Improve dblink error message when remote does not provide it

jconway · jconway · commit 3272be346895 · 2016-12-21T15:51:46.000-08:00
When dblink or postgres_fdw detects an error on the remote side of the connection, it will try to construct a local error message as best it can using libpq's PQresultErrorField(). When no primary message is available, it was bailing out with an unhelpful "unknown error". Make that message better and more style guide compliant. Per discussion on hackers. Backpatch to 9.2 except postgres_fdw which didn't exist before 9.3. Discussion: https://postgr.es/m/19872.1482338965%40sss.pgh.pa.us
diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
@@ -2710,7 +2710,7 @@ dblink_res_error(const char *conname, PGresult *res, const char *dblink_context_
 	ereport(level,
 			(errcode(sqlstate),
 			 message_primary ? errmsg_internal("%s", message_primary) :
-			 errmsg("unknown error"),
+			 errmsg("could not obtain message string for remote error"),
 			 message_detail ? errdetail_internal("%s", message_detail) : 0,
 			 message_hint ? errhint("%s", message_hint) : 0,
 			 message_context ? errcontext("%s", message_context) : 0,
diff --git a/contrib/postgres_fdw/connection.c b/contrib/postgres_fdw/connection.c
@@ -496,7 +496,7 @@ pgfdw_report_error(int elevel, PGresult *res, PGconn *conn,
 		ereport(elevel,
 				(errcode(sqlstate),
 				 message_primary ? errmsg_internal("%s", message_primary) :
-				 errmsg("unknown error"),
+				 errmsg("could not obtain message string for remote error"),
 			   message_detail ? errdetail_internal("%s", message_detail) : 0,
 				 message_hint ? errhint("%s", message_hint) : 0,
 				 message_context ? errcontext("%s", message_context) : 0,
