Proposal for Allow postgresql.conf values to be changed via SQL

*** a/src/bin/initdb/initdb.c
--- b/src/bin/initdb/initdb.c
***************
*** 177,182 **** static const char *backend_options = "--single -F -O -c search_path=pg_catalog -
--- 177,183 ----
  static char bin_path[MAXPGPATH];
  static char backend_exec[MAXPGPATH];
  
+ static char * make_absolute_path(const char *path);
  static void *pg_malloc(size_t size);
  static char *pg_strdup(const char *s);
  static char **replace_token(char **lines,
***************
*** 1163,1168 **** setup_config(void)
--- 1164,1171 ----
  	char		repltok[MAXPGPATH];
  	char		path[MAXPGPATH];
  	const char *default_timezone;
+ 	char *abs_data_dir;
+ 	FILE	   *autofile;
  
  	fputs(_("creating configuration files ... "), stdout);
  	fflush(stdout);
***************
*** 1245,1255 **** setup_config(void)
--- 1248,1285 ----
  		conflines = replace_token(conflines, "#log_timezone = 'GMT'", repltok);
  	}
  
+ 	abs_data_dir = make_absolute_path(pg_data);
+ 
+ 	snprintf(repltok, sizeof(repltok), "include_dir = '%s/config_dir'",
+ 			 abs_data_dir);
+ 	conflines = replace_token(conflines, "#include_dir = 'conf.d'", repltok);
+ 
  	snprintf(path, sizeof(path), "%s/postgresql.conf", pg_data);
  
  	writefile(path, conflines);
  	chmod(path, S_IRUSR | S_IWUSR);
  
+ 	/*create a .auto for conf file*/
+ 	sprintf(path, "%s/config_dir/postgresql.auto.conf", pg_data);
+ 	autofile = fopen(path, PG_BINARY_W);
+ 	if (autofile == NULL)
+ 	{
+ 		fprintf(stderr, _("%s: could not open file \"%s\" for writing: %s\n"),
+ 				progname, path, strerror(errno));
+ 		exit_nicely();
+ 	}
+ 
+ 	
+ 	if (fclose(autofile))
+ 	{
+ 		fprintf(stderr, _("%s: could not write file \"%s\": %s\n"),
+ 				progname, path, strerror(errno));
+ 		exit_nicely();
+ 	}
+ 
+ 	chmod(path, S_IRUSR | S_IWUSR);
+ 
+ 
  	free(conflines);
  
  
***************
*** 2823,2828 **** check_need_password(const char *authmethodlocal, const char *authmethodhost)
--- 2853,2934 ----
  	}
  }
  
+ /*
+  * If the given pathname isn't already absolute, make it so, interpreting
+  * it relative to the current working directory.
+  *
+  * Also canonicalizes the path.  The result is always a malloc'd copy.
+  *
+  */
+ static char *
+ make_absolute_path(const char *path)
+ {
+ 	char	   *new;
+ 
+ 	/* Returning null for null input is convenient for some callers */
+ 	if (path == NULL)
+ 		return NULL;
+ 
+ 	if (!is_absolute_path(path))
+ 	{
+ 		char	   *buf;
+ 		size_t		buflen;
+ 
+ 		buflen = MAXPGPATH;
+ 		for (;;)
+ 		{
+ 			buf = malloc(buflen);
+ 			if (!buf)
+ 			{
+ 				fprintf(stderr, _("%s: Memory allocation failed\n"),
+ 				progname);
+ 				exit_nicely();
+ 			}
+ 
+ 			if (getcwd(buf, buflen))
+ 				break;
+ 			else if (errno == ERANGE)
+ 			{
+ 				free(buf);
+ 				buflen *= 2;
+ 				continue;
+ 			}
+ 			else
+ 			{
+ 				free(buf);
+ 				fprintf(stderr, _("%s: could not get current working directory\n"),
+ 				progname);
+ 				exit_nicely();
+ 			}
+ 		}
+ 
+ 		new = malloc(strlen(buf) + strlen(path) + 2);
+ 		if (!new)
+ 		{
+ 			fprintf(stderr, _("%s: Memory allocation failed\n"),
+ 			progname);
+ 			exit_nicely();
+ 		}
+ 		sprintf(new, "%s/%s", buf, path);
+ 		free(buf);
+ 	}
+ 	else
+ 	{
+ 		new = strdup(path);
+ 		if (!new)
+ 		{
+ 			fprintf(stderr, _("%s: Memory allocation failed\n"),
+ 			progname);
+ 			exit_nicely();
+ 		}
+ 	}
+ 
+ 	/* Make sure punctuation is canonical, too */
+ 	canonicalize_path(new);
+ 
+ 	return new;
+ }
+ 
  int
  main(int argc, char *argv[])
  {
***************
*** 2887,2893 **** main(int argc, char *argv[])
  		"base",
  		"base/1",
  		"pg_tblspc",
! 		"pg_stat_tmp"
  	};
  
  	progname = get_progname(argv[0]);
--- 2993,3000 ----
  		"base",
  		"base/1",
  		"pg_tblspc",
! 		"pg_stat_tmp",
! 		"config_dir"
  	};
  
  	progname = get_progname(argv[0]);

*** a/src/backend/commands/dbcommands.c
--- b/src/backend/commands/dbcommands.c
***************
*** 58,63 ****
--- 58,80 ----
  #include "utils/snapmgr.h"
  #include "utils/syscache.h"
  #include "utils/tqual.h"
+ #include "utils/guc_tables.h"
+ 
+ 
+ /*lock file used in edit postgresql.conf.auto*/
+ struct lock_file 
+ {
+ 	int fd;
+ 	char filename[MAXPGPATH];
+ };
+ 
+ 
+ struct strbuf 
+ {
+ 	size_t len;
+ 	char *buf;
+ };
+ 
  
  
  typedef struct
***************
*** 1434,1439 **** AlterDatabaseSet(AlterDatabaseSetStmt *stmt)
--- 1451,1827 ----
  
