Backport #89740 to 25.9: Avoid crash due to reading from remote server after disconnect in remote queries during cancellation

robot-clickhouse · robot-clickhouse · commit ae035ef05bea · 2025-11-24T15:15:37.000Z
diff --git a/src/Client/Connection.cpp b/src/Client/Connection.cpp
@@ -1008,7 +1008,7 @@ void Connection::sendCancel()
 {
     /// If we already disconnected.
     if (!out)
-        return;
+        throw Exception(ErrorCodes::NETWORK_ERROR, "Connection to {} terminated", getDescription());
 
     writeVarUInt(Protocol::Client::Cancel, *out);
     out->finishChunk();

Original file line number	Diff line number	Diff line change
`@@ -1008,7 +1008,7 @@ void Connection::sendCancel()`
`1008`	`1008`	`{`
`1009`	`1009`	`/// If we already disconnected.`
`1010`	`1010`	`if (!out)`
`1011`		`- return;`
	`1011`	`+ throw Exception(ErrorCodes::NETWORK_ERROR, "Connection to {} terminated", getDescription());`
`1012`	`1012`
`1013`	`1013`	`writeVarUInt(Protocol::Client::Cancel, *out);`
`1014`	`1014`	`out->finishChunk();`