postgres_fdw: Fix unexpected reporting of empty message.

pgfdw_report_error() in postgres_fdw gets a message from PGresult or
PGconn to report an error received from a remote server. Previously
if it could get a message from neither of them, it reported empty
message unexpectedly. The cause of this issue was that pgfdw_report_error()
didn't handle properly the case where no message could be obtained
and its local variable message_primary was set to '\0'.

This commit improves pgfdw_report_error() so that it reports the message
"could not obtain ..." when it gets no message and message_primary
is set to '\0'. This is the same behavior as when message_primary is NULL.

dblink_res_error() in dblink has the same issue, so this commit also
improves it in the same way.

Back-patch to all supported branches.

Author: Fujii Masao
Reviewed-by: Bharath Rupireddy
Discussion: https://postgr.es/m/477c16c8-7ea4-20fc-38d5-ed3a77ed616c@oss.nttdata.com

diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
index 105f8fb51725c02ff4b2f23d2d133e71e3fd3dc8..056e10a7d48d5485bd759174d567ce22172707d4 100644 (file)
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -2724,7 +2724,8 @@ dblink_res_error(PGconn *conn, const char *conname, PGresult *res,
 
    ereport(level,
            (errcode(sqlstate),
-            message_primary ? errmsg_internal("%s", message_primary) :
+            (message_primary != NULL && message_primary[0] != '\0') ?
+            errmsg_internal("%s", message_primary) :
             errmsg("could not obtain message string for remote error"),
             message_detail ? errdetail_internal("%s", message_detail) : 0,
             message_hint ? errhint("%s", message_hint) : 0,

diff --git a/contrib/postgres_fdw/connection.c b/contrib/postgres_fdw/connection.c
index 73c1be6d8f4fe11ca7ddd7186c305453da86c6f4..a023fb7fc9aea2386c72652591996906add32084 100644 (file)
--- a/contrib/postgres_fdw/connection.c
+++ b/contrib/postgres_fdw/connection.c
@@ -625,7 +625,8 @@ pgfdw_report_error(int elevel, PGresult *res, PGconn *conn,
 
        ereport(elevel,
                (errcode(sqlstate),
-                message_primary ? errmsg_internal("%s", message_primary) :
+                (message_primary != NULL && message_primary[0] != '\0') ?
+                errmsg_internal("%s", message_primary) :
                 errmsg("could not obtain message string for remote error"),
                 message_detail ? errdetail_internal("%s", message_detail) : 0,
                 message_hint ? errhint("%s", message_hint) : 0,