text: /*
   * psql - the PostgreSQL interactive terminal
   *
   * Copyright (c) 2000-2014, PostgreSQL Global Development Group
   *
   * src/bin/psql/common.c
   */
  #include "postgres_fe.h"
  #include "common.h"
  
  #include <ctype.h>
  #include <signal.h>
  #ifndef WIN32
  #include <unistd.h>				/* for write() */
  #else
  #include <io.h>					/* for _write() */
  #include <win32.h>
  #endif
  
  #include "portability/instr_time.h"
  
  #include "settings.h"
  #include "command.h"
  #include "copy.h"
  #include "mbprint.h"
  
  
  
  static bool ExecQueryUsingCursor(const char *query, double *elapsed_msec);
  static bool command_no_begin(const char *query);
  static bool is_select_command(const char *query);
  
  /*
   * setQFout
   * -- handler for -o command line option and \o command
   *
   * Tries to open file fname (or pipe if fname starts with '|')
   * and stores the file handle in pset)
   * Upon failure, sets stdout and returns false.
   */
  bool
  setQFout(const char *fname)
  {
  	bool		status = true;
  
  	/* Close old file/pipe */
  	if (pset.queryFout && pset.queryFout != stdout && pset.queryFout != stderr)
  	{
  		if (pset.queryFoutPipe)
  			pclose(pset.queryFout);
  		else
  			fclose(pset.queryFout);
  	}
  
  	/* If no filename, set stdout */
  	if (!fname || fname[0] == '\0')
  	{
  		pset.queryFout = stdout;
  		pset.queryFoutPipe = false;
  	}
  	else if (*fname == '|')
  	{
  		pset.queryFout = popen(fname + 1, "w");
  		pset.queryFoutPipe = true;
  	}
  	else
  	{
  		pset.queryFout = fopen(fname, "w");
  		pset.queryFoutPipe = false;
  	}
  
  	if (!(pset.queryFout))
  	{
  		psql_error("%s: %s\n", fname, strerror(errno));
  		pset.queryFout = stdout;
  		pset.queryFoutPipe = false;
  		status = false;
  	}
  
  	/* Direct signals */
  #ifndef WIN32
  	pqsignal(SIGPIPE, pset.queryFoutPipe ? SIG_IGN : SIG_DFL);
  #endif
  
  	return status;
  }
  
  
  
  /*
   * Error reporting for scripts. Errors should look like
   *	 psql:filename:lineno: message
   *
   */
  void
  psql_error(const char *fmt,...)
  {
  	va_list		ap;
  
  	fflush(stdout);
  	if (pset.queryFout && pset.queryFout != stdout)
  		fflush(pset.queryFout);
  
  	if (pset.inputfile)
  		fprintf(stderr, "%s:%s:" UINT64_FORMAT ": ", pset.progname, pset.inputfile, pset.lineno);
  	va_start(ap, fmt);
  	vfprintf(stderr, _(fmt), ap);
  	va_end(ap);
  }
  
  
  
  /*
   * for backend Notice messages (INFO, WARNING, etc)
   */
  void
  NoticeProcessor(void *arg, const char *message)
  {
  	(void) arg;					/* not used */
  	psql_error("%s", message);
  }
  
  
  
  /*
   * Code to support query cancellation
   *
   * Before we start a query, we enable the SIGINT signal catcher to send a
   * cancel request to the backend. Note that sending the cancel directly from
   * the signal handler is safe because PQcancel() is written to make it
   * so. We use write() to report to stderr because it's better to use simple
   * facilities in a signal handler.
   *
   * On win32, the signal canceling happens on a separate thread, because
   * that's how SetConsoleCtrlHandler works. The PQcancel function is safe
   * for this (unlike PQrequestCancel). However, a CRITICAL_SECTION is required
   * to protect the PGcancel structure against being changed while the signal
   * thread is using it.
   *
   * SIGINT is supposed to abort all long-running psql operations, not only
   * database queries.  In most places, this is accomplished by checking
   * cancel_pressed during long-running loops.  However, that won't work when
   * blocked on user input (in readline() or fgets()).  In those places, we
   * set sigint_interrupt_enabled TRUE while blocked, instructing the signal
   * catcher to longjmp through sigint_interrupt_jmp.  We assume readline and
   * fgets are coded to handle possible interruption.  (XXX currently this does
   * not work on win32, so control-C is less useful there)
   */
  volatile bool sigint_interrupt_enabled = false;
  
  sigjmp_buf	sigint_interrupt_jmp;
  
  static PGcancel *volatile cancelConn = NULL;
  
  #ifdef WIN32
  static CRITICAL_SECTION cancelConnLock;
  #endif
  
  /* Used from signal handlers, no buffering */
  #define write_stderr(str)	write(fileno(stderr), str, strlen(str))
  
  
  #ifndef WIN32
  
  static void
  handle_sigint(SIGNAL_ARGS)
  {
  	int			save_errno = errno;
  	int			rc;
  	char		errbuf[256];
  
  	/* if we are waiting for input, longjmp out of it */
  	if (sigint_interrupt_enabled)
  	{
  		sigint_interrupt_enabled = false;
  		siglongjmp(sigint_interrupt_jmp, 1);
  	}
  
  	/* else, set cancel flag to stop any long-running loops */
  	cancel_pressed = true;
  
  	/* and send QueryCancel if we are processing a database query */
  	if (cancelConn != NULL)
  	{
  		if (PQcancel(cancelConn, errbuf, sizeof(errbuf)))
  		{
  			rc = write_stderr("Cancel request sent\n");
  			(void) rc;			/* ignore errors, nothing we can do here */
  		}
  		else
  		{
  			rc = write_stderr("Could not send cancel request: ");
  			(void) rc;			/* ignore errors, nothing we can do here */
  			rc = write_stderr(errbuf);
  			(void) rc;			/* ignore errors, nothing we can do here */
  		}
  	}
  
  	errno = save_errno;			/* just in case the write changed it */
  }
  
  void
  setup_cancel_handler(void)
  {
  	pqsignal(SIGINT, handle_sigint);
  }
  #else							/* WIN32 */
  
  static BOOL WINAPI
  consoleHandler(DWORD dwCtrlType)
  {
  	char		errbuf[256];
  
  	if (dwCtrlType == CTRL_C_EVENT ||
  		dwCtrlType == CTRL_BREAK_EVENT)
  	{
  		/*
  		 * Can't longjmp here, because we are in wrong thread :-(
  		 */
  
  		/* set cancel flag to stop any long-running loops */
  		cancel_pressed = true;
  
