discourse/lib/column_dropper.rb

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class ColumnDropper
2017-05-04 13:41:05 -04:00
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
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