debian-mirror-gitlab/lib/gitlab/database/migration_helpers/v2.rb

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2021-03-11 19:13:27 +05:30
# frozen_string_literal: true
module Gitlab
module Database
module MigrationHelpers
module V2
include Gitlab::Database::MigrationHelpers
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# Superseded by `create_table` override below
def create_table_with_constraints(*_)
raise <<~EOM
#create_table_with_constraints is not supported anymore - use #create_table instead, for example:
create_table :db_guides do |t|
t.bigint :stars, default: 0, null: false
t.text :title, limit: 128
t.text :notes, limit: 1024
t.check_constraint 'stars > 1000', name: 'so_many_stars'
end
See https://docs.gitlab.com/ee/development/database/strings_and_the_text_data_type.html
EOM
end
# Creates a new table, optionally allowing the caller to add text limit constraints to the table.
# This method only extends Rails' `create_table` method
#
# Example:
#
# create_table :db_guides do |t|
# t.bigint :stars, default: 0, null: false
# t.text :title, limit: 128
# t.text :notes, limit: 1024
#
# t.check_constraint 'stars > 1000', name: 'so_many_stars'
# end
#
# See Rails' `create_table` for more info on the available arguments.
#
# When adding foreign keys to other tables, consider wrapping the call into a with_lock_retries block
# to avoid traffic stalls.
def create_table(table_name, *args, **kwargs, &block)
helper_context = self
super do |t|
t.define_singleton_method(:text) do |column_name, **kwargs|
limit = kwargs.delete(:limit)
super(column_name, **kwargs)
if limit
# rubocop:disable GitlabSecurity/PublicSend
name = helper_context.send(:text_limit_name, table_name, column_name)
# rubocop:enable GitlabSecurity/PublicSend
column_name = helper_context.quote_column_name(column_name)
definition = "char_length(#{column_name}) <= #{limit}"
t.check_constraint(definition, name: name)
end
end
t.instance_eval(&block) unless block.nil?
end
end
# Executes the block with a retry mechanism that alters the +lock_timeout+ and +sleep_time+ between attempts.
# The timings can be controlled via the +timing_configuration+ parameter.
# If the lock was not acquired within the retry period, a last attempt is made without using +lock_timeout+.
#
# In order to retry the block, the method wraps the block into a transaction.
#
# When called inside an open transaction it will execute the block directly if lock retries are enabled
# with `enable_lock_retries!` at migration level, otherwise it will raise an error.
#
# ==== Examples
# # Invoking without parameters
# with_lock_retries do
# drop_table :my_table
# end
#
# # Invoking with custom +timing_configuration+
# t = [
# [1.second, 1.second],
# [2.seconds, 2.seconds]
# ]
#
# with_lock_retries(timing_configuration: t) do
# drop_table :my_table # this will be retried twice
# end
#
# # Disabling the retries using an environment variable
# > export DISABLE_LOCK_RETRIES=true
#
# with_lock_retries do
# drop_table :my_table # one invocation, it will not retry at all
# end
#
# ==== Parameters
# * +timing_configuration+ - [[ActiveSupport::Duration, ActiveSupport::Duration], ...] lock timeout for the block, sleep time before the next iteration, defaults to `Gitlab::Database::WithLockRetries::DEFAULT_TIMING_CONFIGURATION`
# * +logger+ - [Gitlab::JsonLogger]
# * +env+ - [Hash] custom environment hash, see the example with `DISABLE_LOCK_RETRIES`
def with_lock_retries(*args, **kwargs, &block)
if transaction_open?
if enable_lock_retries?
Gitlab::AppLogger.warn 'Lock retries already enabled, executing the block directly'
yield
else
raise <<~EOF
#{__callee__} can not be run inside an already open transaction
Use migration-level lock retries instead, see https://docs.gitlab.com/ee/development/migration_style_guide.html#retry-mechanism-when-acquiring-database-locks
EOF
end
else
super(*args, **kwargs.merge(allow_savepoints: false), &block)
end
end
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# 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