Get a (singular) name preorder record outstanding at the given block, given the preorder hash.
    NOTE: returns expired preorders.
    
    Return the preorder record on success.
    Return None if not found.

def namedb_get_name_preorder( db, preorder_hash, current_block ):
    """
    Get a (singular) name preorder record outstanding at the given block, given the preorder hash.
    NOTE: returns expired preorders.
    
    Return the preorder record on success.
    Return None if not found.
    """

    select_query = "SELECT * FROM preorders WHERE preorder_hash = ? AND op = ? AND block_number < ?;"
    args = (preorder_hash, NAME_PREORDER, current_block + NAME_PREORDER_EXPIRE)

    cur = db.cursor()
    preorder_rows = namedb_query_execute( cur, select_query, args )
    
    preorder_row = preorder_rows.fetchone()
    if preorder_row is None:
        # no such preorder 
        return None 

    preorder_rec = {}
    preorder_rec.update( preorder_row )

    unexpired_query, unexpired_args = namedb_select_where_unexpired_names( current_block )

    # make sure that the name doesn't already exist 
    select_query = "SELECT name_records.preorder_hash " + \
                   "FROM name_records JOIN namespaces ON name_records.namespace_id = namespaces.namespace_id " + \
                   "WHERE name_records.preorder_hash = ? AND " + \
                   unexpired_query + ";"

    args = (preorder_hash,) + unexpired_args
    
    cur = db.cursor()
    nm_rows = namedb_query_execute( cur, select_query, args )

    nm_row = nm_rows.fetchone()
    if nm_row is not None:
        # name with this preorder exists 
        return None 

    return preorder_rec