Add support for tables with multiple outbound foreign key constraints

Author: Romain Pomier

lib/lhm/migrator.rb

@@ -207,9 +207,7 @@ def execute
     end
 
     def destination_create
-      original    = %{CREATE TABLE `#{ @origin.name }`}
-      replacement = %{CREATE TABLE `#{ @origin.destination_name }`}
-      stmt = @origin.ddl.gsub(original, replacement)
+      stmt = @origin.destination_ddl
       @connection.execute(tagged(stmt))
     end
 

lib/lhm/table.rb

@@ -5,12 +5,14 @@
 
 module Lhm
   class Table
-    attr_reader :name, :columns, :indices, :pk, :ddl
+    attr_reader :schema, :name, :columns, :indices, :constraints, :pk, :ddl
 
-    def initialize(name, pk = 'id', ddl = nil)
+    def initialize(name, schema = 'default', pk = 'id', ddl = nil)
       @name = name
+      @schema = schema
       @columns = {}
       @indices = {}
+      @constraints = {}
       @pk = pk
       @ddl = ddl
     end
@@ -28,6 +30,32 @@ def self.parse(table_name, connection)
       Parser.new(table_name, connection).parse
     end
 
+    def destination_ddl
+      original    = %r{CREATE TABLE ("|`)#{ name }\1}
+      repl = '\1'
+      replacement = %Q{CREATE TABLE #{ repl }#{ destination_name }#{ repl }}
+
+      dest = ddl
+      dest.gsub!(original, replacement)
+
+      foreign_keys = constraints.select { |col, c| !c[:referenced_column].nil? }
+
+      foreign_keys.keys.each_with_index do |key, i|
+        original = foreign_keys[key][:name]
+        replacement = replacement_constraint(original)
+        dest.gsub!(original, replacement)
+      end
+
+      dest
+    end
+
+    @@schema_constraints = {}
+
+    def self.schema_constraints(schema, value = nil)
+      @@schema_constraints[schema] = value if value
+      @@schema_constraints[schema]
+    end
+
     class Parser
       include SqlHelper
 
@@ -47,7 +75,7 @@ def ddl
       def parse
         schema = read_information_schema
 
-        Table.new(@table_name, extract_primary_key(schema), ddl).tap do |table|
+        Table.new(@table_name, @schema_name, extract_primary_key(schema), ddl).tap do |table|
           schema.each do |defn|
             column_name    = struct_key(defn, 'COLUMN_NAME')
             column_type    = struct_key(defn, 'COLUMN_TYPE')
@@ -64,6 +92,15 @@ def parse
           extract_indices(read_indices).each do |idx, columns|
             table.indices[idx] = columns
           end
+
+          constraints = {}
+          extract_constraints(read_constraints(nil)).each do |data|
+            if data[:schema] == @schema_name && data[:table] == @table_name
+              table.constraints[data[:column]] = data
+            end
+            constraints[data[:name]] = data
+          end
+          Table.schema_constraints(@schema_name, constraints)
         end
       end
 
@@ -98,6 +135,47 @@ def extract_indices(indices)
           end
       end
 
+      def read_constraints(table = @table_name)
+        query = %Q{
+          select *
+            from information_schema.key_column_usage
+           where table_schema = '#{ @schema_name }'
+             and referenced_column_name is not null
+        }
+        query += %Q{
+             and table_name = '#{ @table_name }'
+        } if table
+
+        @connection.select_all(query)
+      end
+
+      def extract_constraints(constraints)
+        columns = %w{
+          CONSTRAINT_NAME
+          TABLE_SCHEMA
+          TABLE_NAME
+          COLUMN_NAME
+          ORDINAL_POSITION
+          POSITION_IN_UNIQUE_CONSTRAINT
+          REFERENCED_TABLE_SCHEMA
+          REFERENCED_TABLE_NAME
+          REFERENCED_COLUMN_NAME
+        }
+
+        constraints.map do |row|
+          result = {}
+          columns.each do |c|
+            sym = c.dup
+            # The order of these substitutions is important
+            sym.gsub!(/CONSTRAINT_/, '')
+            sym.gsub!(/_NAME/, '')
+            sym.gsub!(/TABLE_/, '')
+            result[sym.downcase.to_sym] = row[struct_key(row, c)]
+          end
+          result
+        end
+      end
+
       def extract_primary_key(schema)
         cols = schema.select do |defn|
           column_key = struct_key(defn, 'COLUMN_KEY')
@@ -112,5 +190,12 @@ def extract_primary_key(schema)
         keys.length == 1 ? keys.first : keys
       end
     end
+
+    private
+
+    def replacement_constraint(name)
+      (name =~ /_lhmn$/).nil? ? "#{name}_lhmn" : name.gsub(/_lhmn$/, '')
+    end
+
   end
 end

spec/fixtures/fk_example.ddl

@@ -0,0 +1,8 @@
+CREATE TABLE `fk_example` (
+  `id` int(11) NOT NULL AUTO_INCREMENT,
+  `user_id` int(11) NOT NULL,
+  `master_id` int(11) NOT NULL,
+  PRIMARY KEY (`id`),
+  CONSTRAINT `fk_example_ibfk_1` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`),
+  CONSTRAINT `fk_example_ibfk_2` FOREIGN KEY (`master_id`) REFERENCES `users` (`id`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8

spec/fixtures/fk_example_second_pass.ddl

@@ -0,0 +1,8 @@
+CREATE TABLE `fk_example_second_pass` (
+  `id` int(11) NOT NULL AUTO_INCREMENT,
+  `user_id` int(11) NOT NULL,
+  `master_id` int(11) NOT NULL,
+  PRIMARY KEY (`id`),
+  CONSTRAINT `fk_example_ibfk_1_lhmn` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`),
+  CONSTRAINT `fk_example_ibfk_2_lhmn` FOREIGN KEY (`master_id`) REFERENCES `users` (`id`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8