  		/* and send QueryCancel if we are processing a database query */
  		EnterCriticalSection(&cancelConnLock);
  		if (cancelConn != NULL)
  		{
  			if (PQcancel(cancelConn, errbuf, sizeof(errbuf)))
  				write_stderr("Cancel request sent\n");
  			else
  			{
  				write_stderr("Could not send cancel request: ");
  				write_stderr(errbuf);
  			}
  		}
  		LeaveCriticalSection(&cancelConnLock);
  
  		return TRUE;
  	}
  	else
  		/* Return FALSE for any signals not being handled */
  		return FALSE;
  }
  
  void
  setup_cancel_handler(void)
  {
  	InitializeCriticalSection(&cancelConnLock);
  
  	SetConsoleCtrlHandler(consoleHandler, TRUE);
  }
  #endif   /* WIN32 */
  
  
  /* ConnectionUp
   *
   * Returns whether our backend connection is still there.
   */
  static bool
  ConnectionUp(void)
  {
  	return PQstatus(pset.db) != CONNECTION_BAD;
  }
  
  
  
  /* CheckConnection
   *
   * Verify that we still have a good connection to the backend, and if not,
   * see if it can be restored.
   *
   * Returns true if either the connection was still there, or it could be
   * restored successfully; false otherwise.  If, however, there was no
   * connection and the session is non-interactive, this will exit the program
   * with a code of EXIT_BADCONN.
   */
  static bool
  CheckConnection(void)
  {
  	bool		OK;
  
  	OK = ConnectionUp();
  	if (!OK)
  	{
  		if (!pset.cur_cmd_interactive)
  		{
  			psql_error("connection to server was lost\n");
  			exit(EXIT_BADCONN);
  		}
  
  		psql_error("The connection to the server was lost. Attempting reset: ");
  		PQreset(pset.db);
  		OK = ConnectionUp();
  		if (!OK)
  		{
  			psql_error("Failed.\n");
  			PQfinish(pset.db);
  			pset.db = NULL;
  			ResetCancelConn();
  			UnsyncVariables();
  		}
  		else
  			psql_error("Succeeded.\n");
  	}
  
  	return OK;
  }
  
  
  
  /*
   * SetCancelConn
   *
   * Set cancelConn to point to the current database connection.
   */
  void
  SetCancelConn(void)
  {
  	PGcancel   *oldCancelConn;
  
  #ifdef WIN32
  	EnterCriticalSection(&cancelConnLock);
  #endif
  
  	/* Free the old one if we have one */
  	oldCancelConn = cancelConn;
  	/* be sure handle_sigint doesn't use pointer while freeing */
  	cancelConn = NULL;
  
  	if (oldCancelConn != NULL)
  		PQfreeCancel(oldCancelConn);
  
  	cancelConn = PQgetCancel(pset.db);
  
  #ifdef WIN32
  	LeaveCriticalSection(&cancelConnLock);
  #endif
  }
  
  
  /*
   * ResetCancelConn
   *
   * Free the current cancel connection, if any, and set to NULL.
   */
  void
  ResetCancelConn(void)
  {
  	PGcancel   *oldCancelConn;
  
  #ifdef WIN32
  	EnterCriticalSection(&cancelConnLock);
  #endif
  
  	oldCancelConn = cancelConn;
  	/* be sure handle_sigint doesn't use pointer while freeing */
  	cancelConn = NULL;
  
  	if (oldCancelConn != NULL)
  		PQfreeCancel(oldCancelConn);
  
  #ifdef WIN32
  	LeaveCriticalSection(&cancelConnLock);
  #endif
  }
  
  
  /*
   * AcceptResult
   *
   * Checks whether a result is valid, giving an error message if necessary;
   * and ensures that the connection to the backend is still up.
   *
   * Returns true for valid result, false for error state.
   */
  static bool
  AcceptResult(const PGresult *result)
  {
  	bool		OK;
  
  	if (!result)
  		OK = false;
  	else
  		switch (PQresultStatus(result))
  		{
  			case PGRES_COMMAND_OK:
  			case PGRES_TUPLES_OK:
  			case PGRES_EMPTY_QUERY:
  			case PGRES_COPY_IN:
  			case PGRES_COPY_OUT:
  				/* Fine, do nothing */
  				OK = true;
  				break;
  
  			case PGRES_BAD_RESPONSE:
  			case PGRES_NONFATAL_ERROR:
  			case PGRES_FATAL_ERROR:
  				OK = false;
  				break;
  
  			default:
  				OK = false;
  				psql_error("unexpected PQresultStatus: %d\n",
  						   PQresultStatus(result));
  				break;
  		}
  
  	if (!OK)
  	{
  		const char *error = PQerrorMessage(pset.db);
  
  		if (strlen(error))
  			psql_error("%s", error);
  
  		CheckConnection();
  	}
  
  	return OK;
  }
  
  
  
  /*
   * PSQLexec
   *
   * This is the way to send "backdoor" queries (those not directly entered
   * by the user). It is subject to -E but not -e.
   *
   * Caller is responsible for handling the ensuing processing if a COPY
   * command is sent.
   *
   * Note: we don't bother to check PQclientEncoding; it is assumed that no
   * caller uses this path to issue "SET CLIENT_ENCODING".
   */
  PGresult *
  PSQLexec(const char *query)
  {
  	PGresult   *res;
  
  	if (!pset.db)
  	{
  		psql_error("You are currently not connected to a database.\n");
  		return NULL;
  	}
  
  	if (pset.echo_hidden != PSQL_ECHO_HIDDEN_OFF)
  	{
  		printf(_("********* QUERY **********\n"
  				 "%s\n"
  				 "**************************\n\n"), query);
  		fflush(stdout);
  		if (pset.logfile)
  		{
  			fprintf(pset.logfile,
  					_("********* QUERY **********\n"
  					  "%s\n"
  					  "**************************\n\n"), query);
  			fflush(pset.logfile);
  		}
  
  		if (pset.echo_hidden == PSQL_ECHO_HIDDEN_NOEXEC)
  			return NULL;
  	}
  
  	SetCancelConn();
  
  	res = PQexec(pset.db, query);
  
  	ResetCancelConn();
  
  	if (!AcceptResult(res))
  	{
  		PQclear(res);
  		res = NULL;
  	}
  
  	return res;
  }
  
  
  /*
   * PSQLexecWatch
   *
   * This function is used for \watch command to send the query to
   * the server and print out the results.
   *
   * Returns 1 if the query executed successfully, 0 if it cannot be repeated,
   * e.g., because of the interrupt, -1 on error.
   */
  int
  PSQLexecWatch(const char *query, const printQueryOpt *opt)
  {
  	PGresult   *res;
  	double	elapsed_msec = 0;
  	instr_time	before;
  	instr_time	after;
  
  	if (!pset.db)
  	{
  		psql_error("You are currently not connected to a database.\n");
  		return 0;
  	}
  
