Timeout and Cancel

Per-command timeout

Each NzCommand supports a CommandTimeout property (in seconds). If the query does not complete within the timeout, the driver cancels the query and throws NetezzaException with a timeout message.

using var cmd = conn.CreateCommand("SELECT * FROM heavy_query");
cmd.CommandTimeout = 10; // seconds
try
{
    await using var reader = await cmd.ExecuteReaderAsync();
    while (await reader.ReadAsync())
        Process(reader);
}
catch (NetezzaException ex) when (ex.Message.Contains("timeout", StringComparison.OrdinalIgnoreCase))
{
    Console.WriteLine("Query timed out after 10 seconds");
}

Per-connection default timeout

Set a default timeout for all commands created from a connection:

connection.DefaultCommandTimeout = TimeSpan.FromSeconds(30);

// Commands inherit the connection's default
using var cmd1 = conn.CreateCommand("SELECT 1");
Console.WriteLine(cmd1.CommandTimeout); // 30

// Per-command override still works
cmd1.CommandTimeout = 5;

If DefaultCommandTimeout is not set explicitly, the default is 60 seconds. A timeout of 0 means "no timeout".

CancellationToken

All async methods accept CancellationToken for cooperative cancellation:

using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));
await using var reader = await cmd.ExecuteReaderAsync(cts.Token);
while (await reader.ReadAsync(cts.Token))
{
    // process
}

Connection-level cancel

To cancel a running query without disposing the connection:

connection.CancelQuery();

This sends a cancel request to the Netezza server. The connection remains open and can be used for subsequent queries.

How timeout works

1. A CancellationTokenSource is created with the CommandTimeout value
2. On timeout, the cancellation token is triggered
3. The driver sends a cancel request to the server
4. NetezzaException is thrown to the caller
5. The connection remains usable (not closed)

Best practices

• For interactive applications, use CancellationToken from the UI layer
• For batch processing, set CommandTimeout to a reasonable value for your workload
• A timeout of 0 means "no timeout" (wait indefinitely)
• Timeouts that are too short can cause false positives on slow queries
• Timeouts that are too long can leave connections blocked
• Handle timeout failures as NetezzaException