debian-mirror-gitlab/lib/gitlab/database/migration_helpers/v2.rb
2021-03-11 19:13:27 +05:30

219 lines
8.4 KiB
Ruby

# frozen_string_literal: true
module Gitlab
module Database
module MigrationHelpers
module V2
include Gitlab::Database::MigrationHelpers
# Renames a column without requiring downtime.
#
# Concurrent renames work by using database triggers to ensure both the
# old and new column are in sync. However, this method will _not_ remove
# the triggers or the old column automatically; this needs to be done
# manually in a post-deployment migration. This can be done using the
# method `cleanup_concurrent_column_rename`.
#
# table - The name of the database table containing the column.
# old_column - The old column name.
# new_column - The new column name.
# type - The type of the new column. If no type is given the old column's
# type is used.
# batch_column_name - option is for tables without primary key, in this
# case another unique integer column can be used. Example: :user_id
def rename_column_concurrently(table, old_column, new_column, type: nil, batch_column_name: :id)
setup_renamed_column(__callee__, table, old_column, new_column, type, batch_column_name)
with_lock_retries do
install_bidirectional_triggers(table, old_column, new_column)
end
end
# Reverses operations performed by rename_column_concurrently.
#
# This method takes care of removing previously installed triggers as well
# as removing the new column.
#
# table - The name of the database table.
# old_column - The name of the old column.
# new_column - The name of the new column.
def undo_rename_column_concurrently(table, old_column, new_column)
teardown_rename_mechanism(table, old_column, new_column, column_to_remove: new_column)
end
# Cleans up a concurrent column name.
#
# This method takes care of removing previously installed triggers as well
# as removing the old column.
#
# table - The name of the database table.
# old_column - The name of the old column.
# new_column - The name of the new column.
def cleanup_concurrent_column_rename(table, old_column, new_column)
teardown_rename_mechanism(table, old_column, new_column, column_to_remove: old_column)
end
# Reverses the operations performed by cleanup_concurrent_column_rename.
#
# This method adds back the old_column removed
# by cleanup_concurrent_column_rename.
# It also adds back the triggers that are removed
# by cleanup_concurrent_column_rename.
#
# table - The name of the database table containing the column.
# old_column - The old column name.
# new_column - The new column name.
# type - The type of the old column. If no type is given the new column's
# type is used.
# batch_column_name - option is for tables without primary key, in this
# case another unique integer column can be used. Example: :user_id
#
def undo_cleanup_concurrent_column_rename(table, old_column, new_column, type: nil, batch_column_name: :id)
setup_renamed_column(__callee__, table, new_column, old_column, type, batch_column_name)
with_lock_retries do
install_bidirectional_triggers(table, old_column, new_column)
end
end
private
def setup_renamed_column(calling_operation, table, old_column, new_column, type, batch_column_name)
if transaction_open?
raise "#{calling_operation} can not be run inside a transaction"
end
column = columns(table).find { |column| column.name == old_column.to_s }
unless column
raise "Column #{old_column} does not exist on #{table}"
end
if column.default
raise "#{calling_operation} does not currently support columns with default values"
end
unless column_exists?(table, batch_column_name)
raise "Column #{batch_column_name} does not exist on #{table}"
end
check_trigger_permissions!(table)
unless column_exists?(table, new_column)
create_column_from(table, old_column, new_column, type: type, batch_column_name: batch_column_name)
end
end
def teardown_rename_mechanism(table, old_column, new_column, column_to_remove:)
return unless column_exists?(table, column_to_remove)
with_lock_retries do
check_trigger_permissions!(table)
remove_bidirectional_triggers(table, old_column, new_column)
remove_column(table, column_to_remove)
end
end
def install_bidirectional_triggers(table, old_column, new_column)
insert_trigger_name, update_old_trigger_name, update_new_trigger_name =
bidirectional_trigger_names(table, old_column, new_column)
quoted_table = quote_table_name(table)
quoted_old = quote_column_name(old_column)
quoted_new = quote_column_name(new_column)
create_insert_trigger(insert_trigger_name, quoted_table, quoted_old, quoted_new)
create_update_trigger(update_old_trigger_name, quoted_table, quoted_new, quoted_old)
create_update_trigger(update_new_trigger_name, quoted_table, quoted_old, quoted_new)
end
def remove_bidirectional_triggers(table, old_column, new_column)
insert_trigger_name, update_old_trigger_name, update_new_trigger_name =
bidirectional_trigger_names(table, old_column, new_column)
quoted_table = quote_table_name(table)
drop_trigger(insert_trigger_name, quoted_table)
drop_trigger(update_old_trigger_name, quoted_table)
drop_trigger(update_new_trigger_name, quoted_table)
end
def bidirectional_trigger_names(table, old_column, new_column)
%w[insert update_old update_new].map do |operation|
'trigger_' + Digest::SHA256.hexdigest("#{table}_#{old_column}_#{new_column}_#{operation}").first(12)
end
end
def function_name_for_trigger(trigger_name)
"function_for_#{trigger_name}"
end
def create_insert_trigger(trigger_name, quoted_table, quoted_old_column, quoted_new_column)
function_name = function_name_for_trigger(trigger_name)
execute(<<~SQL)
CREATE OR REPLACE FUNCTION #{function_name}()
RETURNS trigger
LANGUAGE plpgsql
AS $$
BEGIN
IF NEW.#{quoted_old_column} IS NULL AND NEW.#{quoted_new_column} IS NOT NULL THEN
NEW.#{quoted_old_column} = NEW.#{quoted_new_column};
END IF;
IF NEW.#{quoted_new_column} IS NULL AND NEW.#{quoted_old_column} IS NOT NULL THEN
NEW.#{quoted_new_column} = NEW.#{quoted_old_column};
END IF;
RETURN NEW;
END
$$;
DROP TRIGGER IF EXISTS #{trigger_name}
ON #{quoted_table};
CREATE TRIGGER #{trigger_name}
BEFORE INSERT ON #{quoted_table}
FOR EACH ROW EXECUTE FUNCTION #{function_name}();
SQL
end
def create_update_trigger(trigger_name, quoted_table, quoted_source_column, quoted_target_column)
function_name = function_name_for_trigger(trigger_name)
execute(<<~SQL)
CREATE OR REPLACE FUNCTION #{function_name}()
RETURNS trigger
LANGUAGE plpgsql
AS $$
BEGIN
NEW.#{quoted_target_column} := NEW.#{quoted_source_column};
RETURN NEW;
END
$$;
DROP TRIGGER IF EXISTS #{trigger_name}
ON #{quoted_table};
CREATE TRIGGER #{trigger_name}
BEFORE UPDATE OF #{quoted_source_column} ON #{quoted_table}
FOR EACH ROW EXECUTE FUNCTION #{function_name}();
SQL
end
def drop_trigger(trigger_name, quoted_table)
function_name = function_name_for_trigger(trigger_name)
execute(<<~SQL)
DROP TRIGGER IF EXISTS #{trigger_name}
ON #{quoted_table};
DROP FUNCTION IF EXISTS #{function_name};
SQL
end
end
end
end
end