if is_in_transaction == 0 and
　　packet:byte() == proxy.COM_QUERY and
　　packet:sub(2, 7) == "SELECT" then
　　local max_conns = -1
　　local max_conns_ndx = 0
　　for i = 1, #proxy.servers do
　　local s = proxy.servers[i]
　　-- 需要選擇一個擁有空閑連接的從數(shù)據(jù)庫
　　if s.type == proxy.BACKEND_TYPE_RO and
　　s.idling_connections > 0 then
　　if max_conns == -1 or
　　s.connected_clients < max_conns then
　　max_conns = s.connected_clients
　　max_conns_ndx = i
　　end
　　end
　　end
　　-- 至此,我們找到了一個擁有空閑連接的從數(shù)據(jù)庫
　　if max_conns_ndx > 0 then
　　proxy.connection.backend_ndx = max_conns_ndx
　　end
　　else
　　-- 發(fā)送到主數(shù)據(jù)庫
　　end
　　return proxy.PROXY_SEND_QUERY