  	SetCancelConn();
  
  	if (pset.timing)
  		INSTR_TIME_SET_CURRENT(before);
  
  	res = PQexec(pset.db, query);
  
  	ResetCancelConn();
  
  	if (!AcceptResult(res))
  	{
  		PQclear(res);
  		return 0;
  	}
  
  	if (pset.timing)
  	{
  		INSTR_TIME_SET_CURRENT(after);
  		INSTR_TIME_SUBTRACT(after, before);
  		elapsed_msec = INSTR_TIME_GET_MILLISEC(after);
  	}
  
  	/*
  	 * If SIGINT is sent while the query is processing, the interrupt
  	 * will be consumed.  The user's intention, though, is to cancel
  	 * the entire watch process, so detect a sent cancellation request and
  	 * exit in this case.
  	 */
  	if (cancel_pressed)
  	{
  		PQclear(res);
  		return 0;
  	}
  
  	switch (PQresultStatus(res))
  	{
  		case PGRES_TUPLES_OK:
  			printQuery(res, opt, pset.queryFout, pset.logfile);
  			break;
  
  		case PGRES_COMMAND_OK:
  			fprintf(pset.queryFout, "%s\n%s\n\n", opt->title, PQcmdStatus(res));
  			break;
  
  		case PGRES_EMPTY_QUERY:
  			psql_error(_("\\watch cannot be used with an empty query\n"));
  			PQclear(res);
  			return -1;
  
  		case PGRES_COPY_OUT:
  		case PGRES_COPY_IN:
  		case PGRES_COPY_BOTH:
  			psql_error(_("\\watch cannot be used with COPY\n"));
  			PQclear(res);
  			return -1;
  
  		default:
  			psql_error(_("unexpected result status for \\watch\n"));
  			PQclear(res);
  			return -1;
  	}
  
  	PQclear(res);
  
  	fflush(pset.queryFout);
  
  	/* Possible microtiming output */
  	if (pset.timing)
  		printf(_("Time: %.3f ms\n"), elapsed_msec);
  
  	return 1;
  }
  
  
  /*
   * PrintNotifications: check for asynchronous notifications, and print them out
   */
  static void
  PrintNotifications(void)
  {
  	PGnotify   *notify;
  
  	while ((notify = PQnotifies(pset.db)))
  	{
  		/* for backward compatibility, only show payload if nonempty */
  		if (notify->extra[0])
  			fprintf(pset.queryFout, _("Asynchronous notification \"%s\" with payload \"%s\" received from server process with PID %d.\n"),
  					notify->relname, notify->extra, notify->be_pid);
  		else
  			fprintf(pset.queryFout, _("Asynchronous notification \"%s\" received from server process with PID %d.\n"),
  					notify->relname, notify->be_pid);
  		fflush(pset.queryFout);
  		PQfreemem(notify);
  	}
  }
  
  
  /*
   * PrintQueryTuples: assuming query result is OK, print its tuples
   *
   * Returns true if successful, false otherwise.
   */
  static bool
  PrintQueryTuples(const PGresult *results)
  {
  	printQueryOpt my_popt = pset.popt;
  
  	/* write output to \g argument, if any */
  	if (pset.gfname)
  	{
  		/* keep this code in sync with ExecQueryUsingCursor */
  		FILE	   *queryFout_copy = pset.queryFout;
  		bool		queryFoutPipe_copy = pset.queryFoutPipe;
  
  		pset.queryFout = stdout;	/* so it doesn't get closed */
  
  		/* open file/pipe */
  		if (!setQFout(pset.gfname))
  		{
  			pset.queryFout = queryFout_copy;
  			pset.queryFoutPipe = queryFoutPipe_copy;
  			return false;
  		}
  
  		printQuery(results, &my_popt, pset.queryFout, pset.logfile);
  
  		/* close file/pipe, restore old setting */
  		setQFout(NULL);
  
  		pset.queryFout = queryFout_copy;
  		pset.queryFoutPipe = queryFoutPipe_copy;
  	}
  	else
  		printQuery(results, &my_popt, pset.queryFout, pset.logfile);
  
  	return true;
  }
  
  
  /*
   * StoreQueryTuple: assuming query result is OK, save data into variables
   *
   * Returns true if successful, false otherwise.
   */
  static bool
  StoreQueryTuple(const PGresult *result)
  {
  	bool		success = true;
  
  	if (PQntuples(result) < 1)
  	{
  		psql_error("no rows returned for \\gset\n");
  		success = false;
  	}
  	else if (PQntuples(result) > 1)
  	{
  		psql_error("more than one row returned for \\gset\n");
  		success = false;
  	}
  	else
  	{
  		int			i;
  
  		for (i = 0; i < PQnfields(result); i++)
  		{
  			char	   *colname = PQfname(result, i);
  			char	   *varname;
  			char	   *value;
  
  			/* concate prefix and column name */
  			varname = psprintf("%s%s", pset.gset_prefix, colname);
  
  			if (!PQgetisnull(result, 0, i))
  				value = PQgetvalue(result, 0, i);
  			else
  			{
  				/* for NULL value, unset rather than set the variable */
  				value = NULL;
  			}
  
  			if (!SetVariable(pset.vars, varname, value))
  			{
  				psql_error("could not set variable \"%s\"\n", varname);
  				free(varname);
  				success = false;
  				break;
  			}
  
  			free(varname);
  		}
  	}
  
  	return success;
  }
  
  
  /*
   * ProcessResult: utility function for use by SendQuery() only
   *
   * When our command string contained a COPY FROM STDIN or COPY TO STDOUT,
   * PQexec() has stopped at the PGresult associated with the first such
   * command.  In that event, we'll marshal data for the COPY and then cycle
   * through any subsequent PGresult objects.
   *
   * When the command string contained no such COPY command, this function
   * degenerates to an AcceptResult() call.
   *
   * Changes its argument to point to the last PGresult of the command string,
   * or NULL if that result was for a COPY TO STDOUT.  (Returning NULL prevents
   * the command status from being printed, which we want in that case so that
   * the status line doesn't get taken as part of the COPY data.)
   *
   * Returns true on complete success, false otherwise.  Possible failure modes
   * include purely client-side problems; check the transaction status for the
   * server-side opinion.
   */
  static bool
  ProcessResult(PGresult **results)
  {
  	bool		success = true;
  	bool		first_cycle = true;
  
  	for (;;)
  	{
  		ExecStatusType result_status;
  		bool		is_copy;
  		PGresult   *next_result;
  
