Class: ActiveRecord::SchemaMigration

Inherits:
Object
  • Object
show all
Defined in:
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.

Defined Under Namespace

Classes: NullSchemaMigration

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(pool) ⇒ SchemaMigration

Returns a new instance of SchemaMigration.



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# File '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 ⇒ Object (readonly)

Returns the value of attribute arel_table.



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

def arel_table
  @arel_table
end

Instance Method Details

#count ⇒ Object 



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# File '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 ⇒ Object 



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# File '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) ⇒ Object 



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# File '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 ⇒ Object 



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# File '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) ⇒ Object 



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# File '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 ⇒ Object 



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# File '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 ⇒ Object 



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

def integer_versions
  versions.map(&:to_i)
end

#normalize_migration_number(number) ⇒ Object 



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

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

#normalized_versions ⇒ Object 



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

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

#primary_key ⇒ Object 



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

def primary_key
  "version"
end

#table_exists? ⇒ Boolean

Returns:

  • (Boolean) 


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

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

#table_name ⇒ Object 



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# File '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 ⇒ Object 



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# File '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