Avoid redundantly prefixing PQerrorMessage for a connection failure.

libpq's error messages for connection failures pretty well stand on
their own, especially since commits 52a10224e/27a48e5a1.  Prefixing
them with 'could not connect to database "foo"' or the like is just
redundant, and perhaps even misleading if the specific database name
isn't relevant to the failure.  (When it is, we trust that the
backend's error message will include the DB name.)  Indeed, psql
hasn't used any such prefix in a long time.  So, make all our other
programs and documentation examples agree with psql's practice.

Discussion: https://postgr.es/m/1094524.1611266589@sss.pgh.pa.us

2 files changed, 6 insertions, 10 deletions

diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index b22cb38ca3b..b7a82453f0d 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -6837,8 +6837,8 @@ main(void)
 
     if (PQstatus(conn) != CONNECTION_OK)
     {
-        fprintf(stderr, "Connection to database failed: %s",
-                PQerrorMessage(conn));
+        /* PQerrorMessage's result includes a trailing newline */
+        fprintf(stderr, "%s", PQerrorMessage(conn));
         PQfinish(conn);
         return 1;
     }
@@ -8296,8 +8296,7 @@ main(int argc, char **argv)
     /* Check to see that the backend connection was successfully made */
     if (PQstatus(conn) != CONNECTION_OK)
     {
-        fprintf(stderr, "Connection to database failed: %s",
-                PQerrorMessage(conn));
+        fprintf(stderr, "%s", PQerrorMessage(conn));
         exit_nicely(conn);
     }
 
@@ -8466,8 +8465,7 @@ main(int argc, char **argv)
     /* Check to see that the backend connection was successfully made */
     if (PQstatus(conn) != CONNECTION_OK)
     {
-        fprintf(stderr, "Connection to database failed: %s",
-                PQerrorMessage(conn));
+        fprintf(stderr, "%s", PQerrorMessage(conn));
         exit_nicely(conn);
     }
 
@@ -8694,8 +8692,7 @@ main(int argc, char **argv)
     /* Check to see that the backend connection was successfully made */
     if (PQstatus(conn) != CONNECTION_OK)
     {
-        fprintf(stderr, "Connection to database failed: %s",
-                PQerrorMessage(conn));
+        fprintf(stderr, "%s", PQerrorMessage(conn));
         exit_nicely(conn);
     }
 
diff --git a/doc/src/sgml/lobj.sgml b/doc/src/sgml/lobj.sgml
index 413eda50af3..6d46da42e27 100644
--- a/doc/src/sgml/lobj.sgml
+++ b/doc/src/sgml/lobj.sgml
@@ -939,8 +939,7 @@ main(int argc, char **argv)
     /* check to see that the backend connection was successfully made */
     if (PQstatus(conn) != CONNECTION_OK)
     {
-        fprintf(stderr, "Connection to database failed: %s",
-                PQerrorMessage(conn));
+        fprintf(stderr, "%s", PQerrorMessage(conn));
         exit_nicely(conn);
     }