Merge pull request #11 from freshworks/v2-lhm-trigger-drop-on-migrati…

…on-fix

[FD-120307] : LHM Trigger Drop Fix

lib/lhm/connection.rb

@@ -142,6 +142,15 @@ def execute(sql)
  def table_exists?(table_name)
  @adapter.table_exists?(table_name)
  end
+
+ def trigger_exists?(table_name, trigger_name)
+ !!select_one(%Q{
+ select trigger_name
+ from information_schema.triggers
+ where event_object_table='#{table_name}'
+ and trigger_name like '#{trigger_name}'
+ })
+ end
  end
  end
 end

lib/lhm/invoker.rb

@@ -6,6 +6,7 @@
 require 'lhm/atomic_switcher'
 require 'lhm/locked_switcher'
 require 'lhm/migrator'
+require 'lhm/trigger_switcher'
 
 module Lhm
  # Copies an origin table to an altered destination table. Live activity is
@@ -16,9 +17,10 @@ module Lhm
  class Invoker
  include SqlHelper
 
- attr_reader :migrator, :connection
+ attr_reader :migrator, :connection, :origin
 
  def initialize(origin, connection)
+ @origin = origin
  @connection = connection
  @migrator = Migrator.new(origin, connection)
  end
@@ -40,8 +42,9 @@ def run(options = {})
  Chunker.new(migration, @connection, options).run
  if options[:atomic_switch]
  AtomicSwitcher.new(migration, @connection).run
+ TriggerSwitcher.new.copy_triggers(@origin, migration.archive_name, @connection) if options[:retain_triggers]
  else
- LockedSwitcher.new(migration, @connection).run
+ LockedSwitcher.new(migration, @connection, options[:retain_triggers]).run
  end
  end
  end

lib/lhm/locked_switcher.rb

@@ -4,6 +4,7 @@
 require 'lhm/command'
 require 'lhm/migration'
 require 'lhm/sql_helper'
+require 'lhm/trigger_switcher'
 
 module Lhm
  # Switches origin with destination table nonatomically using a locked write.
@@ -22,25 +23,38 @@ class LockedSwitcher
 
  attr_reader :connection
 
- def initialize(migration, connection = nil)
+ def initialize(migration, connection = nil, retain_triggers = false)
  @migration = migration
  @connection = connection
  @origin = migration.origin
  @destination = migration.destination
+ @retain_triggers = retain_triggers
  end
 
  def statements
  uncommitted { switch }
  end
 
  def switch
- [
+ queries = [
  "lock table `#{ @origin.name }` write, `#{ @destination.name }` write",
  "alter table `#{ @origin.name }` rename `#{ @migration.archive_name }`",
  "alter table `#{ @destination.name }` rename `#{ @origin.name }`",
  "commit",
  "unlock tables"
  ]
+ if @retain_triggers
+ trigger_copy_queries = []
+ trigger_copy_queries << "lock table `#{ @migration.archive_name }` write, `#{ @origin.name }` write"
+ @origin.triggers.each do |trigger|
+ trigger_name = trigger[0]
+ trigger_copy_queries << "DROP TRIGGER #{trigger_name};"
+ trigger_copy_queries << TriggerSwitcher.new.fetch_trigger_definition(trigger_name, connection)
+ end
+ target_index = queries.index('commit')
+ queries.insert(target_index, *trigger_copy_queries) if trigger_copy_queries.length > 0 # inserting the trigger queries before commit query
+ end
+ queries
  end
 
  def uncommitted(&block)

lib/lhm/table.rb

@@ -6,11 +6,13 @@
 module Lhm
  class Table
  attr_reader :name, :columns, :indices, :pk, :ddl
+ attr_accessor :triggers
 
  def initialize(name, pk = "id", ddl = nil)
  @name = name
  @columns = {}
  @indices = {}
+ @triggers = []
  @pk = valid_primary_key(pk)
  @ddl = ddl
  end
@@ -69,11 +71,18 @@ def parse
  extract_indices(read_indices).each do |idx, columns|
  table.indices[idx] = columns
  end
+
+ table.triggers = read_triggers
  end
  end
 
  private
 
+ def read_triggers
+ sql = "show triggers where `table`= '#{@table_name}';"
+ @connection.execute(sql)
+ end
+
  def read_information_schema
  @connection.select_all %Q{
  select *

