Fix incorrect error message for IDENTIFY_SYSTEM

danielgustafsson · danielgustafsson · commit b608afe980a5 · 2023-12-05T14:30:56.000+01:00
Commit 5a991ef accidentally reversed the order of the tuples and fields parameters, making the error message incorrectly refer to 3 tuples with 1 field when IDENTIFY_SYSTEM returns 1 tuple and 3 or 4 fields. Fix by changing the order of the parameters. This also adds a comment describing why we check for < 3 when postgres since 9.4 has been sending 4 fields. Backpatch all the way since the bug is almost a decade old. Author: Tomonari Katsumata <t.katsumata1122@gmail.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Bug: #18224 Backpatch-through: v12
diff --git a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
@@ -356,6 +356,10 @@ libpqrcv_identify_system(WalReceiverConn *conn, TimeLineID *primary_tli)
 						"the primary server: %s",
 						pchomp(PQerrorMessage(conn->streamConn)))));
 	}
+	/*
+	 * IDENTIFY_SERVER returns 3 columns in 9.3 and earlier, and 4 columns in
+	 * 9.4 and onwards.
+	 */
 	if (PQnfields(res) < 3 || PQntuples(res) != 1)
 	{
 		int			ntuples = PQntuples(res);
@@ -365,7 +369,7 @@ libpqrcv_identify_system(WalReceiverConn *conn, TimeLineID *primary_tli)
 		ereport(ERROR,
 				(errmsg("invalid response from primary server"),
 				 errdetail("Could not identify system: got %d rows and %d fields, expected %d rows and %d or more fields.",
-						   ntuples, nfields, 3, 1)));
+						   ntuples, nfields, 1, 3)));
 	}
 	primary_sysid = pstrdup(PQgetvalue(res, 0, 0));
 	*primary_tli = pg_strtoint32(PQgetvalue(res, 0, 1));

Original file line number	Diff line number	Diff line change
`@@ -356,6 +356,10 @@ libpqrcv_identify_system(WalReceiverConn conn, TimeLineID primary_tli)`
`356`	`356`	`"the primary server: %s",`
`357`	`357`	`pchomp(PQerrorMessage(conn->streamConn)))));`
`358`	`358`	`}`
	`359`	`+ /*`
	`360`	`+ * IDENTIFY_SERVER returns 3 columns in 9.3 and earlier, and 4 columns in`
	`361`	`+ * 9.4 and onwards.`
	`362`	`+ */`
`359`	`363`	`if (PQnfields(res) < 3 \|\| PQntuples(res) != 1)`
`360`	`364`	`{`
`361`	`365`	`int ntuples = PQntuples(res);`
`@@ -365,7 +369,7 @@ libpqrcv_identify_system(WalReceiverConn conn, TimeLineID primary_tli)`
`365`	`369`	`ereport(ERROR,`
`366`	`370`	`(errmsg("invalid response from primary server"),`
`367`	`371`	`errdetail("Could not identify system: got %d rows and %d fields, expected %d rows and %d or more fields.",`
`368`		`- ntuples, nfields, 3, 1)));`
	`372`	`+ ntuples, nfields, 1, 3)));`
`369`	`373`	`}`
`370`	`374`	`primary_sysid = pstrdup(PQgetvalue(res, 0, 0));`
`371`	`375`	`*primary_tli = pg_strtoint32(PQgetvalue(res, 0, 1));`