spec/integration/foreign_keys_spec.rb

@@ -0,0 +1,89 @@
+# Copyright (c) 2011 - 2013, SoundCloud Ltd., Rany Keddo, Tobias Bielohlawek, Tobias
+# Schmidt
+
+require File.expand_path(File.dirname(__FILE__)) + '/integration_helper'
+
+require 'lhm'
+
+describe Lhm do
+  include IntegrationHelper
+
+  before(:each) do
+    connect_master!
+    Lhm.cleanup(true)
+    %w(fk_example fk_example_second_pass).each do |table|
+      execute "drop table if exists #{table}"
+    end
+    table_create(:users)
+  end
+
+  describe 'the simplest case' do
+    before(:each) do
+      table_create(:fk_example)
+    end
+
+    after(:each) do
+      execute 'drop table if exists fk_example'
+      Lhm.cleanup(true)
+    end
+
+    it 'should handle tables with foreign keys by appending the suffix' do
+      Lhm.change_table(:fk_example) do |t|
+        t.add_column(:new_column, "INT(12) DEFAULT '0'")
+      end
+
+      slave do
+        actual = table_read(:fk_example).constraints['user_id']
+        expected = {
+          name: 'fk_example_ibfk_1_lhmn',
+          referenced_table: 'users',
+          referenced_column: 'id',
+        }
+        hash_slice(actual, expected.keys).must_equal(expected)
+
+        actual = table_read(:fk_example).constraints['master_id']
+        expected = {
+          name: 'fk_example_ibfk_2_lhmn',
+          referenced_table: 'users',
+          referenced_column: 'id',
+        }
+        hash_slice(actual, expected.keys).must_equal(expected)
+      end
+    end
+  end
+
+  describe 'manage a new migration by removing the suffix' do
+    before(:each) do
+      table_create(:fk_example_second_pass)
+    end
+
+    after(:each) do
+      execute 'drop table if exists fk_example_second_pass'
+      Lhm.cleanup(true)
+    end
+
+    it 'should be able to create this table' do
+      Lhm.change_table(:fk_example_second_pass) do |t|
+        t.add_column(:new_column, "INT(12) DEFAULT '0'")
+      end
+
+      slave do
+        actual = table_read(:fk_example_second_pass).constraints['user_id']
+        expected = {
+          name: 'fk_example_ibfk_1',
+          referenced_table: 'users',
+          referenced_column: 'id',
+        }
+        hash_slice(actual, expected.keys).must_equal(expected)
+
+        actual = table_read(:fk_example_second_pass).constraints['master_id']
+        expected = {
+          name: 'fk_example_ibfk_2',
+          referenced_table: 'users',
+          referenced_column: 'id',
+        }
+        hash_slice(actual, expected.keys).must_equal(expected)
+      end
+    end
+  end
+end

spec/integration/integration_helper.rb

@@ -125,6 +125,11 @@ def table_exists?(table)
     connection.table_exists?(table.name)
   end
 
+  def hash_slice(hash, keys)
+    return hash.slice(*keys) if hash.respond_to?(:slice)
+    keys.each { |k| [k, hash[k]] }.to_h
+  end
+
   #
   # Database Helpers
   #

spec/integration/table_spec.rb

@@ -86,6 +86,23 @@
           indices['index_users_on_reference'].
           must_equal(['reference'])
       end
+
+      it 'should parse constraints' do
+        begin
+          @table = table_create(:fk_example)
+          @table.constraints.keys.must_equal %w(user_id master_id)
+
+          expected = {
+            name: 'fk_example_ibfk_1',
+            referenced_table: 'users',
+            referenced_column: 'id'
+          }
+
+          hash_slice(@table.constraints['user_id'], expected.keys).must_equal expected
+        ensure
+          execute 'drop table if exists fk_example'
+        end
+      end
     end
   end
 end

spec/unit/table_spec.rb

@@ -15,25 +15,38 @@
     end
   end
 
+  describe 'ddl' do
+    it 'should build the destination table' do
+      table = 'users'
+      schema = 'default'
+
+      @table = Lhm::Table.new(table, schema, 'id', %Q{CREATE TABLE `#{table}` (random_constraint)})
+      @table.constraints['user_id'] = {:name => 'random_constraint', :referenced_column => true}
+      Lhm::Table.schema_constraints(schema, {'random_constraint_lhmn' => true})
+
+      @table.destination_ddl.must_equal %Q{CREATE TABLE `#{@table.destination_name}` (random_constraint_lhmn)}
+    end
+  end
+
   describe 'constraints' do
     def set_columns(table, columns)
       table.instance_variable_set('@columns', columns)
     end
 
     it 'should be satisfied with a single column primary key called id' do
-      @table = Lhm::Table.new('table', 'id')
+      @table = Lhm::Table.new('table', 'default', 'id')
       set_columns(@table, { 'id' => { :type => 'int(1)' } })
       @table.satisfies_id_column_requirement?.must_equal true
     end
 
     it 'should be satisfied with a primary key not called id, as long as there is still an id' do
-      @table = Lhm::Table.new('table', 'uuid')
+      @table = Lhm::Table.new('table', 'default', 'uuid')
       set_columns(@table, { 'id' => { :type => 'int(1)' } })
       @table.satisfies_id_column_requirement?.must_equal true
     end
 
     it 'should not be satisfied if id is not numeric' do
-      @table = Lhm::Table.new('table', 'id')
+      @table = Lhm::Table.new('table', 'default', 'id')
       set_columns(@table, { 'id' => { :type => 'varchar(255)' } })
       @table.satisfies_id_column_requirement?.must_equal false
     end