Impala client fetch wait states

Impala client fetch wait states represent the period when the coordinator halts processing resources while waiting for a client application to retrieve query results.

The Waiting on client status indicates that the Impala coordinator is waiting for the client to fetch result rows. This status does not mean the query is actively running or consuming processing resources on the daemons. Instead, the coordinator keeps the session open until the client fetches all data or the session times out.

An extended wait status occurs due to the following operational factors:

• Slow client data retrieval - Client applications running by using the ODBC driver or the JDBC driver frequently fetch data slower than the network or coordinator can deliver it.
• High-volume result sets - Data operations that return millions of rows create significant latency when you download rows locally over a bottlenecked network.