Log the location field before any backtrace

This order makes more sense because the location is effectively at the
lowest level of the backtrace.

Discussion: https://www.postgresql.org/message-id/flat/90f5fa04-c410-a54e-9449-aa3749fb7972%402ndquadrant.com

src/backend/utils/error/elog.c

@@ -2938,13 +2938,6 @@ send_message_to_server_log(ErrorData *edata)
 			append_with_tabs(&buf, edata->context);
 			appendStringInfoChar(&buf, '\n');
 		}
-		if (edata->backtrace)
-		{
-			log_line_prefix(&buf, edata);
-			appendStringInfoString(&buf, _("BACKTRACE:  "));
-			append_with_tabs(&buf, edata->backtrace);
-			appendStringInfoChar(&buf, '\n');
-		}
 		if (Log_error_verbosity >= PGERROR_VERBOSE)
 		{
 			/* assume no newlines in funcname or filename... */
@@ -2962,6 +2955,13 @@ send_message_to_server_log(ErrorData *edata)
 								 edata->filename, edata->lineno);
 			}
 		}
+		if (edata->backtrace)
+		{
+			log_line_prefix(&buf, edata);
+			appendStringInfoString(&buf, _("BACKTRACE:  "));
+			append_with_tabs(&buf, edata->backtrace);
+			appendStringInfoChar(&buf, '\n');
+		}
 	}
 
 	/*