Add support for piping COPY to/from an external program.

This includes backend "COPY TO/FROM PROGRAM '...'" syntax, and corresponding
psql \copy syntax. Like with reading/writing files, the backend version is
superuser-only, and in the psql version, the program is run in the client.

In the passing, the psql \copy STDIN/STDOUT syntax is subtly changed: if you
the stdin/stdout is quoted, it's now interpreted as a filename. For example,
"\copy foo from 'stdin'" now reads from a file called 'stdin', not from
standard input. Before this, there was no way to specify a filename called
stdin, stdout, pstdin or pstdout.

This creates a new function in pgport, wait_result_to_str(), which can
be used to convert the exit status of a process, as returned by wait(3),
to a human-readable string.

Etsuro Fujita, reviewed by Amit Kapila.

1 files changed, 10 insertions, 27 deletions

diff --git a/src/port/exec.c b/src/port/exec.c
index 18be1408f7a..01203c056cc 100644
--- a/src/port/exec.c
+++ b/src/port/exec.c
@@ -505,14 +505,12 @@ pipe_read_line(char *cmd, char *line, int maxsize)
 
 /*
  * pclose() plus useful error reporting
- * Is this necessary?  bjm 2004-05-11
- * Originally this was stated to be here because pipe.c had backend linkage.
- * Perhaps that's no longer so now we have got rid of pipe.c amd 2012-03-28
  */
 int
 pclose_check(FILE *stream)
 {
 	int			exitstatus;
+	char	   *reason;
 
 	exitstatus = pclose(stream);
 
@@ -522,36 +520,21 @@ pclose_check(FILE *stream)
 	if (exitstatus == -1)
 	{
 		/* pclose() itself failed, and hopefully set errno */
-		perror("pclose failed");
+		log_error(_("pclose failed: %s"), strerror(errno));
 	}
-	else if (WIFEXITED(exitstatus))
-		log_error(_("child process exited with exit code %d"),
-				  WEXITSTATUS(exitstatus));
-	else if (WIFSIGNALED(exitstatus))
-#if defined(WIN32)
-		log_error(_("child process was terminated by exception 0x%X"),
-				  WTERMSIG(exitstatus));
-#elif defined(HAVE_DECL_SYS_SIGLIST) && HAVE_DECL_SYS_SIGLIST
+	else
 	{
-		char		str[256];
-
-		snprintf(str, sizeof(str), "%d: %s", WTERMSIG(exitstatus),
-				 WTERMSIG(exitstatus) < NSIG ?
-				 sys_siglist[WTERMSIG(exitstatus)] : "(unknown)");
-		log_error(_("child process was terminated by signal %s"), str);
-	}
+		reason = wait_result_to_str(exitstatus);
+		log_error("%s", reason);
+#ifdef FRONTEND
+		free(reason);
 #else
-		log_error(_("child process was terminated by signal %d"),
-				  WTERMSIG(exitstatus));
+		pfree(reason);
 #endif
-	else
-		log_error(_("child process exited with unrecognized status %d"),
-				  exitstatus);
-
-	return -1;
+	}
+	return exitstatus;
 }
 
-
 /*
  *	set_pglocale_pgservice
  *