  
  /*
+  * EDIT .AUTO.CONF FILE WITH FUNCTION pg_change_conf(key,value)...
+  */
+ 
+ /*create a .lock file for .auto.conf file so that it act as an lock to prevent concurrent edit on .auto.conf file*/
+ static int lock_confile(struct lock_file *lk, const char *path, int flags)
+ {    	
+ 	int			ntries = 0;
+ 	strcpy(lk->filename, path);
+ 	strcat(lk->filename, CONF_LOCK_POSTFIX);
+ tryAgain:	
+ 	lk->fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666);
+ 	if (0 > lk->fd) 
+ 	{
+ 		/*
+ 		 * Couldn't create the lock file. Probably it already exists. If so wait for some time
+ 		 */
+ 
+ 		ntries++;
+ 		if ((errno != EEXIST && errno != EACCES) || ntries > 100)
+ 		{
+ 			if (errno != EEXIST)
+ 			{
+ 				ereport(LOG,
+ 					(errcode_for_file_access(),
+ 					 errmsg("could not create lock file \"%s\": %m",
+ 							lk->filename)));
+ 			}
+ 			else
+ 			{
+ 				ereport(LOG,
+ 					(errcode_for_file_access(),
+ 					 errmsg("could not create lock file \"%s\": %m ",lk->filename),
+ 					 errhint("May be too many concurrent edit into file happening, please wait!! and retry"
+ 					 "or .lock is file accidently left there please clean the file from config_dir")));
+ 			}
+ 			
+ 			lk->filename[0] = 0;
+ 		}
+ 		else
+ 		{
+ 			pg_usleep(100000); /*in total wait for 10sec*/
+ 			goto tryAgain;
+ 		}	
+ 	}
+ 
+ 	return lk->fd;
+ }
+ 
+ /*function to close the .lock file*/
+ int close_lock_file(struct lock_file *lk)
+ {
+ 	int fd = lk->fd;
+ 	lk->fd = -1;
+ 	return close(fd);
+ }
+ 
+ /*function to commit the changes done on element of .auto.conf file */
+ /* here we rename .lock to .auto.conf hence commit the changes to .auto.conf file */
+ int commit_lock_file(struct lock_file *lk)
+ {
+ 	char result_file[MAXPGPATH];
+ 	size_t i;
+ 	if (lk->fd >= 0 && close_lock_file(lk))
+ 		return -1;
+ 	strcpy(result_file, lk->filename);
+ 	i = strlen(result_file) - 5; /* remove .lock charecters */
+ 	result_file[i] = 0;
+ 	if (rename(lk->filename, result_file))
+ 		return -1;
+ 	lk->filename[0] = 0;
+ 	return 0;
+ }
+ 
+ 
+ /*On some error we need to rollback the changes we do this by removing .lock file*/
+ void rollback_lock_file(struct lock_file *lk)
+ {
+ 	if (lk->filename[0]) 
+ 	{
+ 		if (lk->fd >= 0)
+ 		{
+ 			/*cloase the file*/
+ 			close(lk->fd);
+ 		}
+ 
+ 		/*now remove the file*/
+ 		unlink(lk->filename);
+ 	}
+ 	
+ 	lk->filename[0] = 0;
+ }
+ 
+ 
+ /*
+  * get the lines from a text file
+  */
+ static char **
+ readfile(const char *path)
+ {
+ 	FILE	   *infile;
+ 	int			maxlength = 1,
+ 				linelen = 0;
+ 	int			nlines = 0;
+ 	char	  **result;
+ 	char	   *buffer;
+ 	int			c;
+ 
+ 	if ((infile = fopen(path, "r")) == NULL)
+ 	{
+ 		ereport(ERROR,
+ 			(errmsg("failed to read into to \"postgresql.auto.conf\" file")));
+ 		/*throw error*/
+ 	}
+ 
+ 	/* pass over the file twice - the first time to size the result */
+ 
+ 	while ((c = fgetc(infile)) != EOF)
+ 	{
+ 		linelen++;
+ 		if (c == '\n')
+ 		{
+ 			nlines++;
+ 			if (linelen > maxlength)
+ 				maxlength = linelen;
+ 			linelen = 0;
+ 		}
+ 	}
+ 
+ 	/* handle last line without a terminating newline (yuck) */
+ 	if (linelen)
+ 		nlines++;
+ 	if (linelen > maxlength)
+ 		maxlength = linelen;
+ 
+ 	/* set up the result and the line buffer */
+ 	result = (char **) palloc((nlines + 1) * sizeof(char *));
+ 	buffer = (char *) palloc(maxlength + 1);
+ 
+ 	/* now reprocess the file and store the lines */
+ 	rewind(infile);
+ 	nlines = 0;
+ 	while (fgets(buffer, maxlength + 1, infile) != NULL)
+ 		result[nlines++] = pstrdup(buffer);
+ 
+ 	fclose(infile);
+ 	pfree(buffer);
+ 	result[nlines] = NULL;
+ 
+ 	return result;
+ }
+ 
+ /*
+  * write an array of lines to a file 
+  * used to write the in-memory of .auto.conf elements to .lock file
+  *
+  */
+ static void
+ writeAutoConffile(int fd, char **lines)
+ {
+ 	char	  **line;
+ 
+ 	for (line = lines; *line != NULL; line++)
+ 	{
+ 		if (write(fd, *line, strlen(*line)) < 0)
+ 		{
+ 			ereport(ERROR,
+ 			(errmsg("failed to write into to \"postgresql.auto.conf.lock\" file")));
+ 			/*throw error*/
+ 		}
+ 		pfree(*line);
+ 	}
+ 
+ 	if (pg_fsync(fd) != 0)
+ 	{
+ 		ereport(ERROR,
+ 				(errcode_for_file_access(),
+ 				 errmsg("could not write to file \"postgresql.auto.conf.lock\": %m")));
+ 	}
+ 
+ }
+ 
+ /*
+  * make the changes requested by pg_change_conf() In-Memory by replacing the older content.
+  * If not already exist add the new (key,value) to end of list.
+  */
+ static char **
+ replace_autoline(char **lines,unsigned int repl_lineno , const char *replacement,
+ 					bool hasmatch)
+ {
+ 	int			numlines = 1;
+ 	int			i;
+ 	char	  **result;
+ 	int		replen;
+ 	char	   *newline;
+ 
+ 	for (i = 0; lines[i]; i++)
+ 	{
+ 		numlines++;
+ 	}
+ 
+ 	if (!hasmatch)
+ 	{
+ 	       /*key not found need to add one more line at the end*/
+ 		result = (char **) palloc0((numlines + 1)* sizeof(char *));
+ 		repl_lineno++;
+ 	}
+ 	else
+ 	{
+ 		result = (char **) palloc0(numlines * sizeof(char *));
+ 	}	
+ 
+ 	replen = strlen(replacement);
+ 	
+ 	for (i = 0; i < numlines; i++)
+ 	{
+ 		/* just copy pointer if NULL or no change needed */
+ 		if (lines[i] == NULL || (i != repl_lineno - 1))
+ 		{
+ 			result[i] = lines[i];
+ 			continue;
+ 		}
+ 
+ 		/* if we get here a change is needed - set up new line */
+ 
+ 		newline = (char *) palloc(replen + 1);
+ 
+ 		strcpy(newline, replacement);
+ 		result[i] = newline;
+ 	}
+ 
+ 	if (!hasmatch)
+ 	{
+ 		/*key not found in file add it to end of (key,value) list*/
+ 		newline = (char *) palloc(replen + 1);
+ 
+ 		strcpy(newline, replacement);
+ 		result[i - 1] = newline;
+ 	}
+ 	
+ 	return result;
+ }
+ 
+ 
+ /*main function which edit .auto.file with given (key,value) input*/
+ void set_config_file(VariableSetStmt *setstmt)
+ {   
+        struct strbuf sb;
+ 	char *key;
+ 	char *value;
+ 	char	  **conflines;
+ 	struct lock_file *lock = NULL;
+ 	int fd = -1, lineno = 0;
+ 	FILE	   *infile;
+ 	struct config_generic *record;
+ 	char		abs_path[MAXPGPATH];
+ 	bool OK;
+ 	bool hasmatch;
+ 
+ 
+ 	if  (IsTransactionBlock())
+ 	{
+ 		ereport(ERROR,
+ 		(errcode(ERRCODE_ACTIVE_SQL_TRANSACTION),
+ 		 errmsg("cannot modify autoconf file inside a transaction")));
+ 	}
+ 
+ 	if (!superuser())
+ 	{
+ 		ereport(ERROR,
+ 					(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+ 					 (errmsg("must be superuser to edit postgresql.conf"))));
+ 	}
+ 	
+ 	/*1. validate the key and value and then make the conf info into (key, value, comment) pair*/
+ 
+ 	key = pstrdup(setstmt->name); 	
+ 	value = ExtractSetVariableArgs(setstmt);
+ 	
+ 	record = validate_conf_option(key,value);
+ 
+ 	if (!record)
+ 	{
+ 		ereport(ERROR,
+ 		(errmsg("evaluation of config:values failed")));
+ 	}
+ 	
+ 	sb.len = strlen(key);
+ 	sb.len += strlen(value);
+ 	sb.buf = palloc(sb.len + 100);
+ 
+     	if (record->vartype == PGC_STRING)
+ 	{
+ 		snprintf(sb.buf, sb.len + 100, "%s = '%s' \n", key, value);
+ 	}
+ 	else
+ 	{
+ 		snprintf(sb.buf, sb.len + 100, "%s = %s \n", key, value);
+ 	}
+ 	
+ 	/*2. create the lock file */
+ 
+ 	join_path_components(abs_path, data_directory, AutoConfigFileName);
+ 	canonicalize_path(abs_path);
+ 
+ 	PG_TRY();
+ 	{	
+ 		lock = palloc0(sizeof(struct lock_file));
+ 
+ 		/*take the .lock file so other backends are restricted from access*/
+ 		fd = lock_confile(lock, abs_path, 0);
+ 		if (fd < 0) 
+ 		{
+ 			ereport(ERROR,
+ 				(errmsg("lock file creation failed")));	}
+ 
+ 		/*open .auto.conf file*/
+ 		infile = fopen(abs_path, "r");
+ 		if (infile == NULL) 
+ 		{
+ 			ereport(ERROR,
+ 				(errmsg("failed to open postgresql.auto.conf file")));
+ 		} 
+ 		
+ 
+ 		/*3. read from the auto.conf file and write new contents to .lock file */
+ 		conflines = readfile(abs_path);
+ 
+ 		OK = ParseAutoConfigFp(infile, abs_path, key, &lineno, -1, LOG, &hasmatch);
+ 		if (!OK)
+ 		{			
+ 			ereport(ERROR,
+ 				(errmsg("parsing failed for postgresql.auto.conf file")));
+ 			/*throw error*/
+ 		}
+ 
+ 		fclose(infile);
+ 		conflines = replace_autoline(conflines, lineno - 1, sb.buf, hasmatch);
+ 
+ 		/*Write the New contents to .lock file*/
+ 		writeAutoConffile(fd, conflines);
+ 
+ 
+ 		/*4. commit the .lock file;  here rename the lock file to .auto.conf file*/
+ 		
+ 		if (commit_lock_file(lock) < 0) 
+ 		{ 			
+ 			ereport(ERROR,
+ 			(errmsg("commiting lock.postgresql.auto.conf failed")));
+ 		}
+ 	}
+ 	PG_CATCH()
+ 	{
+ 		if (lock)
+ 		{
+ 			/*remove the .lock file*/
+ 			rollback_lock_file(lock);
+ 			pfree(lock);
+ 		}
+ 
+ 		PG_RE_THROW();
+ 	}	
+ 	PG_END_TRY();
+ 	
+ 	pfree(lock);
+ 	return;				
+ }
+ 
+ 
+ 
+ 
+ /*
   * ALTER DATABASE name OWNER TO newowner
   */
  void
*** a/src/backend/postmaster/postmaster.c
--- b/src/backend/postmaster/postmaster.c
***************
*** 507,512 **** PostmasterMain(int argc, char *argv[])
--- 507,513 ----
  	char	   *userDoption = NULL;
  	bool		listen_addr_saved = false;
  	int			i;
+ 	char		conf_lock_file[MAXPGPATH];
  
  	MyProcPid = PostmasterPid = getpid();
  
***************
*** 1163,1168 **** PostmasterMain(int argc, char *argv[])
--- 1164,1176 ----
  	 */
  	RemovePgTempFiles();
  
+ 	/*Remove .auto.conf.lock file make be left over from last crash*/
+ 
+ 	/*get .auto.conf.lock file name */
+ 	strcpy(conf_lock_file, AutoConfigFileName);
+ 	strcat(conf_lock_file, CONF_LOCK_POSTFIX);
+ 	unlink(conf_lock_file);
+ 
  	/*
  	 * Remember postmaster startup time
  	 */
*** a/src/backend/replication/basebackup.c
--- b/src/backend/replication/basebackup.c
***************
*** 581,586 **** sendDir(char *path, int basepathlen, bool sizeonly)
--- 581,592 ----
  					strlen(PG_TEMP_FILE_PREFIX)) == 0)
  			continue;
  
+ 		/*skip lock files used in postgresql.auto.conf edit*/		
+ 		if (strncmp(de->d_name,
+ 					"postgresql.auto.conf.lock",
+ 					strlen("postgresql.auto.conf.lock")) == 0)
+ 			continue;
+ 
  		/*
  		 * If there's a backup_label file, it belongs to a backup started by
  		 * the user with pg_start_backup(). It is *not* correct for this
*** a/src/backend/tcop/utility.c
--- b/src/backend/tcop/utility.c
***************
*** 1061,1067 **** standard_ProcessUtility(Node *parsetree,
  		case T_AlterDatabaseSetStmt:
  			/* no event triggers for global objects */
  			AlterDatabaseSet((AlterDatabaseSetStmt *) parsetree);
! 			break;
  
  		case T_DropdbStmt:
  			{
--- 1061,1067 ----
  		case T_AlterDatabaseSetStmt:
  			/* no event triggers for global objects */
  			AlterDatabaseSet((AlterDatabaseSetStmt *) parsetree);
! 			break;		
  
  		case T_DropdbStmt:
  			{
***************
*** 2061,2067 **** CreateCommandTag(Node *parsetree)
  		case T_AlterDatabaseSetStmt:
  			tag = "ALTER DATABASE";
  			break;
! 
  		case T_DropdbStmt:
  			tag = "DROP DATABASE";
  			break;
--- 2061,2067 ----
  		case T_AlterDatabaseSetStmt:
  			tag = "ALTER DATABASE";
  			break;
! 			
  		case T_DropdbStmt:
  			tag = "DROP DATABASE";
  			break;
*** a/src/backend/utils/adt/misc.c
--- b/src/backend/utils/adt/misc.c
***************
*** 194,199 **** pg_reload_conf(PG_FUNCTION_ARGS)
--- 194,221 ----
  
  
  /*
+  * pg_change_conf: function to write in conf file
+  *
+  */
+ Datum
+ pg_change_conf(PG_FUNCTION_ARGS)
+ {
+ 	char	   *key = PG_GETARG_CSTRING(0);
+ 	char    *value = PG_GETARG_CSTRING(1);
+ 	VariableSetStmt setstmt;
+ 	A_Const *n = makeNode(A_Const);
+ 	n->val.type = T_String;
+ 	n->val.val.str = value;
+ 	n->location = -1;	
+ 	setstmt.type = T_VariableSetStmt;
+ 	setstmt.kind = VAR_SET_VALUE;
+ 	setstmt.name = key;
+ 	setstmt.args = list_make1(n);	
+ 	set_config_file(&setstmt);
+ 	PG_RETURN_BOOL(true);
+ }
+ 
+ /*
   * Rotate log file
   */
  Datum
*** a/src/backend/utils/misc/guc-file.l
--- b/src/backend/utils/misc/guc-file.l
***************
*** 468,473 **** GUC_flex_fatal(const char *msg)
--- 468,609 ----
  	return 0;	/* keep compiler quiet */
  }
  
