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The way CTRL-C in Postgres CLI cancels queries is incredibly hack-y

50 points

by andrenotgiant

2 days ago

| past

| 3 comments

| neon.com

| HN

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rlpb

1 minute ago

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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.

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michalc

53 minutes ago

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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?

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jtwaleson

1 hour ago

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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?

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toast0

1 hour ago

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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.

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bob1029

56 minutes ago

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MSSQL uses a special message over an existing connection:

https://learn.microsoft.com/en-us/openspecs/windows_protocol...