  		if (!AcceptResult(*results))
  		{
  			/*
  			 * Failure at this point is always a server-side failure or a
  			 * failure to submit the command string.  Either way, we're
  			 * finished with this command string.
  			 */
  			success = false;
  			break;
  		}
  
  		result_status = PQresultStatus(*results);
  		switch (result_status)
  		{
  			case PGRES_EMPTY_QUERY:
  			case PGRES_COMMAND_OK:
  			case PGRES_TUPLES_OK:
  				is_copy = false;
  				break;
  
  			case PGRES_COPY_OUT:
  			case PGRES_COPY_IN:
  				is_copy = true;
  				break;
  
  			default:
  				/* AcceptResult() should have caught anything else. */
  				is_copy = false;
  				psql_error("unexpected PQresultStatus: %d\n", result_status);
  				break;
  		}
  
  		if (is_copy)
  		{
  			/*
  			 * Marshal the COPY data.  Either subroutine will get the
  			 * connection out of its COPY state, then call PQresultStatus()
  			 * once and report any error.
  			 *
  			 * If pset.copyStream is set, use that as data source/sink,
  			 * otherwise use queryFout or cur_cmd_source as appropriate.
  			 */
  			FILE	   *copystream = pset.copyStream;
  			PGresult   *copy_result;
  
  			SetCancelConn();
  			if (result_status == PGRES_COPY_OUT)
  			{
  				if (!copystream)
  					copystream = pset.queryFout;
  				success = handleCopyOut(pset.db,
  										copystream,
  										&copy_result) && success;
  
  				/*
  				 * Suppress status printing if the report would go to the same
  				 * place as the COPY data just went.  Note this doesn't
  				 * prevent error reporting, since handleCopyOut did that.
  				 */
  				if (copystream == pset.queryFout)
  				{
  					PQclear(copy_result);
  					copy_result = NULL;
  				}
  			}
  			else
  			{
  				if (!copystream)
  					copystream = pset.cur_cmd_source;
  				success = handleCopyIn(pset.db,
  									   copystream,
  									   PQbinaryTuples(*results),
  									   &copy_result) && success;
  			}
  			ResetCancelConn();
  
  			/*
  			 * Replace the PGRES_COPY_OUT/IN result with COPY command's exit
  			 * status, or with NULL if we want to suppress printing anything.
  			 */
  			PQclear(*results);
  			*results = copy_result;
  		}
  		else if (first_cycle)
  		{
  			/* fast path: no COPY commands; PQexec visited all results */
  			break;
  		}
  
  		/*
  		 * Check PQgetResult() again.  In the typical case of a single-command
  		 * string, it will return NULL.  Otherwise, we'll have other results
  		 * to process that may include other COPYs.  We keep the last result.
  		 */
  		next_result = PQgetResult(pset.db);
  		if (!next_result)
  			break;
  
  		PQclear(*results);
  		*results = next_result;
  		first_cycle = false;
  	}
  
  	/* may need this to recover from conn loss during COPY */
  	if (!first_cycle && !CheckConnection())
  		return false;
  
  	return success;
  }
  
  
  /*
   * PrintQueryStatus: report command status as required
   *
   * Note: Utility function for use by PrintQueryResults() only.
   */
  static void
  PrintQueryStatus(PGresult *results)
  {
  	char		buf[16];
  
  	if (!pset.quiet)
  	{
  		if (pset.popt.topt.format == PRINT_HTML)
  		{
  			fputs("<p>", pset.queryFout);
  			html_escaped_print(PQcmdStatus(results), pset.queryFout);
  			fputs("</p>\n", pset.queryFout);
  		}
  		else
  			fprintf(pset.queryFout, "%s\n", PQcmdStatus(results));
  	}
  
  	if (pset.logfile)
  		fprintf(pset.logfile, "%s\n", PQcmdStatus(results));
  
  	snprintf(buf, sizeof(buf), "%u", (unsigned int) PQoidValue(results));
  	SetVariable(pset.vars, "LASTOID", buf);
  }
  
  
  /*
   * PrintQueryResults: print out (or store) query results as required
   *
   * Note: Utility function for use by SendQuery() only.
   *
   * Returns true if the query executed successfully, false otherwise.
   */
  static bool
  PrintQueryResults(PGresult *results)
  {
  	bool		success;
  	const char *cmdstatus;
  
  	if (!results)
  		return false;
  
  	switch (PQresultStatus(results))
  	{
  		case PGRES_TUPLES_OK:
  			/* store or print the data ... */
  			if (pset.gset_prefix)
  				success = StoreQueryTuple(results);
  			else
  				success = PrintQueryTuples(results);
  			/* if it's INSERT/UPDATE/DELETE RETURNING, also print status */
  			cmdstatus = PQcmdStatus(results);
  			if (strncmp(cmdstatus, "INSERT", 6) == 0 ||
  				strncmp(cmdstatus, "UPDATE", 6) == 0 ||
  				strncmp(cmdstatus, "DELETE", 6) == 0)
  				PrintQueryStatus(results);
  			break;
  
  		case PGRES_COMMAND_OK:
  			PrintQueryStatus(results);
  			success = true;
  			break;
  
  		case PGRES_EMPTY_QUERY:
  			success = true;
  			break;
  
  		case PGRES_COPY_OUT:
  		case PGRES_COPY_IN:
  			/* nothing to do here */
  			success = true;
  			break;
  
  		case PGRES_BAD_RESPONSE:
  		case PGRES_NONFATAL_ERROR:
  		case PGRES_FATAL_ERROR:
  			success = false;
  			break;
  
  		default:
  			success = false;
  			psql_error("unexpected PQresultStatus: %d\n",
  					   PQresultStatus(results));
  			break;
  	}
  
  	fflush(pset.queryFout);
  
  	return success;
  }
  
  
  /*
   * SendQuery: send the query string to the backend
   * (and print out results)
   *
   * Note: This is the "front door" way to send a query. That is, use it to
   * send queries actually entered by the user. These queries will be subject to
   * single step mode.
   * To send "back door" queries (generated by slash commands, etc.) in a
   * controlled way, use PSQLexec().
   *
   * Returns true if the query executed successfully, false otherwise.
   */
  bool
  SendQuery(const char *query)
  {
  	PGresult   *results;
  	PGTransactionStatusType transaction_status;
  	double		elapsed_msec = 0;
  	bool		OK = false;
  	bool		on_error_rollback_savepoint = false;
  	static bool on_error_rollback_warning = false;
  
  	if (!pset.db)
  	{
  		psql_error("You are currently not connected to a database.\n");
  		goto sendquery_cleanup;
  	}
  
  	if (pset.singlestep)
  	{
  		char		buf[3];
  
  		printf(_("***(Single step mode: verify command)*******************************************\n"
  				 "%s\n"
  				 "***(press return to proceed or enter x and return to cancel)********************\n"),
  			   query);
  		fflush(stdout);
  		if (fgets(buf, sizeof(buf), stdin) != NULL)
  			if (buf[0] == 'x')
  				goto sendquery_cleanup;
  	}
  	else if (pset.echo == PSQL_ECHO_QUERIES)
  	{
  		puts(query);
  		fflush(stdout);
  	}
  
  	if (pset.logfile)
  	{
  		fprintf(pset.logfile,
  				_("********* QUERY **********\n"
  				  "%s\n"
  				  "**************************\n\n"), query);
  		fflush(pset.logfile);
  	}
  