+ /**
+ *  Parse the config file and return the line number which matched the key(name)
+ **/
+ 
+ bool
+ ParseAutoConfigFp(FILE *fp, const char *config_file, char * name, int *line_no, int depth, int elevel,
+ 			  			bool *hasmatch)
+ {
+ 	volatile bool OK = true;
+ 	unsigned int save_ConfigFileLineno = ConfigFileLineno;
+ 	sigjmp_buf *save_GUC_flex_fatal_jmp = GUC_flex_fatal_jmp;
+ 	sigjmp_buf	flex_fatal_jmp;
+ 	volatile YY_BUFFER_STATE lex_buffer = NULL;
+ 	int			errorcount;
+ 	int			token;
+ 
+ 	if (sigsetjmp(flex_fatal_jmp, 1) == 0)
+ 		GUC_flex_fatal_jmp = &flex_fatal_jmp;
+ 	else
+ 	{
+ 		/*
+ 		 * Regain control after a fatal, internal flex error.  It may have
+ 		 * corrupted parser state.  Consequently, abandon the file, but trust
+ 		 * that the state remains sane enough for GUC_yy_delete_buffer().
+ 		 */
+ 		elog(elevel, "%s at file \"%s\" line %u",
+ 			 GUC_flex_fatal_errmsg, config_file, ConfigFileLineno);
+ 
+ 		OK = false;
+ 		goto cleanup;
+ 	}
+ 
+ 	/*
+ 	 * Parse
+ 	 */
+ 	ConfigFileLineno = 1;
+ 	errorcount = 0;
+ 	*hasmatch = false;
+ 
+ 	lex_buffer = GUC_yy_create_buffer(fp,YY_BUF_SIZE);
+ 	GUC_yy_switch_to_buffer(lex_buffer);
+ 
+ 	/* This loop iterates once per logical line */
+ 	while ((token = GUC_yylex()))
+ 	{
+ 		char	   *opt_name = NULL;		
+ 
+ 		if (token == GUC_EOL)	/* empty or comment line */
+ 			continue;
+ 
+ 		/* first token on line is option name */
+ 		if (token != GUC_ID && token != GUC_QUALIFIED_ID)
+ 			goto parse_error;
+ 		opt_name = pstrdup(GUC_yytext);
+ 
+ 		/* next we have an optional equal sign; discard if present */
+ 		token = GUC_yylex();
+ 		if (token == GUC_EQUALS)
+ 			token = GUC_yylex();
+ 		
+ 		/* now we'd like an end of line, or possibly EOF */
+ 		token = GUC_yylex();
+ 		if (token != GUC_EOL)
+ 		{
+ 			if (token != 0)
+ 				goto parse_error;
+ 			/* treat EOF like \n for line numbering purposes, cf bug 4752 */
+ 			ConfigFileLineno++;
+ 		}
+ 
+ 		/* OK, process the option name and value */
+ 		if ((guc_name_compare(opt_name, name) == 0))
+ 		{
+ 			*hasmatch = true;
+ 			break;
+ 		}
+ 		else if (token == 0)
+ 		{
+ 			break;
+ 		}
+ 		
+ 		continue;
+ 
+ 	parse_error:
+ 		/* release storage if we allocated any on this line */
+ 		if (opt_name)
+ 			pfree(opt_name);
+ 
+ 		/* report the error */
+ 		if (token == GUC_EOL || token == 0)
+ 			ereport(elevel,
+ 					(errcode(ERRCODE_SYNTAX_ERROR),
+ 					 errmsg("syntax error in file \"%s\" line %u, near end of line",
+ 							config_file, ConfigFileLineno - 1)));
+ 		else
+ 			ereport(elevel,
+ 					(errcode(ERRCODE_SYNTAX_ERROR),
+ 					 errmsg("syntax error in file \"%s\" line %u, near token \"%s\"",
+ 							config_file, ConfigFileLineno, GUC_yytext)));
+ 		OK = false;
+ 		errorcount++;
+ 
+ 		/*
+ 		 * To avoid producing too much noise when fed a totally bogus file,
+ 		 * give up after 100 syntax errors per file (an arbitrary number).
+ 		 * Also, if we're only logging the errors at DEBUG level anyway,
+ 		 * might as well give up immediately.  (This prevents postmaster
+ 		 * children from bloating the logs with duplicate complaints.)
+ 		 */
+ 		if (errorcount >= 100 || elevel <= DEBUG1)
+ 		{
+ 			ereport(elevel,
+ 					(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+ 					 errmsg("too many syntax errors found, abandoning file \"%s\"",
+ 							config_file)));
+ 			break;
+ 		}
+ 
+ 		/* resync to next end-of-line or EOF */
+ 		while (token != GUC_EOL && token != 0)
+ 			token = GUC_yylex();
+ 		/* break out of loop on EOF */
+ 		if (token == 0)
+ 			break;
+ 	}
+ 
+ cleanup:
+ 	GUC_yy_delete_buffer(lex_buffer);
+ 	/* Each recursion level must save and restore these static variables. */
+ 	*line_no = ConfigFileLineno;
+ 	ConfigFileLineno = save_ConfigFileLineno;
+ 	GUC_flex_fatal_jmp = save_GUC_flex_fatal_jmp;
+ 	return OK;
+ }
+ 
+ 
  /*
   * Read and parse a single configuration file.  This function recurses
   * to handle "include" directives.
*** a/src/backend/utils/misc/guc.c
--- b/src/backend/utils/misc/guc.c
***************
*** 5105,5110 **** config_enum_get_options(struct config_enum * record, const char *prefix,
--- 5105,5260 ----
  	return retstr.data;
  }
  
+ /*given key and value validate the config value*/
+ 
+ struct config_generic *
+ validate_conf_option(const char *name, const char *value)
+ {
+ 	struct config_generic *record;
+ 
+ 	record = find_option(name, true, LOG);
+ 	if (record == NULL)
+ 	{
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_UNDEFINED_OBJECT),
+ 			   errmsg("unrecognized configuration parameter \"%s\"", name)));
+ 	}
+ 
+ 	if (record->context == PGC_INTERNAL)
+ 	{
+ 		ereport(ERROR,
+ 		(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
+ 		 errmsg("parameter \"%s\" cannot be changed",
+ 				name)));
+ 	}
+ 
+ 	/*
+ 	 * Evaluate value and set variable.
+ 	 */
+ 	switch (record->vartype)
+ 	{
+ 
+ 		case PGC_BOOL:
+ 			{
+ 				struct config_bool *conf = (struct config_bool *) record;
+ 				bool		newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					if (!parse_bool(value, &newval))
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						  errmsg("parameter \"%s\" requires a Boolean value",
+ 								 name)));
+ 					}
+ 					if (!call_bool_check_hook(conf, &newval, &newextra,
+ 											  PGC_S_FILE, LOG))
+ 						return NULL;
+ 				}
+ 			}
+ 			break;
+ 
+ 		case PGC_INT:
+ 			{
+ 				struct config_int *conf = (struct config_int *) record;
+ 				int			newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					const char *hintmsg;
+ 
+ 					if (!parse_int(value, &newval, conf->gen.flags, &hintmsg))
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						 errmsg("invalid value for parameter \"%s\": \"%s\"",
+ 								name, value),
+ 								 hintmsg ? errhint("%s", _(hintmsg)) : 0));
+ 					}
+ 					if (newval < conf->min || newval > conf->max)
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 								 errmsg("%d is outside the valid range for parameter \"%s\" (%d .. %d)",
+ 										newval, name, conf->min, conf->max)));
+ 					}
+ 					if (!call_int_check_hook(conf, &newval, &newextra,
+ 											 PGC_S_FILE, LOG))
+ 						return NULL;
+ 				}
+ 			}
+ 
+ 			break;
+ 
+ 		case PGC_REAL:
+ 			{
+ 				struct config_real *conf = (struct config_real *) record;
+ 				double		newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					if (!parse_real(value, &newval))
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						  errmsg("parameter \"%s\" requires a numeric value",
+ 								 name)));
+ 					}
+ 					if (newval < conf->min || newval > conf->max)
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 								 errmsg("%g is outside the valid range for parameter \"%s\" (%g .. %g)",
+ 										newval, name, conf->min, conf->max)));
+ 					}
+ 					if (!call_real_check_hook(conf, &newval, &newextra,
+ 											  PGC_S_FILE, LOG))
+ 						return NULL;
+ 				}
+ 			}	
+ 
+ 			break;
+ 
+ 		case PGC_STRING:
+ 			{
+ 				struct config_string *conf = (struct config_string *) record;
+ 				char	   *newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					/*
+ 					 * The value passed by the caller could be transient, so
+ 					 * we always strdup it.
+ 					 */
+ 					newval = guc_strdup(LOG, value);
+ 					if (newval == NULL)
+ 						return NULL;
+ 
+ 					/*
+ 					 * The only built-in "parsing" check we have is to apply
+ 					 * truncation if GUC_IS_NAME.
+ 					 */
+ 					if (conf->gen.flags & GUC_IS_NAME)
+ 						truncate_identifier(newval, strlen(newval), true);
+ 
+ 					if (!call_string_check_hook(conf, &newval, &newextra,
+ 												PGC_S_FILE, LOG))
+ 					{
+ 						free(newval);
+ 						return NULL;
+ 					}
+ 				}
+ 			}
+ 	}
+ 	
+ 	return record;
+ }
+ 
  
  /*
   * Sets option `name' to given value.
*** a/src/backend/utils/misc/postgresql.conf.sample
--- b/src/backend/utils/misc/postgresql.conf.sample
***************
*** 30,36 ****
  #                                                   h   = hours
  #                                                   d   = days
  
- 
  #------------------------------------------------------------------------------
  # FILE LOCATIONS
  #------------------------------------------------------------------------------
--- 30,35 ----
*** a/src/bin/initdb/initdb.c
--- b/src/bin/initdb/initdb.c
***************
*** 177,182 **** static const char *backend_options = "--single -F -O -c search_path=pg_catalog -
--- 177,183 ----
  static char bin_path[MAXPGPATH];
  static char backend_exec[MAXPGPATH];
  
+ static char * make_absolute_path(const char *path);
  static void *pg_malloc(size_t size);
  static char *pg_strdup(const char *s);
  static char **replace_token(char **lines,
***************
*** 1163,1168 **** setup_config(void)
--- 1164,1171 ----
  	char		repltok[MAXPGPATH];
  	char		path[MAXPGPATH];
  	const char *default_timezone;
+ 	char *abs_data_dir;
+ 	FILE	   *autofile;
  
  	fputs(_("creating configuration files ... "), stdout);
  	fflush(stdout);
***************
*** 1245,1255 **** setup_config(void)
--- 1248,1285 ----
  		conflines = replace_token(conflines, "#log_timezone = 'GMT'", repltok);
  	}
  
+ 	abs_data_dir = make_absolute_path(pg_data);
+ 
+ 	snprintf(repltok, sizeof(repltok), "include_dir = '%s/config_dir'",
+ 			 abs_data_dir);
+ 	conflines = replace_token(conflines, "#include_dir = 'conf.d'", repltok);
+ 
  	snprintf(path, sizeof(path), "%s/postgresql.conf", pg_data);
  
  	writefile(path, conflines);
  	chmod(path, S_IRUSR | S_IWUSR);
  
+ 	/*create a .auto for conf file*/
+ 	sprintf(path, "%s/config_dir/postgresql.auto.conf", pg_data);
+ 	autofile = fopen(path, PG_BINARY_W);
+ 	if (autofile == NULL)
+ 	{
+ 		fprintf(stderr, _("%s: could not open file \"%s\" for writing: %s\n"),
+ 				progname, path, strerror(errno));
+ 		exit_nicely();
+ 	}
+ 
+ 	
+ 	if (fclose(autofile))
+ 	{
+ 		fprintf(stderr, _("%s: could not write file \"%s\": %s\n"),
+ 				progname, path, strerror(errno));
+ 		exit_nicely();
+ 	}
+ 
+ 	chmod(path, S_IRUSR | S_IWUSR);
+ 
+ 
  	free(conflines);
  
