presto-main/src/main/java/io/prestosql/execution/DropTableTask.java/DropTableTask/execute
class DropTableTask:    @Override
    public ListenableFuture<?> execute(DropTable statement, TransactionManager transactionManager, Metadata metadata, AccessControl accessControl, QueryStateMachine stateMachine, List<Expression> parameters)
    {
        Session session = stateMachine.getSession();
        QualifiedObjectName tableName = createQualifiedObjectName(session, statement, statement.getTableName());

        Optional<TableHandle> tableHandle = metadata.getTableHandle(session, tableName);
        if (!tableHandle.isPresent()) {
            if (!statement.isExists()) {
                throw semanticException(TABLE_NOT_FOUND, statement, "Table '%s' does not exist", tableName);
            }
            return immediateFuture(null);
        }

        accessControl.checkCanDropTable(session.toSecurityContext(), tableName);

        metadata.dropTable(session, tableHandle.get());

        return immediateFuture(null);
    }