Class: ActiveRecord::InternalMetadata

Inherits:
Object
  • Object
show all
Defined in:
lib/active_record/internal_metadata.rb

Overview

This class is used to create a table that keeps track of values and keys such as which environment migrations were run in.

This is enabled by default. To disable this functionality set ‘use_metadata_table` to false in your database configuration.

Defined Under Namespace

Classes: NullInternalMetadata

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(pool) ⇒ InternalMetadata

Returns a new instance of InternalMetadata.



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# File 'lib/active_record/internal_metadata.rb', line 18

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/internal_metadata.rb', line 16

def arel_table
  @arel_table
end

Instance Method Details

#[](key) ⇒ Object 



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# File 'lib/active_record/internal_metadata.rb', line 47

def [](key)
  return unless enabled?

  @pool.with_connection do |connection|
    if entry = select_entry(connection, key)
      entry[value_key]
    end
  end
end

#[]=(key, value) ⇒ Object 



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# File 'lib/active_record/internal_metadata.rb', line 39

def []=(key, value)
  return unless enabled?

  @pool.with_connection do |connection|
    update_or_create_entry(connection, key, value)
  end
end

#count ⇒ Object 



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# File 'lib/active_record/internal_metadata.rb', line 65

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

Creates an internal metadata table with columns key and value



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# File 'lib/active_record/internal_metadata.rb', line 85

def create_table
  return unless enabled?

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

#create_table_and_set_flags(environment, schema_sha1 = nil) ⇒ Object 



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# File 'lib/active_record/internal_metadata.rb', line 74

def create_table_and_set_flags(environment, schema_sha1 = nil)
  return unless enabled?

  @pool.with_connection do |connection|
    create_table
    update_or_create_entry(connection, :environment, environment)
    update_or_create_entry(connection, :schema_sha1, schema_sha1) if schema_sha1
  end
end

#delete_all_entries ⇒ Object 



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# File 'lib/active_record/internal_metadata.rb', line 57

def delete_all_entries
  dm = Arel::DeleteManager.new(arel_table)

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

#drop_table ⇒ Object 



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# File 'lib/active_record/internal_metadata.rb', line 99

def drop_table
  return unless enabled?

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

#enabled? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/active_record/internal_metadata.rb', line 35

def enabled?
  @pool.db_config.use_metadata_table?
end

#primary_key ⇒ Object 



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# File 'lib/active_record/internal_metadata.rb', line 23

def primary_key
  "key"
end

#table_exists? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/active_record/internal_metadata.rb', line 107

def table_exists?
  @pool.schema_cache.data_source_exists?(table_name)
end

#table_name ⇒ Object 



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# File 'lib/active_record/internal_metadata.rb', line 31

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

#value_key ⇒ Object 



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# File 'lib/active_record/internal_metadata.rb', line 27

def value_key
  "value"
end