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$LOAD_PATH.unshift File.dirname(__FILE__) + '/..'
require 'tsort'
require 'rubyrep'
module RR
# This class sorts a given list of tables so that tables referencing other
# tables via foreign keys are placed behind those referenced tables.
#
# Rationale:
# If tables are sorted in that sequence, the risk of foreign key violations is
# smaller.
class TableSorter
include TSort
# The active +Session+
attr_accessor :session
# The list of table names to be ordered
attr_accessor :tables
# The table dependencies.
# Format as described e. g. here: PostgreSQLExtender#referenced_tables
def referenced_tables
unless @referenced_tables
@referenced_tables = session.left.referenced_tables(tables)
# Strip away all unrelated tables
@referenced_tables.each_pair do |table, references|
references.delete_if do |reference|
not tables.include? reference
end
end
end
@referenced_tables
end
# Yields each table.
# For details see standard library: TSort#sort_each_node.
def tsort_each_node
referenced_tables.each_key do |table|
yield table
end
end
# Yields all tables that are references by +table+.
def tsort_each_child(table)
referenced_tables[table].each do |reference|
yield reference
end
end
def sort
# Note:
# We should not use TSort#tsort as this one throws an exception if
# there are cyclic redundancies.
# (Our goal is to just get the best ordering that is possible and then
# take our chances.)
strongly_connected_components.flatten
end
# Initializes the TableSorter
# * session: The active +Session+ instance
# * tables: an array of table names
def initialize(session, tables)
self.session = session
self.tables = tables
end
end
end
Version data entries
17 entries across 17 versions & 2 rubygems