class ColumnDropper def self.drop(table:, after_migration:, columns:, delay: nil, on_drop: nil) raise ArgumentError.new("Invalid table name passed to drop #{table}") if table =~ /[^a-z0-9_]/i columns.each do |column| raise ArgumentError.new("Invalid column name passed to drop #{column}") if column =~ /[^a-z0-9_]/i end delay ||= Rails.env.production? ? 60 : 0 sql = <<~SQL SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS WHERE table_schema = 'public' AND table_name = :table AND column_name IN (:columns) AND EXISTS ( SELECT 1 FROM schema_migration_details WHERE name = :after_migration AND created_at <= (current_timestamp at time zone 'UTC' - interval :delay) ) LIMIT 1 SQL if ActiveRecord::Base.exec_sql(sql, table: table, columns: columns, delay: "#{delay.to_i || 0} seconds", after_migration: after_migration).to_a.length > 0 on_drop&.call columns.each do |column| # safe cause it is protected on method entry, can not be passed in params ActiveRecord::Base.exec_sql("ALTER TABLE #{table} DROP COLUMN IF EXISTS #{column}") ActiveRecord::Base.exec_sql <<~SQL DROP FUNCTION IF EXISTS #{readonly_function_name(table, column)}; DROP TRIGGER IF EXISTS #{readonly_trigger_name(table, column)} ON #{table}; SQL end Discourse.reset_active_record_cache end end def self.mark_readonly(table_name, column_name) ActiveRecord::Base.exec_sql <<-SQL CREATE OR REPLACE FUNCTION #{readonly_function_name(table_name, column_name)} RETURNS trigger AS $rcr$ BEGIN RAISE EXCEPTION 'Discourse: #{column_name} in #{table_name} is readonly'; END $rcr$ LANGUAGE plpgsql; SQL ActiveRecord::Base.exec_sql <<-SQL CREATE TRIGGER #{readonly_trigger_name(table_name, column_name)} BEFORE INSERT OR UPDATE OF #{column_name} ON #{table_name} FOR EACH ROW WHEN (NEW.#{column_name} IS NOT NULL) EXECUTE PROCEDURE #{readonly_function_name(table_name, column_name)}; SQL end private def self.readonly_function_name(table_name, column_name) "raise_#{table_name}_#{column_name}_readonly()" end def self.readonly_trigger_name(table_name, column_name) "#{table_name}_#{column_name}_readonly" end end