  	SetCancelConn();
  
  	transaction_status = PQtransactionStatus(pset.db);
  
  	if (transaction_status == PQTRANS_IDLE &&
  		!pset.autocommit &&
  		!command_no_begin(query))
  	{
  		results = PQexec(pset.db, "BEGIN");
  		if (PQresultStatus(results) != PGRES_COMMAND_OK)
  		{
  			psql_error("%s", PQerrorMessage(pset.db));
  			PQclear(results);
  			ResetCancelConn();
  			goto sendquery_cleanup;
  		}
  		PQclear(results);
  		transaction_status = PQtransactionStatus(pset.db);
  	}
  
  	if (transaction_status == PQTRANS_INTRANS &&
  		pset.on_error_rollback != PSQL_ERROR_ROLLBACK_OFF &&
  		(pset.cur_cmd_interactive ||
  		 pset.on_error_rollback == PSQL_ERROR_ROLLBACK_ON))
  	{
  		if (on_error_rollback_warning == false && pset.sversion < 80000)
  		{
  			psql_error("The server (version %d.%d) does not support savepoints for ON_ERROR_ROLLBACK.\n",
  					   pset.sversion / 10000, (pset.sversion / 100) % 100);
  			on_error_rollback_warning = true;
  		}
  		else
  		{
  			results = PQexec(pset.db, "SAVEPOINT pg_psql_temporary_savepoint");
  			if (PQresultStatus(results) != PGRES_COMMAND_OK)
  			{
  				psql_error("%s", PQerrorMessage(pset.db));
  				PQclear(results);
  				ResetCancelConn();
  				goto sendquery_cleanup;
  			}
  			PQclear(results);
  			on_error_rollback_savepoint = true;
  		}
  	}
  
  	if (pset.fetch_count <= 0 || !is_select_command(query))
  	{
  		/* Default fetch-it-all-and-print mode */
  		instr_time	before,
  					after;
  
  		if (pset.timing)
  			INSTR_TIME_SET_CURRENT(before);
  
  		results = PQexec(pset.db, query);
  
  		/* these operations are included in the timing result: */
  		ResetCancelConn();
  		OK = ProcessResult(&results);
  
  		if (pset.timing)
  		{
  			INSTR_TIME_SET_CURRENT(after);
  			INSTR_TIME_SUBTRACT(after, before);
  			elapsed_msec = INSTR_TIME_GET_MILLISEC(after);
  		}
  
  		/* but printing results isn't: */
  		if (OK && results)
  			OK = PrintQueryResults(results);
  	}
  	else
  	{
  		/* Fetch-in-segments mode */
  		OK = ExecQueryUsingCursor(query, &elapsed_msec);
  		ResetCancelConn();
  		results = NULL;			/* PQclear(NULL) does nothing */
  	}
  
  	if (!OK && pset.echo == PSQL_ECHO_ERRORS)
  		psql_error("STATEMENT:  %s\n", query);
  
  	/* If we made a temporary savepoint, possibly release/rollback */
  	if (on_error_rollback_savepoint)
  	{
  		const char *svptcmd = NULL;
  
  		transaction_status = PQtransactionStatus(pset.db);
  
  		switch (transaction_status)
  		{
  			case PQTRANS_INERROR:
  				/* We always rollback on an error */
  				svptcmd = "ROLLBACK TO pg_psql_temporary_savepoint";
  				break;
  
  			case PQTRANS_IDLE:
  				/* If they are no longer in a transaction, then do nothing */
  				break;
  
  			case PQTRANS_INTRANS:
  
  				/*
  				 * Do nothing if they are messing with savepoints themselves:
  				 * If the user did RELEASE or ROLLBACK, our savepoint is gone.
  				 * If they issued a SAVEPOINT, releasing ours would remove
  				 * theirs.
  				 */
  				if (results &&
  					(strcmp(PQcmdStatus(results), "SAVEPOINT") == 0 ||
  					 strcmp(PQcmdStatus(results), "RELEASE") == 0 ||
  					 strcmp(PQcmdStatus(results), "ROLLBACK") == 0))
  					svptcmd = NULL;
  				else
  					svptcmd = "RELEASE pg_psql_temporary_savepoint";
  				break;
  
  			case PQTRANS_ACTIVE:
  			case PQTRANS_UNKNOWN:
  			default:
  				OK = false;
  				/* PQTRANS_UNKNOWN is expected given a broken connection. */
  				if (transaction_status != PQTRANS_UNKNOWN || ConnectionUp())
  					psql_error("unexpected transaction status (%d)\n",
  							   transaction_status);
  				break;
  		}
  
  		if (svptcmd)
  		{
  			PGresult   *svptres;
  
  			svptres = PQexec(pset.db, svptcmd);
  			if (PQresultStatus(svptres) != PGRES_COMMAND_OK)
  			{
  				psql_error("%s", PQerrorMessage(pset.db));
  				PQclear(svptres);
  				OK = false;
  
  				PQclear(results);
  				ResetCancelConn();
  				goto sendquery_cleanup;
  			}
  			PQclear(svptres);
  		}
  	}
  
  	PQclear(results);
  
  	/* Possible microtiming output */
  	if (pset.timing)
  		printf(_("Time: %.3f ms\n"), elapsed_msec);
  
  	/* check for events that may occur during query execution */
  
  	if (pset.encoding != PQclientEncoding(pset.db) &&
  		PQclientEncoding(pset.db) >= 0)
  	{
  		/* track effects of SET CLIENT_ENCODING */
  		pset.encoding = PQclientEncoding(pset.db);
  		pset.popt.topt.encoding = pset.encoding;
  		SetVariable(pset.vars, "ENCODING",
  					pg_encoding_to_char(pset.encoding));
  	}
  
  	PrintNotifications();
  
  	/* perform cleanup that should occur after any attempted query */
  
  sendquery_cleanup:
  