  
***************
*** 2823,2828 **** check_need_password(const char *authmethodlocal, const char *authmethodhost)
--- 2853,2934 ----
  	}
  }
  
+ /*
+  * If the given pathname isn't already absolute, make it so, interpreting
+  * it relative to the current working directory.
+  *
+  * Also canonicalizes the path.  The result is always a malloc'd copy.
+  *
+  */
+ static char *
+ make_absolute_path(const char *path)
+ {
+ 	char	   *new;
+ 
+ 	/* Returning null for null input is convenient for some callers */
+ 	if (path == NULL)
+ 		return NULL;
+ 
+ 	if (!is_absolute_path(path))
+ 	{
+ 		char	   *buf;
+ 		size_t		buflen;
+ 
+ 		buflen = MAXPGPATH;
+ 		for (;;)
+ 		{
+ 			buf = malloc(buflen);
+ 			if (!buf)
+ 			{
+ 				fprintf(stderr, _("%s: Memory allocation failed\n"),
+ 				progname);
+ 				exit_nicely();
+ 			}
+ 
+ 			if (getcwd(buf, buflen))
+ 				break;
+ 			else if (errno == ERANGE)
+ 			{
+ 				free(buf);
+ 				buflen *= 2;
+ 				continue;
+ 			}
+ 			else
+ 			{
+ 				free(buf);
+ 				fprintf(stderr, _("%s: could not get current working directory\n"),
+ 				progname);
+ 				exit_nicely();
+ 			}
+ 		}
+ 
+ 		new = malloc(strlen(buf) + strlen(path) + 2);
+ 		if (!new)
+ 		{
+ 			fprintf(stderr, _("%s: Memory allocation failed\n"),
+ 			progname);
+ 			exit_nicely();
+ 		}
+ 		sprintf(new, "%s/%s", buf, path);
+ 		free(buf);
+ 	}
+ 	else
+ 	{
+ 		new = strdup(path);
+ 		if (!new)
+ 		{
+ 			fprintf(stderr, _("%s: Memory allocation failed\n"),
+ 			progname);
+ 			exit_nicely();
+ 		}
+ 	}
+ 
+ 	/* Make sure punctuation is canonical, too */
+ 	canonicalize_path(new);
+ 
+ 	return new;
+ }
+ 
  int
  main(int argc, char *argv[])
  {
***************
*** 2887,2893 **** main(int argc, char *argv[])
  		"base",
  		"base/1",
  		"pg_tblspc",
! 		"pg_stat_tmp"
  	};
  
  	progname = get_progname(argv[0]);
--- 2993,3000 ----
  		"base",
  		"base/1",
  		"pg_tblspc",
! 		"pg_stat_tmp",
! 		"config_dir"
  	};
  
  	progname = get_progname(argv[0]);
*** a/src/include/access/xlog_internal.h
--- b/src/include/access/xlog_internal.h
***************
*** 255,260 **** extern void XLogArchiveCleanup(const char *xlog);
--- 255,261 ----
  /*
   * These aren't in xlog.h because I'd rather not include fmgr.h there.
   */
+ 
  extern Datum pg_start_backup(PG_FUNCTION_ARGS);
  extern Datum pg_stop_backup(PG_FUNCTION_ARGS);
  extern Datum pg_switch_xlog(PG_FUNCTION_ARGS);
*** a/src/include/catalog/pg_proc.h
--- b/src/include/catalog/pg_proc.h
***************
*** 3005,3010 **** DATA(insert OID = 2625 ( pg_ls_dir			PGNSP PGUID 12 1 1000 0 0 f f f f t t v 1 0
--- 3005,3012 ----
  DESCR("list all files in a directory");
  DATA(insert OID = 2626 ( pg_sleep			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "701" _null_ _null_ _null_ _null_ pg_sleep _null_ _null_ _null_ ));
  DESCR("sleep for the specified time in seconds");
+ DATA(insert OID = 2634 ( pg_change_conf     PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 16 "2275 2275" _null_ _null_ _null_ _null_ pg_change_conf _null_ _null_ _null_ ));
+ DESCR("changes a parameter in .auto.conf file");
  
  DATA(insert OID = 2971 (  text				PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 25 "16" _null_ _null_ _null_ _null_ booltext _null_ _null_ _null_ ));
  DESCR("convert boolean to text");
*** a/src/include/commands/dbcommands.h
--- b/src/include/commands/dbcommands.h
***************
*** 58,63 **** extern void RenameDatabase(const char *oldname, const char *newname);
--- 58,64 ----
  extern void AlterDatabase(AlterDatabaseStmt *stmt, bool isTopLevel);
  extern void AlterDatabaseSet(AlterDatabaseSetStmt *stmt);
  extern void AlterDatabaseOwner(const char *dbname, Oid newOwnerId);
+ extern void set_config_file(VariableSetStmt *setstmt);
  
  extern Oid	get_database_oid(const char *dbname, bool missingok);
  extern char *get_database_name(Oid dbid);
*** a/src/include/nodes/parsenodes.h
--- b/src/include/nodes/parsenodes.h
***************
*** 2361,2366 **** typedef struct AlterDatabaseSetStmt
--- 2361,2368 ----
  	VariableSetStmt *setstmt;	/* SET or RESET subcommand */
  } AlterDatabaseSetStmt;
  
+ 
+ 
  /* ----------------------
   *		Dropdb Statement
   * ----------------------
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
***************
*** 482,487 **** extern Datum pg_sleep(PG_FUNCTION_ARGS);
--- 482,488 ----
  extern Datum pg_get_keywords(PG_FUNCTION_ARGS);
  extern Datum pg_typeof(PG_FUNCTION_ARGS);
  extern Datum pg_collation_for(PG_FUNCTION_ARGS);
+ extern Datum pg_change_conf(PG_FUNCTION_ARGS);
  
  /* oid.c */
  extern Datum oidin(PG_FUNCTION_ARGS);
*** a/src/include/utils/guc.h
--- b/src/include/utils/guc.h
***************
*** 191,196 **** typedef enum
--- 191,201 ----
  
  #define GUC_NOT_WHILE_SEC_REST	0x8000	/* can't set if security restricted */
  
+ /*postgresql.auto.file name and its lock*/
+ #define AutoConfigFileName "config_dir/postgresql.auto.conf"
+ #define CONF_LOCK_POSTFIX  ".lock"
+ 
+ 
  /* GUC vars that are actually declared in guc.c, rather than elsewhere */
  extern bool log_duration;
  extern bool Debug_print_plan;
***************
*** 329,334 **** extern void SetPGVariable(const char *name, List *args, bool is_local);
--- 334,343 ----
  extern void GetPGVariable(const char *name, DestReceiver *dest);
  extern TupleDesc GetPGVariableResultDesc(const char *name);
  
+ extern bool
+ ParseAutoConfigFp(FILE *fp, const char *config_file, char * name, int *line_no, int depth, int elevel,
+ 			  			bool *hasmatch);
+ 
  extern void ExecSetVariableStmt(VariableSetStmt *stmt);
  extern char *ExtractSetVariableArgs(VariableSetStmt *stmt);
  
*** a/src/include/utils/guc_tables.h
--- b/src/include/utils/guc_tables.h
***************
*** 260,265 **** extern void build_guc_variables(void);
--- 260,267 ----
  extern const char *config_enum_lookup_by_value(struct config_enum * record, int val);
  extern bool config_enum_lookup_by_name(struct config_enum * record,
  						   const char *value, int *retval);
+ extern struct config_generic *
+ validate_conf_option(const char *name, const char *value);
  
  
  #endif   /* GUC_TABLES_H */

*** a/src/backend/access/transam/xact.c
--- b/src/backend/access/transam/xact.c
***************
*** 1844,1849 **** CommitTransaction(void)
--- 1844,1851 ----
  	/* close large objects before lower-level cleanup */
  	AtEOXact_LargeObject(true);
  
+ 	AtEOXact_UpdateAutoConfFiles(true);
+ 
  	/*
  	 * Mark serializable transaction as complete for predicate locking
  	 * purposes.  This should be done as late as we can put it and still allow
***************
*** 2302,2307 **** AbortTransaction(void)
--- 2304,2310 ----
  	AtAbort_Portals();
  	AtEOXact_LargeObject(false);
  	AtAbort_Notify();
+ 	AtEOXact_UpdateAutoConfFiles(false);
  	AtEOXact_RelationMap(false);
  
  	/*
*** a/src/backend/commands/dbcommands.c
--- b/src/backend/commands/dbcommands.c
***************
*** 58,65 ****
--- 58,74 ----
  #include "utils/snapmgr.h"
  #include "utils/syscache.h"
  #include "utils/tqual.h"
+ #include "utils/guc_tables.h"
+ #include "utils/memutils.h"
  
  
+ /* lock file used in edit postgresql.auto.conf */
+ struct lock_file
+ {
+ 	int			fd;
+ 	char		filename[MAXPGPATH];
+ };
+ 
  typedef struct
  {
  	Oid			src_dboid;		/* source (template) DB */
***************
*** 72,77 **** typedef struct
--- 81,88 ----
  	Oid			dest_tsoid;		/* tablespace we are trying to move to */
  } movedb_failure_params;
  
+ static struct lock_file *lockConfFile = NULL;
+ 
  /* non-export function prototypes */
  static void createdb_failure_callback(int code, Datum arg);
  static void movedb(const char *dbname, const char *tblspcname);
***************
*** 86,91 **** static void remove_dbtablespaces(Oid db_id);
--- 97,108 ----
  static bool check_db_file_conflict(Oid db_id);
  static int	errdetail_busy_db(int notherbackends, int npreparedxacts);
  
+ static int	commit_lock_file(struct lock_file * lk);
+ static void	rollback_lock_file(struct lock_file * lk);
+ static int	close_lock_file(struct lock_file * lk);
+ static void writeAutoConffile(int fd, ConfigVariable **head_p, char *config_file);
+ static void replace_autoline(ConfigVariable **head_p, ConfigVariable **tail_p,
+ 			char *config_file, char *name, char *value, bool value_is_string);
  
  /*
   * CREATE DATABASE
***************
*** 1434,1439 **** AlterDatabaseSet(AlterDatabaseSetStmt *stmt)
--- 1451,1778 ----
  
