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Class: ActiveRecord::SchemaMigration

Do not use. This class is for internal use only.
Relationships & Source Files
Namespace Children
Classes:
NullSchemaMigration
Inherits: Object
Defined in: activerecord/lib/active_record/schema_migration.rb

Overview

This class is used to create a table that keeps track of which migrations have been applied to a given database. When a migration is run, its schema number is inserted in to the schema migrations table so it doesn’t need to be executed the next time.

Class Method Summary

Instance Attribute Summary

Instance Method Summary

Constructor Details

.new(pool) ⇒ SchemaMigration

[ GitHub ] 

  


# File 'activerecord/lib/active_record/schema_migration.rb', line 14



def initialize(pool)
  @pool = pool
  @arel_table = Arel::Table.new(table_name)
end


  







Instance Attribute Details



  

    #arel_table   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/schema_migration.rb', line 12



attr_reader :arel_table


  








  

    #table_exists?  ⇒ Boolean  (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/schema_migration.rb', line 100



def table_exists?
  @pool.with_connection do |connection|
    connection.data_source_exists?(table_name)
  end
end


  







Instance Method Details



  

    #count  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/schema_migration.rb', line 91



def count
  sm = Arel::SelectManager.new(arel_table)
  sm.project(*Arel::Nodes::Count.new([Arel.star]))

  @pool.with_connection do |connection|
    connection.select_values(sm, "#{self.class} Count").first
  end
end


  








  

    #create_table  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/schema_migration.rb', line 53



def create_table
  @pool.with_connection do |connection|
    unless connection.table_exists?(table_name)
      connection.create_table(table_name, id: false) do |t|
        t.string :version, **connection.internal_string_options_for_primary_key
      end
    end
  end
end


  








  

    #create_version(version)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/schema_migration.rb', line 19



def create_version(version)
  im = Arel::InsertManager.new(arel_table)
  im.insert(arel_table[primary_key] => version)
  @pool.with_connection do |connection|
    connection.insert(im, "#{self.class} Create", primary_key, version)
  end
end


  








  

    #delete_all_versions  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/schema_migration.rb', line 36



def delete_all_versions
  # Eagerly check in connection to avoid checking in/out many times in the called method.
  @pool.with_connection do
    versions.each do |version|
      delete_version(version)
    end
  end
end


  








  

    #delete_version(version)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/schema_migration.rb', line 27



def delete_version(version)
  dm = Arel::DeleteManager.new(arel_table)
  dm.wheres = [arel_table[primary_key].eq(version)]

  @pool.with_connection do |connection|
    connection.delete(dm, "#{self.class} Destroy")
  end
end


  








  

    #drop_table  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/schema_migration.rb', line 63



def drop_table
  @pool.with_connection do |connection|
    connection.drop_table table_name, if_exists: true
  end
end


  








  

    #integer_versions  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/schema_migration.rb', line 87



def integer_versions
  versions.map(&:to_i)
end


  








  

    #normalize_migration_number(number)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/schema_migration.rb', line 69



def normalize_migration_number(number)
  "%.3d" % number.to_i
end


  








  

    #normalized_versions  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/schema_migration.rb', line 73



def normalized_versions
  versions.map { |v| normalize_migration_number v }
end


  








  

    #primary_key  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/schema_migration.rb', line 45



def primary_key
  "version"
end


  








  

    #table_name  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/schema_migration.rb', line 49



def table_name
  "#{ActiveRecord::Base.table_name_prefix}#{ActiveRecord::Base.schema_migrations_table_name}#{ActiveRecord::Base.table_name_suffix}"
end


  








  

    #versions  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/schema_migration.rb', line 77



def versions
  sm = Arel::SelectManager.new(arel_table)
  sm.project(arel_table[primary_key])
  sm.order(arel_table[primary_key].asc)

  @pool.with_connection do |connection|
    connection.select_values(sm, "#{self.class} Load")
  end
end