  	/* reset \g's output-to-filename trigger */
  	if (pset.gfname)
  	{
  		free(pset.gfname);
  		pset.gfname = NULL;
  	}
  
  	/* reset \gset trigger */
  	if (pset.gset_prefix)
  	{
  		free(pset.gset_prefix);
  		pset.gset_prefix = NULL;
  	}
  
  	return OK;
  }
  
  
  /*
   * ExecQueryUsingCursor: run a SELECT-like query using a cursor
   *
   * This feature allows result sets larger than RAM to be dealt with.
   *
   * Returns true if the query executed successfully, false otherwise.
   *
   * If pset.timing is on, total query time (exclusive of result-printing) is
   * stored into *elapsed_msec.
   */
  static bool
  ExecQueryUsingCursor(const char *query, double *elapsed_msec)
  {
  	bool		OK = true;
  	PGresult   *results;
  	PQExpBufferData buf;
  	printQueryOpt my_popt = pset.popt;
  	FILE	   *queryFout_copy = pset.queryFout;
  	bool		queryFoutPipe_copy = pset.queryFoutPipe;
  	bool		started_txn = false;
  	bool		did_pager = false;
  	int			ntuples;
  	int			fetch_count;
  	char		fetch_cmd[64];
  	instr_time	before,
  				after;
  	int			flush_error;
  
  	*elapsed_msec = 0;
  
  	/* initialize print options for partial table output */
  	my_popt.topt.start_table = true;
  	my_popt.topt.stop_table = false;
  	my_popt.topt.prior_records = 0;
  
  	if (pset.timing)
  		INSTR_TIME_SET_CURRENT(before);
  
  	/* if we're not in a transaction, start one */
  	if (PQtransactionStatus(pset.db) == PQTRANS_IDLE)
  	{
  		results = PQexec(pset.db, "BEGIN");
  		OK = AcceptResult(results) &&
  			(PQresultStatus(results) == PGRES_COMMAND_OK);
  		PQclear(results);
  		if (!OK)
  			return false;
  		started_txn = true;
  	}
  
  	/* Send DECLARE CURSOR */
  	initPQExpBuffer(&buf);
  	appendPQExpBuffer(&buf, "DECLARE _psql_cursor NO SCROLL CURSOR FOR\n%s",
  					  query);
  
  	results = PQexec(pset.db, buf.data);
  	OK = AcceptResult(results) &&
  		(PQresultStatus(results) == PGRES_COMMAND_OK);
  	PQclear(results);
  	termPQExpBuffer(&buf);
  	if (!OK)
  		goto cleanup;
  
  	if (pset.timing)
  	{
  		INSTR_TIME_SET_CURRENT(after);
  		INSTR_TIME_SUBTRACT(after, before);
  		*elapsed_msec += INSTR_TIME_GET_MILLISEC(after);
  	}
  
  	/*
  	 * In \gset mode, we force the fetch count to be 2, so that we will throw
  	 * the appropriate error if the query returns more than one row.
  	 */
  	if (pset.gset_prefix)
  		fetch_count = 2;
  	else
  		fetch_count = pset.fetch_count;
  
  	snprintf(fetch_cmd, sizeof(fetch_cmd),
  			 "FETCH FORWARD %d FROM _psql_cursor",
  			 fetch_count);
  
  	/* prepare to write output to \g argument, if any */
  	if (pset.gfname)
  	{
  		/* keep this code in sync with PrintQueryTuples */
  		pset.queryFout = stdout;	/* so it doesn't get closed */
  
  		/* open file/pipe */
  		if (!setQFout(pset.gfname))
  		{
  			pset.queryFout = queryFout_copy;
  			pset.queryFoutPipe = queryFoutPipe_copy;
  			OK = false;
  			goto cleanup;
  		}
  	}
  
  	/* clear any pre-existing error indication on the output stream */
  	clearerr(pset.queryFout);
  
  	for (;;)
  	{
  		if (pset.timing)
  			INSTR_TIME_SET_CURRENT(before);
  
  		/* get fetch_count tuples at a time */
  		results = PQexec(pset.db, fetch_cmd);
  
  		if (pset.timing)
  		{
  			INSTR_TIME_SET_CURRENT(after);
  			INSTR_TIME_SUBTRACT(after, before);
  			*elapsed_msec += INSTR_TIME_GET_MILLISEC(after);
  		}
  
  		if (PQresultStatus(results) != PGRES_TUPLES_OK)
  		{
  			/* shut down pager before printing error message */
  			if (did_pager)
  			{
  				ClosePager(pset.queryFout);
  				pset.queryFout = queryFout_copy;
  				pset.queryFoutPipe = queryFoutPipe_copy;
  				did_pager = false;
  			}
  
  			OK = AcceptResult(results);
  			Assert(!OK);
  			PQclear(results);
  			break;
  		}
  
  		if (pset.gset_prefix)
  		{
  			/* StoreQueryTuple will complain if not exactly one row */
  			OK = StoreQueryTuple(results);
  			PQclear(results);
  			break;
  		}
  
  		ntuples = PQntuples(results);
  
  		if (ntuples < fetch_count)
  		{
  			/* this is the last result set, so allow footer decoration */
  			my_popt.topt.stop_table = true;
  		}
  		else if (pset.queryFout == stdout && !did_pager)
  		{
  			/*
  			 * If query requires multiple result sets, hack to ensure that
  			 * only one pager instance is used for the whole mess
  			 */
  			pset.queryFout = PageOutput(100000, my_popt.topt.pager);
  			did_pager = true;
  		}
  
  		printQuery(results, &my_popt, pset.queryFout, pset.logfile);
  
  		PQclear(results);
  
  		/* after the first result set, disallow header decoration */
  		my_popt.topt.start_table = false;
  		my_popt.topt.prior_records += ntuples;
  
  		/*
  		 * Make sure to flush the output stream, so intermediate results are
  		 * visible to the client immediately.  We check the results because if
  		 * the pager dies/exits/etc, there's no sense throwing more data at
  		 * it.
  		 */
  		flush_error = fflush(pset.queryFout);
  
  		/*
  		 * Check if we are at the end, if a cancel was pressed, or if there
  		 * were any errors either trying to flush out the results, or more
  		 * generally on the output stream at all.  If we hit any errors
  		 * writing things to the stream, we presume $PAGER has disappeared and
  		 * stop bothering to pull down more data.
  		 */
  		if (ntuples < fetch_count || cancel_pressed || flush_error ||
  			ferror(pset.queryFout))
  			break;
  	}
  