  
  /*
+  * create a postgres.auto.conf.lock file for postgres.auto.conf 
+  * file so that it act as an lock to prevent concurrent edit on
+  * postgres.auto.conf file
+  */
+ static int
+ lock_confile(struct lock_file * lk, const char *path, int flags)
+ {
+ 	int			ntries = 0;
+ 
+ 	strcpy(lk->filename, path);
+ 	strcat(lk->filename, CONF_LOCK_POSTFIX);
+ 
+ tryAgain:
+ 	lk->fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0600);
+ 	if (0 > lk->fd)
+ 	{
+ 		/*
+ 		 * Couldn't create the lock file. Probably it already exists. If so
+ 		 * wait for some time
+ 		 */
+ 		ntries++;
+ 		if ((errno != EEXIST && errno != EACCES) || ntries > 100)
+ 		{
+ 			if (errno != EEXIST)
+ 			{
+ 				ereport(LOG,
+ 						(errcode_for_file_access(),
+ 						 errmsg("could not create lock file \"%s\": %m",
+ 								lk->filename)));
+ 			}
+ 			else
+ 			{
+ 				ereport(LOG,
+ 						(errcode_for_file_access(),
+ 						 errmsg("could not create lock file \"%s\": %m ", lk->filename),
+ 						 errhint("May be too many concurrent edit into file happening, please wait!! and retry"
+ 								 "or .lock is file accidently left there please clean the file from config_dir")));
+ 			}
+ 
+ 			lk->filename[0] = 0;
+ 		}
+ 		else
+ 		{
+ 			pg_usleep(100000);	/* in total wait for 10sec */
+ 			goto tryAgain;
+ 		}
+ 	}
+ 
+ 	return lk->fd;
+ }
+ 
+ /* function to close the postgres.auto.conf.lock file */
+ int
+ close_lock_file(struct lock_file * lk)
+ {
+ 	int			fd = lk->fd;
+ 
+ 	lk->fd = -1;
+ 	return close(fd);
+ }
+ 
+ 
+ /*
+  * On commit, rename postgres.auto.conf.lock to postgres.auto.conf
+  * As postgres.auto.conf.lock contains updated parameter values.
+  */
+ int
+ commit_lock_file(struct lock_file * lk)
+ {
+ 	char		result_file[MAXPGPATH];
+ 	size_t		i;
+ 
+ 	if (lk->fd >= 0 && close_lock_file(lk))
+ 		return -1;
+ 	strcpy(result_file, lk->filename);
+ 	i = strlen(result_file) - 5;	/* remove .lock charecters */
+ 	result_file[i] = 0;
+ 	if (rename(lk->filename, result_file))
+ 		return -1;
+ 	lk->filename[0] = 0;
+ 	return 0;
+ }
+ 
+ 
+ /*
+  * On rollback, Delete the postgres.auto.conf.lock file, As we did not
+  * modifed anything in postgres.auto.conf
+  */
+ void
+ rollback_lock_file(struct lock_file * lk)
+ {
+ 	if (lk->filename[0])
+ 	{
+ 		if (lk->fd >= 0)
+ 		{
+ 			/* cloase the file */
+ 			close(lk->fd);
+ 		}
+ 
+ 		/* now remove the file */
+ 		unlink(lk->filename);
+ 	}
+ 
+ 	lk->filename[0] = 0;
+ }
+ 
+ 
+ /* Write updated configuration parameter values into postgres.auto.conf.lock */
+ static void
+ writeAutoConffile(int fd, ConfigVariable **head_p, char *config_file)
+ {
+ 	ConfigVariable *item;
+ 	StringInfoData buf;
+ 
+ 	initStringInfo(&buf);
+ 
+ 	for (item = *head_p; item != NULL; item = item->next)
+ 	{
+ 		appendStringInfoString(&buf, item->name);
+ 		appendStringInfoString(&buf, " = ");
+ 
+ 		if (true == item->value_is_string)
+ 		{
+ 			appendStringInfoString(&buf, "\'");
+ 			appendStringInfoString(&buf, item->value);
+ 			appendStringInfoString(&buf, "\'");
+ 		}
+ 		else
+ 		{
+ 			appendStringInfoString(&buf, item->value);
+ 		}
+ 
+ 		appendStringInfoString(&buf, "\n");
+ 
+ 		if (write(fd, buf.data, buf.len) < 0)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("failed to write into to \"postgresql.auto.conf.lock\" file")));
+ 		}
+ 
+ 		resetStringInfo(&buf);
+ 	}
+ 
+ 	pfree(buf.data);
+ 	return;
+ }
+ 
+ 
+ /*
+  * Replace the updated configuration parameter value in postgres.auto.conf
+  * file lines. If it is new then append extra line at the end of lines.
+  */
+ static void
+ replace_autoline(ConfigVariable **head_p, ConfigVariable **tail_p,
+ 					char *config_file, char *name, char *value,
+ 					bool value_is_string)
+ {
+ 
+ 	ConfigVariable *item;
+ 
+ 	if (NULL != *head_p)
+ 	{
+ 		for (item = *head_p; item != NULL; item = item->next)
+ 		{
+ 			if (strcmp(item->name, name) == 0)
+ 			{
+ 				pfree(item->value);
+ 				item->value = pstrdup(value);
+ 				return;
+ 			}
+ 		}
+ 	}
+ 
+ 	item = palloc(sizeof *item);
+ 	item->name = pstrdup(name);
+ 	item->value = pstrdup(value);
+ 	item->value_is_string = value_is_string;
+ 	item->filename = pstrdup(config_file);
+ 	item->next = NULL;
+ 
+ 	if (*head_p == NULL)
+ 	{
+ 		item->sourceline = 1;
+ 		*head_p = item;
+ 	}
+ 	else
+ 	{
+ 		item->sourceline = (*tail_p)->sourceline+1;
+ 		(*tail_p)->next = item;
+ 	}
+ 
+ 	*tail_p = item;
+ 
+ 	return;
+ }
+ 
+ 
+ /*
+  * Edit postgres.conf parameters WITH SQL commands "SET PERSISTENT"
+  * by adding new postgres.auto.conf file in include configuration directory
+  * which will be processed at the end of postgres.conf file
+  */
+ void
+ set_config_file(VariableSetStmt *setstmt)
+ {
+ 	char	   *name;
+ 	char	   *value;
+ 	int			fd = -1;
+ 	FILE	   *infile;
+ 	struct config_generic *record;
+ 	char		abs_path[MAXPGPATH];
+ 	ConfigVariable *head_p = NULL;
+ 	ConfigVariable *tail_p = NULL;
+ 
+ 	/*
+ 	 * This command is modifing the configuration file so no need of
+ 	 * transaction properties, so not allowed inside a transaction.
+ 	 */
+ 	if (IsTransactionBlock())
+ 	{
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_ACTIVE_SQL_TRANSACTION),
+ 				 errmsg("SET PERSISTENT command is not allowed inside a transaction")));
+ 	}
+ 
+ 	if (!superuser())
+ 	{
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+ 				 (errmsg("must be superuser to execute SET PERSISTENT command"))));
+ 	}
+ 
+ 	/*
+ 	 * Validate the name and arguments [value1, value2 ... ].
+ 	 */
+ 
+ 	name = pstrdup(setstmt->name);
+ 	value = ExtractSetVariableArgs(setstmt);
+ 
+ 	record = validate_conf_option(name, value);
+ 	if (!record)
+ 		ereport(ERROR,
+ 				(errmsg("invalid value for parameter \"%s\": \"%s\"", name, value)));
+ 
+ 	/* Create the postgres.auto.conf.lock file */
+ 	join_path_components(abs_path, data_directory, AutoConfigFileName);
+ 	canonicalize_path(abs_path);
+ 
+ 	lockConfFile = MemoryContextAllocZero(TopTransactionContext, sizeof(struct lock_file));
+ 
+ 	fd = lock_confile(lockConfFile, abs_path, 0);
+ 	if (fd < 0)
+ 	{
+ 		pfree(lockConfFile);
+ 		lockConfFile = NULL;
+ 		ereport(ERROR,
+ 				(errmsg("\"postgresql.auto.conf.lock\" file creation failed")));
+ 	}
+ 
+ 	/* open postgres.auto.conf file */
+ 	infile = AllocateFile(abs_path, "r");
+ 	if (infile == NULL)
+ 	{
+ 		ereport(ERROR,
+ 				(errmsg("failed to open \"postgresql.auto.conf\" file")));
+ 	}
+ 
+ 	/* Parse the postgres.auto.conf file */
+ 	ParseConfigFp(infile, abs_path, -1, LOG, &head_p, &tail_p);
+ 
+ 	FreeFile(infile);
+ 
+ 	/* replace with new value */
+ 	replace_autoline(&head_p, &tail_p, abs_path, name, value,
+ 					  (record->vartype == PGC_STRING) ? true : false);
+ 
+ 	/* Write the New contents to postgres.auto.conf.lock file */
+ 	writeAutoConffile(fd, &head_p, abs_path);
+ 
+ 	/*
+ 	 * On Commit, rename postgres.auto.conf.lock to postgres.auto.conf
+ 	 * and On Rollback, delete the postgres.auto.conf.lock
+ 	 */
+ 
+ 	return;
+ }
+ 
+ /*
+  * This routine is called during transaction commit or abort.
+  *
+  * On commit, renames the .auto.conf.lock to .auto.conf, for updateding changes
+  * into .auto.conf file
+  *
+  * On abort, just delete the .auto.conf.lock file.
+  *
+  * NB: this should be the last step before actual transaction commit.
+  * If any error aborts the transaction after we run this code, the postmaster
+  * will still have received and cached the changed data; so minimize the
+  * window for such problems.
+  */
+ void
+ AtEOXact_UpdateAutoConfFiles(bool isCommit)
+ {
+ 	if (lockConfFile)
+ 	{
+ 		if (isCommit)
+ 		{
+ 			if (commit_lock_file(lockConfFile) < 0)
+ 				ereport(ERROR,
+ 				(errmsg("commiting chages to \"postgresql.auto.conf\" failed")));
+ 		}
+ 		else
+ 		{
+ 			rollback_lock_file(lockConfFile);
+ 		}
+ 
+ 		pfree(lockConfFile);
+ 		lockConfFile = NULL;
+ 	}
+ }
+ 
+ /*
   * ALTER DATABASE name OWNER TO newowner
   */
  void
*** a/src/backend/parser/gram.y
--- b/src/backend/parser/gram.y
***************
*** 564,571 **** static void processCASbits(int cas_bits, int location, const char *constrType,
  	OBJECT_P OF OFF OFFSET OIDS ON ONLY OPERATOR OPTION OPTIONS OR
  	ORDER OUT_P OUTER_P OVER OVERLAPS OVERLAY OWNED OWNER
  
! 	PARSER PARTIAL PARTITION PASSING PASSWORD PLACING PLANS POSITION
! 	PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY
  	PRIOR PRIVILEGES PROCEDURAL PROCEDURE
  
  	QUOTE
--- 564,571 ----
  	OBJECT_P OF OFF OFFSET OIDS ON ONLY OPERATOR OPTION OPTIONS OR
  	ORDER OUT_P OUTER_P OVER OVERLAPS OVERLAY OWNED OWNER
  
! 	PARSER PARTIAL PARTITION PASSING PASSWORD PERSISTENT PLACING PLANS
! 	POSITION PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY
  	PRIOR PRIVILEGES PROCEDURAL PROCEDURE
  
  	QUOTE
***************
*** 1293,1298 **** VariableSetStmt:
--- 1293,1307 ----
  					n->is_local = false;
  					$$ = (Node *) n;
  				}
+ 			| SET PERSISTENT var_name '=' var_list
+ 				{
+ 					VariableSetStmt *n = makeNode(VariableSetStmt);
+ 					n->kind = VAR_SET_VALUE;
+ 					n->name = $3;
+ 					n->args = $5;
+ 					n->is_persistent = true;
+ 					$$ = (Node *)n;
+ 				}
  		;
  
  set_rest:
***************
*** 12586,12591 **** unreserved_keyword:
--- 12595,12601 ----
  			| PARTITION
  			| PASSING
  			| PASSWORD
+ 			| PERSISTENT
  			| PLANS
  			| PRECEDING
  			| PREPARE
*** a/src/backend/postmaster/postmaster.c
--- b/src/backend/postmaster/postmaster.c
***************
*** 507,512 **** PostmasterMain(int argc, char *argv[])
--- 507,513 ----
  	char	   *userDoption = NULL;
  	bool		listen_addr_saved = false;
  	int			i;
+ 	char		conf_lock_file[MAXPGPATH];
  
