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require 'active_support/core_ext/string/conversions'
module ActiveRecord
module Associations
# Keeps track of table aliases for ActiveRecord::Associations::ClassMethods::JoinDependency and
# ActiveRecord::Associations::ThroughAssociationScope
class AliasTracker # :nodoc:
attr_reader :aliases, :connection
def self.empty(connection)
new connection, Hash.new(0)
end
def self.create(connection, table_joins)
if table_joins.empty?
empty connection
else
aliases = Hash.new { |h,k|
h[k] = initial_count_for(connection, k, table_joins)
}
new connection, aliases
end
end
def self.initial_count_for(connection, name, table_joins)
# quoted_name should be downcased as some database adapters (Oracle) return quoted name in uppercase
quoted_name = connection.quote_table_name(name).downcase
counts = table_joins.map do |join|
if join.is_a?(Arel::Nodes::StringJoin)
# Table names + table aliases
join.left.downcase.scan(
/join(?:\s+\w+)?\s+(\S+\s+)?#{quoted_name}\son/
).size
else
join.left.table_name == name ? 1 : 0
end
end
counts.sum
end
# table_joins is an array of arel joins which might conflict with the aliases we assign here
def initialize(connection, aliases)
@aliases = aliases
@connection = connection
end
def aliased_table_for(table_name, aliased_name)
table_alias = aliased_name_for(table_name, aliased_name)
if table_alias == table_name
Arel::Table.new(table_name)
else
Arel::Table.new(table_name).alias(table_alias)
end
end
def aliased_name_for(table_name, aliased_name)
if aliases[table_name].zero?
# If it's zero, we can have our table_name
aliases[table_name] = 1
table_name
else
# Otherwise, we need to use an alias
aliased_name = connection.table_alias_for(aliased_name)
# Update the count
aliases[aliased_name] += 1
if aliases[aliased_name] > 1
"#{truncate(aliased_name)}_#{aliases[aliased_name]}"
else
aliased_name
end
end
end
private
def truncate(name)
name.slice(0, connection.table_alias_length - 2)
end
end
end
end
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