  	/* close \g argument file/pipe, restore old setting */
  	if (pset.gfname)
  	{
  		/* keep this code in sync with PrintQueryTuples */
  		setQFout(NULL);
  
  		pset.queryFout = queryFout_copy;
  		pset.queryFoutPipe = queryFoutPipe_copy;
  	}
  	else if (did_pager)
  	{
  		ClosePager(pset.queryFout);
  		pset.queryFout = queryFout_copy;
  		pset.queryFoutPipe = queryFoutPipe_copy;
  	}
  
  cleanup:
  	if (pset.timing)
  		INSTR_TIME_SET_CURRENT(before);
  
  	/*
  	 * We try to close the cursor on either success or failure, but on failure
  	 * ignore the result (it's probably just a bleat about being in an aborted
  	 * transaction)
  	 */
  	results = PQexec(pset.db, "CLOSE _psql_cursor");
  	if (OK)
  	{
  		OK = AcceptResult(results) &&
  			(PQresultStatus(results) == PGRES_COMMAND_OK);
  	}
  	PQclear(results);
  
  	if (started_txn)
  	{
  		results = PQexec(pset.db, OK ? "COMMIT" : "ROLLBACK");
  		OK &= AcceptResult(results) &&
  			(PQresultStatus(results) == PGRES_COMMAND_OK);
  		PQclear(results);
  	}
  
  	if (pset.timing)
  	{
  		INSTR_TIME_SET_CURRENT(after);
  		INSTR_TIME_SUBTRACT(after, before);
  		*elapsed_msec += INSTR_TIME_GET_MILLISEC(after);
  	}
  
  	return OK;
  }
  
  
  /*
   * Advance the given char pointer over white space and SQL comments.
   */
  static const char *
  skip_white_space(const char *query)
  {
  	int			cnestlevel = 0; /* slash-star comment nest level */
  
  	while (*query)
  	{
  		int			mblen = PQmblen(query, pset.encoding);
  
  		/*
  		 * Note: we assume the encoding is a superset of ASCII, so that for
  		 * example "query[0] == '/'" is meaningful.  However, we do NOT assume
  		 * that the second and subsequent bytes of a multibyte character
  		 * couldn't look like ASCII characters; so it is critical to advance
  		 * by mblen, not 1, whenever we haven't exactly identified the
  		 * character we are skipping over.
  		 */
  		if (isspace((unsigned char) *query))
  			query += mblen;
  		else if (query[0] == '/' && query[1] == '*')
  		{
  			cnestlevel++;
  			query += 2;
  		}
  		else if (cnestlevel > 0 && query[0] == '*' && query[1] == '/')
  		{
  			cnestlevel--;
  			query += 2;
  		}
  		else if (cnestlevel == 0 && query[0] == '-' && query[1] == '-')
  		{
  			query += 2;
  
  			/*
  			 * We have to skip to end of line since any slash-star inside the
  			 * -- comment does NOT start a slash-star comment.
  			 */
  			while (*query)
  			{
  				if (*query == '\n')
  				{
  					query++;
  					break;
  				}
  				query += PQmblen(query, pset.encoding);
  			}
  		}
  		else if (cnestlevel > 0)
  			query += mblen;
  		else
  			break;				/* found first token */
  	}
  
  	return query;
  }
  
  
  /*
   * Check whether a command is one of those for which we should NOT start
   * a new transaction block (ie, send a preceding BEGIN).
   *
   * These include the transaction control statements themselves, plus
   * certain statements that the backend disallows inside transaction blocks.
   */
  static bool
  command_no_begin(const char *query)
  {
  	int			wordlen;
  
  	/*
  	 * First we must advance over any whitespace and comments.
  	 */
  	query = skip_white_space(query);
  
  	/*
  	 * Check word length (since "beginx" is not "begin").
  	 */
  	wordlen = 0;
  	while (isalpha((unsigned char) query[wordlen]))
  		wordlen += PQmblen(&query[wordlen], pset.encoding);
  
  	/*
  	 * Transaction control commands.  These should include every keyword that
  	 * gives rise to a TransactionStmt in the backend grammar, except for the
  	 * savepoint-related commands.
  	 *
  	 * (We assume that START must be START TRANSACTION, since there is
  	 * presently no other "START foo" command.)
  	 */
  	if (wordlen == 5 && pg_strncasecmp(query, "abort", 5) == 0)
  		return true;
  	if (wordlen == 5 && pg_strncasecmp(query, "begin", 5) == 0)
  		return true;
  	if (wordlen == 5 && pg_strncasecmp(query, "start", 5) == 0)
  		return true;
  	if (wordlen == 6 && pg_strncasecmp(query, "commit", 6) == 0)
  		return true;
  	if (wordlen == 3 && pg_strncasecmp(query, "end", 3) == 0)
  		return true;
  	if (wordlen == 8 && pg_strncasecmp(query, "rollback", 8) == 0)
  		return true;
  	if (wordlen == 7 && pg_strncasecmp(query, "prepare", 7) == 0)
  	{
  		/* PREPARE TRANSACTION is a TC command, PREPARE foo is not */
  		query += wordlen;
  
  		query = skip_white_space(query);
  
  		wordlen = 0;
  		while (isalpha((unsigned char) query[wordlen]))
  			wordlen += PQmblen(&query[wordlen], pset.encoding);
  
  		if (wordlen == 11 && pg_strncasecmp(query, "transaction", 11) == 0)
  			return true;
  		return false;
  	}
  
  	/*
  	 * Commands not allowed within transactions.  The statements checked for
  	 * here should be exactly those that call PreventTransactionChain() in the
  	 * backend.
  	 */
  	if (wordlen == 6 && pg_strncasecmp(query, "vacuum", 6) == 0)
  		return true;
  	if (wordlen == 7 && pg_strncasecmp(query, "cluster", 7) == 0)
  	{
  		/* CLUSTER with any arguments is allowed in transactions */
  		query += wordlen;
  
  		query = skip_white_space(query);
  
  		if (isalpha((unsigned char) query[0]))
  			return false;		/* has additional words */
  		return true;			/* it's CLUSTER without arguments */
  	}
  
  	if (wordlen == 6 && pg_strncasecmp(query, "create", 6) == 0)
  	{
  		query += wordlen;
  
  		query = skip_white_space(query);
  
  		wordlen = 0;
  		while (isalpha((unsigned char) query[wordlen]))
  			wordlen += PQmblen(&query[wordlen], pset.encoding);
  
  		if (wordlen == 8 && pg_strncasecmp(query, "database", 8) == 0)
  			return true;
  		if (wordlen == 10 && pg_strncasecmp(query, "tablespace", 10) == 0)
  			return true;
  
