TCP has an "urgent data" feature that might have been used for this kind of thing, used for Ctrl-C in telnet, etc. It can be used to bypass any pending send buffer and received by the server ahead of any unread data.
michalc 58 minutes ago [-]
I think I can understand why this wasn’t addressed for so long: in the vast majority of cases if your db is exposed on a network level to untrusted sources, then you probably have far bigger problems?
jtwaleson 1 hours ago [-]
From the title I was hoping for this being hacky on the server application side, like how it aborts and clears the memory for a running query.
Still an interesting read. Just wondering, why can't the TCP connection of the query not be used to send a cancellation request? Why does it have the be out of band?
toast0 1 hours ago [-]
I don't know much about postgres, but as I understand it, it's a pretty standard server application. Read a request from the client, work on the request, send the result, read the next request.
Changing that to poll for a cancellation while working is a big change. Also, the server would need to buffer any pipelined requests while looking for a cancellation request. A second connection is not without wrinkles, but it avoids a lot of network complexity.
bob1029 1 hours ago [-]
MSSQL uses a special message over an existing connection:
Still an interesting read. Just wondering, why can't the TCP connection of the query not be used to send a cancellation request? Why does it have the be out of band?
Changing that to poll for a cancellation while working is a big change. Also, the server would need to buffer any pipelined requests while looking for a cancellation request. A second connection is not without wrinkles, but it avoids a lot of network complexity.
https://learn.microsoft.com/en-us/openspecs/windows_protocol...