Improve dblink error message when remote does not provide it

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
index d4f9090f062a06b72dfc49ccd11473f2fda21d37..ee45cd244c60153c82d666e3d35f7d2af9f95e93 100644 (file)
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -2705,7 +2705,7 @@ 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
index bcdddc2db58238396a5eb92ae1f527583ec25dc2..5fabc99214b62977c730c24735df4af04b694b80 100644 (file)
--- a/contrib/postgres_fdw/connection.c
+++ b/contrib/postgres_fdw/connection.c
@@ -568,7 +568,7 @@ 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,