  	MyProcPid = PostmasterPid = getpid();
  
***************
*** 1163,1168 **** PostmasterMain(int argc, char *argv[])
--- 1164,1174 ----
  	 */
  	RemovePgTempFiles();
  
+ 	/* Remove postgres.auto.conf.lock file make be left over from last crash */
+ 	strcpy(conf_lock_file, AutoConfigFileName);
+ 	strcat(conf_lock_file, CONF_LOCK_POSTFIX);
+ 	unlink(conf_lock_file);
+ 
  	/*
  	 * Remember postmaster startup time
  	 */
*** a/src/backend/replication/basebackup.c
--- b/src/backend/replication/basebackup.c
***************
*** 581,586 **** sendDir(char *path, int basepathlen, bool sizeonly)
--- 581,592 ----
  					strlen(PG_TEMP_FILE_PREFIX)) == 0)
  			continue;
  
+ 		/* skip lock files used in postgresql.auto.conf edit */
+ 		if (strncmp(de->d_name,
+ 					"postgresql.auto.conf.lock",
+ 					strlen("postgresql.auto.conf.lock")) == 0)
+ 			continue;
+ 
  		/*
  		 * If there's a backup_label file, it belongs to a backup started by
  		 * the user with pg_start_backup(). It is *not* correct for this
*** a/src/backend/tcop/utility.c
--- b/src/backend/tcop/utility.c
***************
*** 1145,1151 **** standard_ProcessUtility(Node *parsetree,
  			break;
  
  		case T_VariableSetStmt:
! 			ExecSetVariableStmt((VariableSetStmt *) parsetree);
  			break;
  
  		case T_VariableShowStmt:
--- 1145,1158 ----
  			break;
  
  		case T_VariableSetStmt:
! 			if (((VariableSetStmt *) parsetree)->is_persistent == true)
! 			{
! 				set_config_file((VariableSetStmt *) parsetree);
! 			}
! 			else
! 			{
! 				ExecSetVariableStmt((VariableSetStmt *) parsetree);
! 			}
  			break;
  
  		case T_VariableShowStmt:
*** a/src/backend/utils/misc/guc-file.l
--- b/src/backend/utils/misc/guc-file.l
***************
*** 533,538 **** ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
--- 533,539 ----
  	{
  		char	   *opt_name = NULL;
  		char	   *opt_value = NULL;
+ 		bool		is_string = false;
  		ConfigVariable *item;
  
  		if (token == GUC_EOL)	/* empty or comment line */
***************
*** 556,562 **** ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
--- 557,566 ----
  			token != GUC_UNQUOTED_STRING)
  			goto parse_error;
  		if (token == GUC_STRING)	/* strip quotes and escapes */
+ 		{
  			opt_value = GUC_scanstr(yytext);
+ 			is_string = true;
+ 		}
  		else
  			opt_value = pstrdup(yytext);
  
***************
*** 620,625 **** ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
--- 624,630 ----
  			item = palloc(sizeof *item);
  			item->name = opt_name;
  			item->value = opt_value;
+ 			item->value_is_string = is_string;
  			item->filename = pstrdup(config_file);
  			item->sourceline = ConfigFileLineno-1;
  			item->next = NULL;
*** a/src/backend/utils/misc/guc.c
--- b/src/backend/utils/misc/guc.c
***************
*** 5105,5110 **** config_enum_get_options(struct config_enum * record, const char *prefix,
--- 5105,5260 ----
  	return retstr.data;
  }
  
+ /*given key and value validate the config value*/
+ 
+ struct config_generic *
+ validate_conf_option(const char *name, const char *value)
+ {
+ 	struct config_generic *record;
+ 
+ 	record = find_option(name, true, LOG);
+ 	if (record == NULL)
+ 	{
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_UNDEFINED_OBJECT),
+ 			   errmsg("unrecognized configuration parameter \"%s\"", name)));
+ 	}
+ 
+ 	if (record->context == PGC_INTERNAL)
+ 	{
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
+ 				 errmsg("parameter \"%s\" cannot be changed",
+ 						name)));
+ 	}
+ 
+ 	/*
+ 	 * Evaluate value and set variable.
+ 	 */
+ 	switch (record->vartype)
+ 	{
+ 
+ 		case PGC_BOOL:
+ 			{
+ 				struct config_bool *conf = (struct config_bool *) record;
+ 				bool		newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					if (!parse_bool(value, &newval))
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						  errmsg("parameter \"%s\" requires a Boolean value",
+ 								 name)));
+ 					}
+ 					if (!call_bool_check_hook(conf, &newval, &newextra,
+ 											  PGC_S_FILE, LOG))
+ 						return NULL;
+ 				}
+ 			}
+ 			break;
+ 
+ 		case PGC_INT:
+ 			{
+ 				struct config_int *conf = (struct config_int *) record;
+ 				int			newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					const char *hintmsg;
+ 
+ 					if (!parse_int(value, &newval, conf->gen.flags, &hintmsg))
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						 errmsg("invalid value for parameter \"%s\": \"%s\"",
+ 								name, value),
+ 								 hintmsg ? errhint("%s", _(hintmsg)) : 0));
+ 					}
+ 					if (newval < conf->min || newval > conf->max)
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 								 errmsg("%d is outside the valid range for parameter \"%s\" (%d .. %d)",
+ 										newval, name, conf->min, conf->max)));
+ 					}
+ 					if (!call_int_check_hook(conf, &newval, &newextra,
+ 											 PGC_S_FILE, LOG))
+ 						return NULL;
+ 				}
+ 			}
+ 
+ 			break;
+ 
+ 		case PGC_REAL:
+ 			{
+ 				struct config_real *conf = (struct config_real *) record;
+ 				double		newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					if (!parse_real(value, &newval))
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						  errmsg("parameter \"%s\" requires a numeric value",
+ 								 name)));
+ 					}
+ 					if (newval < conf->min || newval > conf->max)
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 								 errmsg("%g is outside the valid range for parameter \"%s\" (%g .. %g)",
+ 										newval, name, conf->min, conf->max)));
+ 					}
+ 					if (!call_real_check_hook(conf, &newval, &newextra,
+ 											  PGC_S_FILE, LOG))
+ 						return NULL;
+ 				}
+ 			}
+ 
+ 			break;
+ 
+ 		case PGC_STRING:
+ 			{
+ 				struct config_string *conf = (struct config_string *) record;
+ 				char	   *newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					/*
+ 					 * The value passed by the caller could be transient, so
+ 					 * we always strdup it.
+ 					 */
+ 					newval = guc_strdup(LOG, value);
+ 					if (newval == NULL)
+ 						return NULL;
+ 
+ 					/*
+ 					 * The only built-in "parsing" check we have is to apply
+ 					 * truncation if GUC_IS_NAME.
+ 					 */
+ 					if (conf->gen.flags & GUC_IS_NAME)
+ 						truncate_identifier(newval, strlen(newval), true);
+ 
+ 					if (!call_string_check_hook(conf, &newval, &newextra,
+ 												PGC_S_FILE, LOG))
+ 					{
+ 						free(newval);
+ 						return NULL;
+ 					}
+ 				}
+ 			}
+ 	}
+ 
+ 	return record;
+ }
+ 
  
  /*
   * Sets option `name' to given value.
*** a/src/bin/initdb/initdb.c
--- b/src/bin/initdb/initdb.c
***************
*** 177,182 **** static const char *backend_options = "--single -F -O -c search_path=pg_catalog -
--- 177,183 ----
  static char bin_path[MAXPGPATH];
  static char backend_exec[MAXPGPATH];
  
+ char	   *make_absolute_path(const char *path);
  static void *pg_malloc(size_t size);
  static char *pg_strdup(const char *s);
  static char **replace_token(char **lines,
***************
*** 1163,1168 **** setup_config(void)
--- 1164,1171 ----
  	char		repltok[MAXPGPATH];
  	char		path[MAXPGPATH];
  	const char *default_timezone;
+ 	char	   *abs_data_dir;
+ 	FILE	   *autofile;
  
  	fputs(_("creating configuration files ... "), stdout);
  	fflush(stdout);
***************
*** 1245,1255 **** setup_config(void)
--- 1248,1284 ----
  		conflines = replace_token(conflines, "#log_timezone = 'GMT'", repltok);
  	}
  
+ 	abs_data_dir = make_absolute_path(pg_data);
+ 
+ 	snprintf(repltok, sizeof(repltok), "include_dir = '%s/config_dir'",
+ 			 abs_data_dir);
+ 	conflines = replace_token(conflines, "#include_dir = 'conf.d'", repltok);
+ 
  	snprintf(path, sizeof(path), "%s/postgresql.conf", pg_data);
  
  	writefile(path, conflines);
  	chmod(path, S_IRUSR | S_IWUSR);
  
+ 	/* create a .auto for conf file */
+ 	sprintf(path, "%s/config_dir/postgresql.auto.conf", pg_data);
+ 	autofile = fopen(path, PG_BINARY_W);
+ 	if (autofile == NULL)
+ 	{
+ 		fprintf(stderr, _("%s: could not open file \"%s\" for writing: %s\n"),
+ 				progname, path, strerror(errno));
+ 		exit_nicely();
+ 	}
+ 
+ 	if (fclose(autofile))
+ 	{
+ 		fprintf(stderr, _("%s: could not write file \"%s\": %s\n"),
+ 				progname, path, strerror(errno));
+ 		exit_nicely();
+ 	}
+ 
+ 	chmod(path, S_IRUSR | S_IWUSR);
+ 
+ 
  	free(conflines);
  
  
***************
*** 2823,2828 **** check_need_password(const char *authmethodlocal, const char *authmethodhost)
--- 2852,2933 ----
  	}
  }
  