  		/* CREATE [UNIQUE] INDEX CONCURRENTLY isn't allowed in xacts */
  		if (wordlen == 6 && pg_strncasecmp(query, "unique", 6) == 0)
  		{
  			query += wordlen;
  
  			query = skip_white_space(query);
  
  			wordlen = 0;
  			while (isalpha((unsigned char) query[wordlen]))
  				wordlen += PQmblen(&query[wordlen], pset.encoding);
  		}
  
  		if (wordlen == 5 && pg_strncasecmp(query, "index", 5) == 0)
  		{
  			query += wordlen;
  
  			query = skip_white_space(query);
  
  			wordlen = 0;
  			while (isalpha((unsigned char) query[wordlen]))
  				wordlen += PQmblen(&query[wordlen], pset.encoding);
  
  			if (wordlen == 12 && pg_strncasecmp(query, "concurrently", 12) == 0)
  				return true;
  		}
  
  		return false;
  	}
  
  	if (wordlen == 5 && pg_strncasecmp(query, "alter", 5) == 0)
  	{
  		query += wordlen;
  
  		query = skip_white_space(query);
  
  		wordlen = 0;
  		while (isalpha((unsigned char) query[wordlen]))
  			wordlen += PQmblen(&query[wordlen], pset.encoding);
  
  		/* ALTER SYSTEM isn't allowed in xacts */
  		if (wordlen == 6 && pg_strncasecmp(query, "system", 6) == 0)
  			return true;
  
  		return false;
  	}
  
  	/*
  	 * Note: these tests will match DROP SYSTEM and REINDEX TABLESPACE, which
  	 * aren't really valid commands so we don't care much. The other four
  	 * possible matches are correct.
  	 */
  	if ((wordlen == 4 && pg_strncasecmp(query, "drop", 4) == 0) ||
  		(wordlen == 7 && pg_strncasecmp(query, "reindex", 7) == 0))
  	{
  		query += wordlen;
  
  		query = skip_white_space(query);
  
  		wordlen = 0;
  		while (isalpha((unsigned char) query[wordlen]))
  			wordlen += PQmblen(&query[wordlen], pset.encoding);
  
  		if (wordlen == 8 && pg_strncasecmp(query, "database", 8) == 0)
  			return true;
  		if (wordlen == 6 && pg_strncasecmp(query, "system", 6) == 0)
  			return true;
  		if (wordlen == 10 && pg_strncasecmp(query, "tablespace", 10) == 0)
  			return true;
  		return false;
  	}
  
  	/* DISCARD ALL isn't allowed in xacts, but other variants are allowed. */
  	if (wordlen == 7 && pg_strncasecmp(query, "discard", 7) == 0)
  	{
  		query += wordlen;
  
  		query = skip_white_space(query);
  
  		wordlen = 0;
  		while (isalpha((unsigned char) query[wordlen]))
  			wordlen += PQmblen(&query[wordlen], pset.encoding);
  
  		if (wordlen == 3 && pg_strncasecmp(query, "all", 3) == 0)
  			return true;
  		return false;
  	}
  
  	return false;
  }
  
  
  /*
   * Check whether the specified command is a SELECT (or VALUES).
   */
  static bool
  is_select_command(const char *query)
  {
  	int			wordlen;
  
  	/*
  	 * First advance over any whitespace, comments and left parentheses.
  	 */
  	for (;;)
  	{
  		query = skip_white_space(query);
  		if (query[0] == '(')
  			query++;
  		else
  			break;
  	}
  
  	/*
  	 * Check word length (since "selectx" is not "select").
  	 */
  	wordlen = 0;
  	while (isalpha((unsigned char) query[wordlen]))
  		wordlen += PQmblen(&query[wordlen], pset.encoding);
  
  	if (wordlen == 6 && pg_strncasecmp(query, "select", 6) == 0)
  		return true;
  
  	if (wordlen == 6 && pg_strncasecmp(query, "values", 6) == 0)
  		return true;
  
  	return false;
  }
  
  
  /*
   * Test if the current user is a database superuser.
   *
   * Note: this will correctly detect superuserness only with a protocol-3.0
   * or newer backend; otherwise it will always say "false".
   */
  bool
  is_superuser(void)
  {
  	const char *val;
  
  	if (!pset.db)
  		return false;
  
  	val = PQparameterStatus(pset.db, "is_superuser");
  
  	if (val && strcmp(val, "on") == 0)
  		return true;
  
  	return false;
  }
  
  
  /*
   * Test if the current session uses standard string literals.
   *
   * Note: With a pre-protocol-3.0 connection this will always say "false",
   * which should be the right answer.
   */
  bool
  standard_strings(void)
  {
  	const char *val;
  
  	if (!pset.db)
  		return false;
  
  	val = PQparameterStatus(pset.db, "standard_conforming_strings");
  
  	if (val && strcmp(val, "on") == 0)
  		return true;
  
  	return false;
  }
  
  
  /*
   * Return the session user of the current connection.
   *
   * Note: this will correctly detect the session user only with a
   * protocol-3.0 or newer backend; otherwise it will return the
   * connection user.
   */
  const char *
  session_username(void)
  {
  	const char *val;
  
  	if (!pset.db)
  		return NULL;
  
  	val = PQparameterStatus(pset.db, "session_authorization");
  	if (val)
  		return val;
  	else
  		return PQuser(pset.db);
  }
  
  
  /* expand_tilde
   *
   * substitute '~' with HOME or '~username' with username's home dir
   *
   */
  void
  expand_tilde(char **filename)
  {
  	if (!filename || !(*filename))
  		return;
  
  	/*
  	 * WIN32 doesn't use tilde expansion for file names. Also, it uses tilde
  	 * for short versions of long file names, though the tilde is usually
  	 * toward the end, not at the beginning.
  	 */
  #ifndef WIN32
  
  	/* try tilde expansion */
  	if (**filename == '~')
  	{
  		char	   *fn;
  		char		oldp,
  				   *p;
  		struct passwd *pw;
  		char		home[MAXPGPATH];
  
  		fn = *filename;
  		*home = '\0';
  
  		p = fn + 1;
  		while (*p != '/' && *p != '\0')
  			p++;
  
  		oldp = *p;
  		*p = '\0';
  
  		if (*(fn + 1) == '\0')
  			get_home_path(home);	/* ~ or ~/ only */
  		else if ((pw = getpwnam(fn + 1)) != NULL)
  			strlcpy(home, pw->pw_dir, sizeof(home));	/* ~user */
  
  		*p = oldp;
  		if (strlen(home) != 0)
  		{
  			char	   *newfn;
  
  			newfn = psprintf("%s%s", home, p);
  			free(fn);
  			*filename = newfn;
  		}
  	}
  #endif
  
  	return;
  }
  