|
    method = column.to_s.split(".").last

    if ActiveRecord.version >= Gem::Version.new("7.1.0.alpha") && method == "id"
      record.id_value
    else
      record.send(method.to_sym)
    end
  end
end