Open output file before sleeping in pg_recvlogical.

Let's complain about e.g an invalid path or permission problem sooner rather
than later. Before this patch, we would only try to open the output file
after receiving the first decoded message from the server.

src/bin/pg_basebackup/pg_recvlogical.c

@@ -315,6 +315,23 @@ StreamLog(void)
 		}
 		output_reopen = false;
 
+		/* open the output file, if not open yet */
+		if (outfd == -1)
+		{
+			if (strcmp(outfile, "-") == 0)
+				outfd = fileno(stdout);
+			else
+				outfd = open(outfile, O_CREAT | O_APPEND | O_WRONLY | PG_BINARY,
+							 S_IRUSR | S_IWUSR);
+			if (outfd == -1)
+			{
+				fprintf(stderr,
+						_("%s: could not open log file \"%s\": %s\n"),
+						progname, outfile, strerror(errno));
+				goto error;
+			}
+		}
+
 		r = PQgetCopyData(conn, &copybuf, 1);
 		if (r == 0)
 		{
@@ -479,23 +496,6 @@ StreamLog(void)
 			output_written_lsn = Max(temp, output_written_lsn);
 		}
 
-		/* open the output file, if not open yet */
-		if (outfd == -1)
-		{
-			if (strcmp(outfile, "-") == 0)
-				outfd = fileno(stdout);
-			else
-				outfd = open(outfile, O_CREAT | O_APPEND | O_WRONLY | PG_BINARY,
-							 S_IRUSR | S_IWUSR);
-			if (outfd == -1)
-			{
-				fprintf(stderr,
-						_("%s: could not open log file \"%s\": %s\n"),
-						progname, outfile, strerror(errno));
-				goto error;
-			}
-		}
-
 		bytes_left = r - hdr_len;
 		bytes_written = 0;