[Seaside] Re: Scaling Seaside apps (was: About SToR)

[Colin Putney]

On Aug 5, 2006, at 11:28 AM, Yanni Chiu wrote:

> The protocol returns a row at a time until there no more (indicated
> by a CompletedResponse message, instead of another Row message). It  
> seems both Bruce and I chose to implement in such a way that a  
> result set is only available after the last row has been received.
>
> I suppose a better choice (for the future) would return with a
> result set stream as soon as the first row is retrieved. Then add
> additional protocol to return the entire result set by pulling in
> the whole stream contents.

Yeah, that's handy alright. The Squeak MySQL driver does this. The  
implementation in the MySQL driver has a significant flaw though, in  
that it basically relies on the client reading rows from the stream  
to cause the driver to read bytes from the socket. This leads to  
problems when the client fails to read all the rows that were  
returned. If there is an error and reading is curtailed, the user  
cancels the action or whatever, the row bytes are left in the socket  
buffer and the driver gets confused the next time it sends a query  
and receives unexpected results.

That's not to say that a result set stream is a bad idea, it just has  
to be implemented to so that the driver maintains control over  
reading from the socket and can keep a consistent state when the  
result stream isn't read completely.

Just a heads up - the problem can be hard to track down and has  
caused me lots of grief in the past.

Colin