Class: OnlineMigrations::BackgroundDataMigrations::ResetCounters

Inherits:
DataMigration
  • Object
show all
Defined in:
lib/online_migrations/background_data_migrations/reset_counters.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods inherited from DataMigration

#after_cancel, #after_complete, #after_pause, #after_resume, #after_start, #after_stop, #around_process, #build_enumerator, collection_batch_size, named

Constructor Details

#initialize(model_name, counters, options = {}) ⇒ ResetCounters

Returns a new instance of ResetCounters.



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# File 'lib/online_migrations/background_data_migrations/reset_counters.rb', line 9

def initialize(model_name, counters, options = {})
  @model = Object.const_get(model_name, false)
  @counters = counters
  @touch = options[:touch]
end

Instance Attribute Details

#counters ⇒ Object (readonly)

Returns the value of attribute counters.



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# File 'lib/online_migrations/background_data_migrations/reset_counters.rb', line 7

def counters
  @counters
end

#model ⇒ Object (readonly)

Returns the value of attribute model.



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# File 'lib/online_migrations/background_data_migrations/reset_counters.rb', line 7

def model
  @model
end

#touch ⇒ Object (readonly)

Returns the value of attribute touch.



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# File 'lib/online_migrations/background_data_migrations/reset_counters.rb', line 7

def touch
  @touch
end

Instance Method Details

#collection ⇒ Object 



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# File 'lib/online_migrations/background_data_migrations/reset_counters.rb', line 15

def collection
  model.unscoped.in_batches(of: 100)
end

#count ⇒ Object 



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# File 'lib/online_migrations/background_data_migrations/reset_counters.rb', line 50

def count
  # Exact counts are expensive on large tables, since PostgreSQL
  # needs to do a full scan. An estimated count should give a pretty decent
  # approximation of rows count in this case.
  Utils.estimated_count(connection, model.table_name)
end

#process(relation) ⇒ Object 



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# File 'lib/online_migrations/background_data_migrations/reset_counters.rb', line 19

def process(relation)
  updates = counters.map do |counter_association|
    has_many_association = has_many_association(counter_association)

    foreign_key  = has_many_association.foreign_key.to_s
    child_class  = has_many_association.klass
    reflection   = child_class._reflections.values.find { |e| e.belongs_to? && e.foreign_key.to_s == foreign_key && e.options[:counter_cache].present? }
    counter_name = reflection.counter_cache_column

    quoted_association_table = connection.quote_table_name(has_many_association.table_name)
    count_subquery = "      SELECT COUNT(*)\n      FROM \#{quoted_association_table}\n      WHERE \#{quoted_association_table}.\#{connection.quote_column_name(foreign_key)} =\n        \#{model.quoted_table_name}.\#{model.quoted_primary_key}\n    SQL\n\n    \"\#{connection.quote_column_name(counter_name)} = (\#{count_subquery})\"\n  end\n\n  if touch\n    names = touch if touch != true\n    names = Array.wrap(names)\n    options = names.extract_options!\n    touch_updates = touch_attributes_with_time(*names, **options)\n    updates << model.sanitize_sql_for_assignment(touch_updates)\n  end\n\n  relation.update_all(updates.join(\", \"))\nend\n"