Class: ActiveRecord::Associations::AliasTracker

Inherits:
Object
  • Object
show all
Defined in:
activerecord/lib/active_record/associations/alias_tracker.rb

Overview

Keeps track of table aliases for ActiveRecord::Associations::JoinDependency

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(connection, aliases) ⇒ AliasTracker

table_joins is an array of arel joins which might conflict with the aliases we assign here



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# File 'activerecord/lib/active_record/associations/alias_tracker.rb', line 46

def initialize(connection, aliases)
  @aliases    = aliases
  @connection = connection
end

Instance Attribute Details

#aliases ⇒ Object (readonly)

Returns the value of attribute aliases



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# File 'activerecord/lib/active_record/associations/alias_tracker.rb', line 72

def aliases
  @aliases
end

Class Method Details

.create(connection, initial_table, joins) ⇒ Object 



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# File 'activerecord/lib/active_record/associations/alias_tracker.rb', line 9

def self.create(connection, initial_table, joins)
  if joins.empty?
    aliases = Hash.new(0)
  else
    aliases = Hash.new { |h, k|
      h[k] = initial_count_for(connection, k, joins)
    }
  end
  aliases[initial_table] = 1
  new(connection, aliases)
end

.initial_count_for(connection, name, table_joins) ⇒ Object 



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# File 'activerecord/lib/active_record/associations/alias_tracker.rb', line 21

def self.initial_count_for(connection, name, table_joins)
  quoted_name = nil

  counts = table_joins.map do |join|
    if join.is_a?(Arel::Nodes::StringJoin)
      # quoted_name should be case ignored as some database adapters (Oracle) return quoted name in uppercase
      quoted_name ||= connection.quote_table_name(name)

      # Table names + table aliases
      join.left.scan(
        /JOIN(?:\s+\w+)?\s+(?:\S+\s+)?(?:#{quoted_name}|#{name})\sON/i
      ).size
    elsif join.is_a?(Arel::Nodes::Join)
      join.left.name == name ? 1 : 0
    elsif join.is_a?(Hash)
      join[name]
    else
      raise ArgumentError, "joins list should be initialized by list of Arel::Nodes::Join"
    end
  end

  counts.sum
end

Instance Method Details

#aliased_table_for(table_name, aliased_name, type_caster) ⇒ Object 



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# File 'activerecord/lib/active_record/associations/alias_tracker.rb', line 51

def aliased_table_for(table_name, aliased_name, type_caster)
  if aliases[table_name].zero?
    # If it's zero, we can have our table_name
    aliases[table_name] = 1
    Arel::Table.new(table_name, type_caster: type_caster)
  else
    # Otherwise, we need to use an alias
    aliased_name = @connection.table_alias_for(aliased_name)

    # Update the count
    aliases[aliased_name] += 1

    table_alias = if aliases[aliased_name] > 1
      "#{truncate(aliased_name)}_#{aliases[aliased_name]}"
    else
      aliased_name
    end
    Arel::Table.new(table_name, type_caster: type_caster).alias(table_alias)
  end
end