+ /*
+  * If the given pathname isn't already absolute, make it so, interpreting
+  * it relative to the current working directory.
+  *
+  * Also canonicalizes the path.  The result is always a malloc'd copy.
+  *
+  */
+ char *
+ make_absolute_path(const char *path)
+ {
+ 	char	   *new;
+ 
+ 	/* Returning null for null input is convenient for some callers */
+ 	if (path == NULL)
+ 		return NULL;
+ 
+ 	if (!is_absolute_path(path))
+ 	{
+ 		char	   *buf;
+ 		size_t		buflen;
+ 
+ 		buflen = MAXPGPATH;
+ 		for (;;)
+ 		{
+ 			buf = malloc(buflen);
+ 			if (!buf)
+ 			{
+ 				fprintf(stderr, _("%s: Memory allocation failed\n"),
+ 						progname);
+ 				exit_nicely();
+ 			}
+ 
+ 			if (getcwd(buf, buflen))
+ 				break;
+ 			else if (errno == ERANGE)
+ 			{
+ 				free(buf);
+ 				buflen *= 2;
+ 				continue;
+ 			}
+ 			else
+ 			{
+ 				free(buf);
+ 				fprintf(stderr, _("%s: could not get current working directory\n"),
+ 						progname);
+ 				exit_nicely();
+ 			}
+ 		}
+ 
+ 		new = malloc(strlen(buf) + strlen(path) + 2);
+ 		if (!new)
+ 		{
+ 			fprintf(stderr, _("%s: Memory allocation failed\n"),
+ 					progname);
+ 			exit_nicely();
+ 		}
+ 		sprintf(new, "%s/%s", buf, path);
+ 		free(buf);
+ 	}
+ 	else
+ 	{
+ 		new = strdup(path);
+ 		if (!new)
+ 		{
+ 			fprintf(stderr, _("%s: Memory allocation failed\n"),
+ 					progname);
+ 			exit_nicely();
+ 		}
+ 	}
+ 
+ 	/* Make sure punctuation is canonical, too */
+ 	canonicalize_path(new);
+ 
+ 	return new;
+ }
+ 
  int
  main(int argc, char *argv[])
  {
***************
*** 2887,2893 **** main(int argc, char *argv[])
  		"base",
  		"base/1",
  		"pg_tblspc",
! 		"pg_stat_tmp"
  	};
  
  	progname = get_progname(argv[0]);
--- 2992,2999 ----
  		"base",
  		"base/1",
  		"pg_tblspc",
! 		"pg_stat_tmp",
! 		"config_dir"
  	};
  
  	progname = get_progname(argv[0]);
*** a/src/include/commands/dbcommands.h
--- b/src/include/commands/dbcommands.h
***************
*** 58,63 **** extern void RenameDatabase(const char *oldname, const char *newname);
--- 58,64 ----
  extern void AlterDatabase(AlterDatabaseStmt *stmt, bool isTopLevel);
  extern void AlterDatabaseSet(AlterDatabaseSetStmt *stmt);
  extern void AlterDatabaseOwner(const char *dbname, Oid newOwnerId);
+ extern void set_config_file(VariableSetStmt *setstmt);
  
  extern Oid	get_database_oid(const char *dbname, bool missingok);
  extern char *get_database_name(Oid dbid);
***************
*** 67,70 **** extern void dbase_desc(StringInfo buf, uint8 xl_info, char *rec);
--- 68,73 ----
  
  extern void check_encoding_locale_matches(int encoding, const char *collate, const char *ctype);
  
+ extern void AtEOXact_UpdateAutoConfFiles(bool isCommit);
+ 
  #endif   /* DBCOMMANDS_H */
*** a/src/include/nodes/parsenodes.h
--- b/src/include/nodes/parsenodes.h
***************
*** 1425,1430 **** typedef struct VariableSetStmt
--- 1425,1431 ----
  	char	   *name;			/* variable to be set */
  	List	   *args;			/* List of A_Const nodes */
  	bool		is_local;		/* SET LOCAL? */
+ 	bool		is_persistent;		/* SET PERSISTENT? */	
  } VariableSetStmt;
  
  /* ----------------------
*** a/src/include/parser/kwlist.h
--- b/src/include/parser/kwlist.h
***************
*** 279,284 **** PG_KEYWORD("partial", PARTIAL, UNRESERVED_KEYWORD)
--- 279,285 ----
  PG_KEYWORD("partition", PARTITION, UNRESERVED_KEYWORD)
  PG_KEYWORD("passing", PASSING, UNRESERVED_KEYWORD)
  PG_KEYWORD("password", PASSWORD, UNRESERVED_KEYWORD)
+ PG_KEYWORD("persistent", PERSISTENT, UNRESERVED_KEYWORD)
  PG_KEYWORD("placing", PLACING, RESERVED_KEYWORD)
  PG_KEYWORD("plans", PLANS, UNRESERVED_KEYWORD)
  PG_KEYWORD("position", POSITION, COL_NAME_KEYWORD)
*** a/src/include/utils/guc.h
--- b/src/include/utils/guc.h
***************
*** 105,110 **** typedef struct ConfigVariable
--- 105,111 ----
  {
  	char	   *name;
  	char	   *value;
+ 	int			value_is_string;
  	char	   *filename;
  	int			sourceline;
  	struct ConfigVariable *next;
***************
*** 191,196 **** typedef enum
--- 192,201 ----
  
  #define GUC_NOT_WHILE_SEC_REST	0x8000	/* can't set if security restricted */
  
+ /* postgresql.auto.file name and its lock */
+ #define AutoConfigFileName "config_dir/postgresql.auto.conf"
+ #define CONF_LOCK_POSTFIX  ".lock"
+ 
  /* GUC vars that are actually declared in guc.c, rather than elsewhere */
  extern bool log_duration;
  extern bool Debug_print_plan;
*** a/src/include/utils/guc_tables.h
--- b/src/include/utils/guc_tables.h
***************
*** 260,265 **** extern void build_guc_variables(void);
--- 260,267 ----
  extern const char *config_enum_lookup_by_value(struct config_enum * record, int val);
  extern bool config_enum_lookup_by_name(struct config_enum * record,
  						   const char *value, int *retval);
+ extern struct config_generic * validate_conf_option(const char *name,
+ 								const char *value);
  
  
  #endif   /* GUC_TABLES_H */

*** a/doc/src/sgml/ref/reset.sgml
--- b/doc/src/sgml/ref/reset.sgml
***************
*** 21,28 **** PostgreSQL documentation
  
   <refsynopsisdiv>
  <synopsis>
! RESET <replaceable class="PARAMETER">configuration_parameter</replaceable>
! RESET ALL
  </synopsis>
   </refsynopsisdiv>
  
--- 21,28 ----
  
   <refsynopsisdiv>
  <synopsis>
! RESET [ PERSISTENT ] <replaceable class="PARAMETER">configuration_parameter</replaceable>
! RESET [ PERSISTENT ] ALL
  </synopsis>
   </refsynopsisdiv>
  
***************
*** 36,41 **** RESET ALL
--- 36,43 ----
  <synopsis>
  SET <replaceable class="parameter">configuration_parameter</replaceable> TO DEFAULT
  </synopsis>
+    <command>RESET PERSISTENT</command> deletes the entry in the <filename>postgresql.auto.conf</filename>.
+    The values will be effective after reload of server configuration (SIGHUP) or server startup.
     Refer to <xref linkend="sql-set"> for
     details.
    </para>
***************
*** 82,87 **** SET <replaceable class="parameter">configuration_parameter</replaceable> TO DEFA
--- 84,100 ----
      </listitem>
     </varlistentry>
    </variablelist>
+     
+   <varlistentry>
+     <term><literal>PERSISTENT</></term>
+     <listitem>
+      <para>
+       Deletes the configuration paramters in <filename>postgresql.auto.conf</filename>.
+       These configuration parameters takes effect after reload of configuration
+       file (SIGHUP) or in next server start based on type of configuration parameter modified.
+      </para>
+     </listitem>
+    </varlistentry>
   </refsect1>
  
   <refsect1>
*** a/doc/src/sgml/ref/set.sgml
--- b/doc/src/sgml/ref/set.sgml
***************
*** 21,28 **** PostgreSQL documentation
  
   <refsynopsisdiv>
  <synopsis>
! SET [ SESSION | LOCAL ] <replaceable class="PARAMETER">configuration_parameter</replaceable> { TO | = } { <replaceable class="PARAMETER">value</replaceable> | '<replaceable class="PARAMETER">value</replaceable>' | DEFAULT }
! SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</replaceable> | LOCAL | DEFAULT }
  </synopsis>
   </refsynopsisdiv>
  
--- 21,28 ----
  
   <refsynopsisdiv>
  <synopsis>
! SET [ SESSION | LOCAL | PERSISTENT ] <replaceable class="PARAMETER">configuration_parameter</replaceable> { TO | = } { <replaceable class="PARAMETER">value</replaceable> | '<replaceable class="PARAMETER">value</replaceable>' | DEFAULT }
! SET [ SESSION | LOCAL | PERSISTENT ] TIME ZONE { <replaceable class="PARAMETER">timezone</replaceable> | LOCAL | DEFAULT }
  </synopsis>
   </refsynopsisdiv>
  
***************
*** 50,55 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
--- 50,64 ----
    </para>
  
    <para>
+    The <command>SET PERSISTENT</command> write the configuration parameter values to
+    <filename>postgresql.auto.conf</filename> file. with <literal>DEFAULT</literal> write the 
+    configuration parameter values to default value in <filename>postgresql.auto.conf</filename> file.
+    For deleting configuration entry in <filename>postgresql.auto.conf</filename> file use the 
+    <command>RESET PERSISTENT</command>. The values will be effective after reload of 
+    server configuration (SIGHUP) or server startup.  
+   </para>
+   
+   <para>
     The effects of <command>SET LOCAL</command> last only till the end of
     the current transaction, whether committed or not.  A special case is
     <command>SET</command> followed by <command>SET LOCAL</command> within
***************
*** 86,92 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
      <application>PL/pgSQL</application> exception block.  This behavior
      has been changed because it was deemed unintuitive.
     </para>
!   </note>
   </refsect1>
  
   <refsect1>
--- 95,101 ----
      <application>PL/pgSQL</application> exception block.  This behavior
      has been changed because it was deemed unintuitive.
     </para>
!    </note>
   </refsect1>
  
   <refsect1>
***************
*** 98,105 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
      <listitem>
       <para>
        Specifies that the command takes effect for the current session.
!       (This is the default if neither <literal>SESSION</> nor
!       <literal>LOCAL</> appears.)
       </para>
      </listitem>
     </varlistentry>
--- 107,114 ----
      <listitem>
       <para>
        Specifies that the command takes effect for the current session.
!       (This is the default option, if any of <literal>SESSION</>, 
!       <literal>LOCAL</> or <literal>PERSISTENT</> are not provided.)
       </para>
      </listitem>
     </varlistentry>
***************
*** 119,124 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
--- 128,144 ----
     </varlistentry>
  
