cmd.Cancel() in QueryRowImpl finally block causes ORA-1013 on Oracle Database Queries

Summary

The finally block in QueryRowImpl<T> calls cmd.Cancel() when the reader is not null and not closed. While this works safely with SQL Server, it causes Oracle to raise ORA-1013 ("user requested cancel of current operation") on any non-happy-path exit from the method.

Affected Method

SqlMapper.cs → QueryRowImpl<T>

finally
{
    if (reader is not null)
    {
        if (!reader.IsClosed)
        {
            try { cmd?.Cancel(); }
            catch { /* don't spoil any existing exception */ }
        }
        reader.Dispose();
    }
    if (wasClosed) cnn.Close();
    cmd?.Parameters.Clear();
    cmd?.Dispose();
}

Root Cause

cmd.Cancel() is reached whenever reader is not disposed before the finally block. This happens on all non-happy paths, including:

On SQL Server, cmd.Cancel() is a safe and common cleanup pattern.
On Oracle (ODP.NET / Oracle.ManagedDataAccess), it sends an explicit cancel signal to the server, which raises ORA-1013 as a hard error — masking the original exception (e.g. "no rows found", "multiple rows", or a query error).

Behaviour Discrepancy

• SQL Server: cmd.Cancel() → silently acknowledged, resources released
• Oracle: cmd.Cancel() → raises ORA-1013, surfaces as an unrelated error in the application

Workaround

Commenting out the cmd.Cancel() call resolves the issue. reader.Dispose() alone is sufficient for cleanup on Oracle — the explicit cancel is unnecessary and harmful.

Suggested Fix

Consider making the cancel behaviour conditional on the provider, or removing it entirely since reader.Dispose() already handles cleanup across all major providers:

//if (!reader.IsClosed)
//{
    // cmd.Cancel() triggers ORA-1013 on Oracle (see issue #XXXX).
    // reader.Dispose() below is sufficient for cleanup across providers.
    // try { cmd?.Cancel(); }
    // catch { /* don't spoil any existing exception */ }
//}

Though the provider-agnostic approach (simply removing the call) is cleaner since Dispose() is sufficient.

Environment

• Dapper version: latest (main branch)
• Oracle driver: Oracle.ManagedDataAccess.Core
• .NET version: .NET 10
• Database: Oracle

References

• Oracle ORA-1013: https://docs.oracle.com/error-help/db/ora-01013/