lib/lhm/trigger_switcher.rb

@@ -0,0 +1,36 @@
+module Lhm
+ class TriggerSwitcher
+ def copy_triggers(source_table, destination_table_name, connection)
+ return unless !destination_table_name.empty? && connection.table_exists?(destination_table_name)
+
+ source_table.triggers.each do |trigger|
+ trigger_name = trigger[0]
+ trigger_definition = fetch_trigger_definition(trigger_name, connection)
+ # since source table is renamed to lhma_table_name(destination table name) after migration, triggers associated with the source table will now be associated with lhma_table_name.
+ # skip if the trigger isn't associated with lhma_table_name.
+ next unless trigger_definition.include? destination_table_name
+
+ old_trigger_name = trigger_name
+ trigger_name = remove_timestamp_from_trigger_name_if_exists(trigger_name)
+ modified_trigger_name = trigger_name + '_' + Time.now.getutc.to_s.gsub(/[:\- ]/, '_') #sample trigger name - trigger_name_2023_12_18_03_40_45_UTC
+ modified_definition = trigger_definition.gsub(destination_table_name, source_table.name)
+ modified_definition = modified_definition.gsub(old_trigger_name, modified_trigger_name)
+ connection.execute(modified_definition)
+ connection.execute("DROP TRIGGER #{old_trigger_name};")
+ end
+ end
+
+ def fetch_trigger_definition(trigger_name, connection)
+ result = connection.execute("SHOW CREATE TRIGGER #{trigger_name};").first
+ # sample result => ["update_message_old_5", "NO_ENGINE_SUBSTITUTION", "CREATE DEFINER=`root`@`localhost` TRIGGER update_message_old_5 BEFORE INSERT ON `lhma_2023_09_04_14_32_54_810_logs_table` FOR EACH ROW\n BEGIN\n IF NEW.message = '1' THEN\n SET NEW.message = 'true';\n END IF;\n END", "utf8", "utf8_general_ci", "utf8_unicode_ci", 2023-09-04 14:32:43 UTC]
+ # create trigger definition will be stored in the third index in the result, ideally result will always be of length 7 if its executed successfully.
+ result && result.length > 2 ? result[2] : ''
+ end
+
+ def remove_timestamp_from_trigger_name_if_exists(trigger_name)
+ timestamp_suffix_regex = /_(\d{4}_\d{2}_\d{2}_\d{2}_\d{2}_\d{2}_UTC)\z/
+ match_data = trigger_name.match(/^(.*?)(?:#{timestamp_suffix_regex})$/)
+ match_data ? match_data[1] : trigger_name
+ end
+ end
+end

spec/integration/integration_helper.rb

@@ -124,6 +124,22 @@ def table_exists?(table)
  connection.table_exists?(table.name)
  end
 
+ def trigger_exists?(table_name, trigger_name)
+ connection.trigger_exists?(table_name, trigger_name)
+ end
+
+ def check_and_create_trigger_on_users_table
+ table_name = 'users'
+ trigger_name = 'timestamp_trigger'
+ unless trigger_exists?(table_name, trigger_name)
+ query = "CREATE TRIGGER #{trigger_name} BEFORE INSERT ON #{table_name} FOR EACH ROW
+ BEGIN
+ SET NEW.created_at = NOW();
+ END;"
+ execute query
+ end
+ end
+
  #
  # Database Helpers
  #

spec/integration/lhm_spec.rb

@@ -29,6 +29,59 @@
  end
  end
 
+ it "should retain triggers while migration if retain_triggers is set to true in atomic switch" do
+ table_name = 'users'
+ trigger_name = 'timestamp_trigger'
+ check_and_create_trigger_on_users_table
+ Lhm.change_table(table_name.to_sym, :atomic_switch => true, :cleanup => true, :retain_triggers => true) do |t|
+ t.add_column(:logins, "INT(12) DEFAULT '0'")
+ end
+
+ slave do
+ trigger_exists?(table_name, trigger_name).must_equal true
+ end
+ end
+
+ it "should retain triggers while migration if retain_triggers is set to true in locked switch" do
+ table_name = 'users'
+ trigger_name = 'timestamp_trigger'
+ check_and_create_trigger_on_users_table
+ Lhm.change_table(table_name.to_sym, :atomic_switch => false, :cleanup => true, :retain_triggers => true) do |t|
+ t.add_column(:logins, "INT(12) DEFAULT '0'")
+ end
+
+ slave do
+ trigger_exists?(table_name, trigger_name).must_equal true
+ end
+ end
+
+ it "should not retain triggers while migration if retain_triggers is set to false" do
+ table_name = 'users'
+ trigger_name = 'timestamp_trigger'
+ check_and_create_trigger_on_users_table
+ Lhm.change_table(table_name.to_sym, :atomic_switch => false, :cleanup => true, :retain_triggers => false) do |t|
+ t.add_column(:logins_1, "INT(12) DEFAULT '0'")
+ end
+
+ slave do
+ trigger_exists?(table_name, trigger_name).must_equal false
+ end
+ end
+
+ it "should not retain triggers while migration if retain_triggers is not passed in the options" do
+ table_name = 'users'
+ trigger_name = 'timestamp_trigger'
+ check_and_create_trigger_on_users_table
+ Lhm.change_table(table_name.to_sym, :atomic_switch => false, :cleanup => true) do |t|
+ t.add_column(:logins_2, "INT(12) DEFAULT '0'")
+ end
+
+ slave do
+ trigger_exists?(table_name, trigger_name).must_equal false
+ end
+ end
+
+
  it "should copy all rows" do
  23.times { |n| execute("insert into users set reference = '#{ n }'") }