Interrupt handling

[mkaruza]

• Declare QuackNode to HOLD_INTERRUPTS for duration of scan. Once interrupt is observed we exit execution after heap pages are closed.

[hlinnaka]

Note that most postgres internal functions can ereport an error for a wide range of reasons, so the code needs to be prepared for that anyway regardless of interrupts.

[mkaruza]

Note that most postgres internal functions can ereport an error for a wide range of reasons, so the code needs to be prepared for that anyway regardless of interrupts.

@hlinnaka You are by right looking at PG code. This interrupt PR is mostly for safer cleaning and closing all pages during query execution. You think that this should be checking specific - QueryCancelPending variable and/or increasing QueryCancelHoldoffCount counter.

[Mytherin]

We can call Interrupt on the DuckDB Connection object to interrupt the running DuckDB query as well, that should allow us to interrupt during e.g. Parquet readers and other operations.

We could launch a background thread that polls periodically whether or not a cancellation has happened, when it has happened we call Interrupt.

[Mytherin]

We could in the future e.g. have a background thread here:

void CheckForInterrupts() {
    while(!finished) {
        if (QueryCancelPending) {
               connection->Interrupt();
               break;
        }
        sleep(10ms);
    }
}