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 c8b0b4ff3fafda3cdb6193e209797a682c556435..d73c616f4f240cf5f33294e61053765375a5bea6 100644 (file)
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -2801,7 +2801,8 @@ 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 4aff315b7c3c2e12b81a8aef77d0f850e028b40e..5c0137220a9b6aab80a39e45f3d7414840ca60c2 100644 (file)
--- a/contrib/postgres_fdw/connection.c
+++ b/contrib/postgres_fdw/connection.c
@@ -824,7 +824,8 @@ 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,