     <varlistentry>
+     <term><literal>PERSISTENT</></term>
+     <listitem>
+      <para>
+       Writes updated configuration paramters in <filename>postgresql.auto.conf</filename>.
+       These configuration parameters takes effect after reload of configuration
+       file (SIGHUP) or in next server start based on type of configuration parameter modified.
+      </para>
+     </listitem>
+    </varlistentry>
+ 
+    <varlistentry>
      <term><replaceable class="PARAMETER">configuration_parameter</replaceable></term>
      <listitem>
       <para>
***************
*** 154,160 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
      <varlistentry>
       <term><literal>SCHEMA</literal></term>
       <listitem>
!       <para><literal>SET SCHEMA '<replaceable>value</>'</> is an alias for
         <literal>SET search_path TO <replaceable>value</></>.  Only one
         schema can be specified using this syntax.
        </para>
--- 174,180 ----
      <varlistentry>
       <term><literal>SCHEMA</literal></term>
       <listitem>
!       <para><literal>SET [ PERSISTENT ] SCHEMA '<replaceable>value</>'</> is an alias for
         <literal>SET search_path TO <replaceable>value</></>.  Only one
         schema can be specified using this syntax.
        </para>
***************
*** 164,170 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
      <varlistentry>
       <term><literal>NAMES</literal></term>
       <listitem>
!       <para><literal>SET NAMES <replaceable>value</></> is an alias for
         <literal>SET client_encoding TO <replaceable>value</></>.
        </para>
       </listitem>
--- 184,190 ----
      <varlistentry>
       <term><literal>NAMES</literal></term>
       <listitem>
!       <para><literal>SET [ PERSISTENT ] NAMES <replaceable>value</></> is an alias for
         <literal>SET client_encoding TO <replaceable>value</></>.
        </para>
       </listitem>
***************
*** 192,198 **** SELECT setseed(<replaceable>value</replaceable>);
      <varlistentry>
       <term><literal>TIME ZONE</literal></term>
       <listitem>
!       <para><literal>SET TIME ZONE <replaceable>value</></> is an alias
         for <literal>SET timezone TO <replaceable>value</></>.  The
         syntax <literal>SET TIME ZONE</literal> allows special syntax
         for the time zone specification.  Here are examples of valid
--- 212,218 ----
      <varlistentry>
       <term><literal>TIME ZONE</literal></term>
       <listitem>
!       <para><literal>SET [ PERSISTENT ] TIME ZONE <replaceable>value</></> is an alias
         for <literal>SET timezone TO <replaceable>value</></>.  The
         syntax <literal>SET TIME ZONE</literal> allows special syntax
         for the time zone specification.  Here are examples of valid
*** a/src/backend/nodes/copyfuncs.c
--- b/src/backend/nodes/copyfuncs.c
***************
*** 3264,3269 **** _copyVariableSetStmt(const VariableSetStmt *from)
--- 3264,3270 ----
  	COPY_STRING_FIELD(name);
  	COPY_NODE_FIELD(args);
  	COPY_SCALAR_FIELD(is_local);
+ 	COPY_SCALAR_FIELD(is_persistent);
  
  	return newnode;
  }
*** a/src/backend/nodes/equalfuncs.c
--- b/src/backend/nodes/equalfuncs.c
***************
*** 1555,1560 **** _equalVariableSetStmt(const VariableSetStmt *a, const VariableSetStmt *b)
--- 1555,1561 ----
  	COMPARE_STRING_FIELD(name);
  	COMPARE_NODE_FIELD(args);
  	COMPARE_SCALAR_FIELD(is_local);
+ 	COMPARE_SCALAR_FIELD(is_persistent);
  
  	return true;
  }
*** a/src/backend/parser/gram.y
--- b/src/backend/parser/gram.y
***************
*** 394,400 **** static void processCASbits(int cas_bits, int location, const char *constrType,
  
  %type <istmt>	insert_rest
  
! %type <vsetstmt> set_rest set_rest_more SetResetClause FunctionSetResetClause
  
  %type <node>	TableElement TypedTableElement ConstraintElem TableFuncElement
  				ForeignTableElement
--- 394,401 ----
  
  %type <istmt>	insert_rest
  
! %type <vsetstmt> set_rest set_rest_common set_rest_more reset_common
! 				 SetResetClause FunctionSetResetClause
  
  %type <node>	TableElement TypedTableElement ConstraintElem TableFuncElement
  				ForeignTableElement
***************
*** 564,571 **** static void processCASbits(int cas_bits, int location, const char *constrType,
  	OBJECT_P OF OFF OFFSET OIDS ON ONLY OPERATOR OPTION OPTIONS OR
  	ORDER OUT_P OUTER_P OVER OVERLAPS OVERLAY OWNED OWNER
  
! 	PARSER PARTIAL PARTITION PASSING PASSWORD PLACING PLANS POSITION
! 	PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY
  	PRIOR PRIVILEGES PROCEDURAL PROCEDURE
  
  	QUOTE
--- 565,572 ----
  	OBJECT_P OF OFF OFFSET OIDS ON ONLY OPERATOR OPTION OPTIONS OR
  	ORDER OUT_P OUTER_P OVER OVERLAPS OVERLAY OWNED OWNER
  
! 	PARSER PARTIAL PARTITION PASSING PASSWORD PERSISTENT PLACING PLANS
! 	POSITION PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY
  	PRIOR PRIVILEGES PROCEDURAL PROCEDURE
  
  	QUOTE
***************
*** 1293,1298 **** VariableSetStmt:
--- 1294,1305 ----
  					n->is_local = false;
  					$$ = (Node *) n;
  				}
+ 			| SET PERSISTENT set_rest_common
+ 				{
+ 					VariableSetStmt *n = $3;
+ 					n->is_persistent = true;
+ 					$$ = (Node *) n;
+ 				}
  		;
  
  set_rest:
***************
*** 1315,1321 **** set_rest:
  			| set_rest_more
  			;
  
! set_rest_more:	/* Generic SET syntaxes: */
  			var_name TO var_list
  				{
  					VariableSetStmt *n = makeNode(VariableSetStmt);
--- 1322,1328 ----
  			| set_rest_more
  			;
  
! set_rest_common:	/* common SET syntaxes: */
  			var_name TO var_list
  				{
  					VariableSetStmt *n = makeNode(VariableSetStmt);
***************
*** 1346,1358 **** set_rest_more:	/* Generic SET syntaxes: */
  					n->name = $1;
  					$$ = n;
  				}
- 			| var_name FROM CURRENT_P
- 				{
- 					VariableSetStmt *n = makeNode(VariableSetStmt);
- 					n->kind = VAR_SET_CURRENT;
- 					n->name = $1;
- 					$$ = n;
- 				}
  			/* Special syntaxes mandated by SQL standard: */
  			| TIME ZONE zone_value
  				{
--- 1353,1358 ----
***************
*** 1365,1378 **** set_rest_more:	/* Generic SET syntaxes: */
  						n->kind = VAR_SET_DEFAULT;
  					$$ = n;
  				}
- 			| CATALOG_P Sconst
- 				{
- 					ereport(ERROR,
- 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
- 							 errmsg("current database cannot be changed"),
- 							 parser_errposition(@2)));
- 					$$ = NULL; /*not reached*/
- 				}
  			| SCHEMA Sconst
  				{
  					VariableSetStmt *n = makeNode(VariableSetStmt);
--- 1365,1370 ----
***************
*** 1381,1386 **** set_rest_more:	/* Generic SET syntaxes: */
--- 1373,1405 ----
  					n->args = list_make1(makeStringConst($2, @2));
  					$$ = n;
  				}
+ 			| XML_P OPTION document_or_content
+ 				{
+ 					VariableSetStmt *n = makeNode(VariableSetStmt);
+ 					n->kind = VAR_SET_VALUE;
+ 					n->name = "xmloption";
+ 					n->args = list_make1(makeStringConst($3 == XMLOPTION_DOCUMENT ? "DOCUMENT" : "CONTENT", @3));
+ 					$$ = n;
+ 				}
+ 			;
+ 
+ set_rest_more:	/* Generic SET syntaxes: */
+ 			set_rest_common
+ 			| var_name FROM CURRENT_P
+ 				{
+ 					VariableSetStmt *n = makeNode(VariableSetStmt);
+ 					n->kind = VAR_SET_CURRENT;
+ 					n->name = $1;
+ 					$$ = n;
+ 				}
+ 			| CATALOG_P Sconst
+ 				{
+ 					ereport(ERROR,
+ 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ 							 errmsg("current database cannot be changed"),
+ 							 parser_errposition(@2)));
+ 					$$ = NULL; /*not reached*/
+ 				}
  			| NAMES opt_encoding
  				{
  					VariableSetStmt *n = makeNode(VariableSetStmt);
***************
*** 1415,1428 **** set_rest_more:	/* Generic SET syntaxes: */
  					n->name = "session_authorization";
  					$$ = n;
  				}
- 			| XML_P OPTION document_or_content
- 				{
- 					VariableSetStmt *n = makeNode(VariableSetStmt);
- 					n->kind = VAR_SET_VALUE;
- 					n->name = "xmloption";
- 					n->args = list_make1(makeStringConst($3 == XMLOPTION_DOCUMENT ? "DOCUMENT" : "CONTENT", @3));
- 					$$ = n;
- 				}
  			/* Special syntaxes invented by PostgreSQL: */
  			| TRANSACTION SNAPSHOT Sconst
  				{
--- 1434,1439 ----
***************
*** 1542,1582 **** ColId_or_Sconst:
  		;
  
  VariableResetStmt:
! 			RESET var_name
! 				{
! 					VariableSetStmt *n = makeNode(VariableSetStmt);
! 					n->kind = VAR_RESET;
! 					n->name = $2;
! 					$$ = (Node *) n;
! 				}
! 			| RESET TIME ZONE
! 				{
! 					VariableSetStmt *n = makeNode(VariableSetStmt);
! 					n->kind = VAR_RESET;
! 					n->name = "timezone";
! 					$$ = (Node *) n;
! 				}
! 			| RESET TRANSACTION ISOLATION LEVEL
! 				{
! 					VariableSetStmt *n = makeNode(VariableSetStmt);
! 					n->kind = VAR_RESET;
! 					n->name = "transaction_isolation";
! 					$$ = (Node *) n;
! 				}
! 			| RESET SESSION AUTHORIZATION
! 				{
! 					VariableSetStmt *n = makeNode(VariableSetStmt);
! 					n->kind = VAR_RESET;
! 					n->name = "session_authorization";
! 					$$ = (Node *) n;
! 				}
! 			| RESET ALL
! 				{
! 					VariableSetStmt *n = makeNode(VariableSetStmt);
! 					n->kind = VAR_RESET_ALL;
! 					$$ = (Node *) n;
! 				}
! 		;
  
  /* SetResetClause allows SET or RESET without LOCAL */
  SetResetClause:
--- 1553,1607 ----
  		;
  
  VariableResetStmt:
! 	 RESET PERSISTENT reset_common
! 		{
! 			VariableSetStmt *n = $3;
! 			n->is_persistent=true;
! 			$$ = (Node *) n;
! 		}
! 	| RESET reset_common
! 		{
! 			VariableSetStmt *n = $2;
! 			$$ = (Node *) n;
! 		}
! 	| RESET TRANSACTION ISOLATION LEVEL
! 		{
! 			VariableSetStmt *n = makeNode(VariableSetStmt);
! 			n->kind = VAR_RESET;
! 			n->name = "transaction_isolation";
! 			$$ = (Node *) n;
! 		}
! 	| RESET SESSION AUTHORIZATION
! 		{
! 			VariableSetStmt *n = makeNode(VariableSetStmt);
! 			n->kind = VAR_RESET;
! 			n->name = "session_authorization";
! 			$$ = (Node *) n;
! 		}
! 	;
! 
! reset_common:
! 		var_name
! 			{
! 				VariableSetStmt *n = makeNode(VariableSetStmt);
! 				n->kind = VAR_RESET;
! 				n->name = $1;
! 				$$ = n;
! 			}
! 		| TIME ZONE
! 			{
! 				VariableSetStmt *n = makeNode(VariableSetStmt);
! 				n->kind = VAR_RESET;
! 				n->name = "timezone";
! 				$$ = n;
! 			}
! 		| ALL
! 			{
! 				VariableSetStmt *n = makeNode(VariableSetStmt);
! 				n->kind = VAR_RESET_ALL;
! 				$$ = n;
! 			}
! 	;
  
  /* SetResetClause allows SET or RESET without LOCAL */
  SetResetClause:
***************
*** 12844,12849 **** reserved_keyword:
--- 12869,12875 ----
  			| ONLY
  			| OR
  			| ORDER
+ 			| PERSISTENT
  			| PLACING
  			| PRIMARY
  			| REFERENCES
*** a/src/backend/postmaster/postmaster.c
--- b/src/backend/postmaster/postmaster.c
***************
*** 2398,2403 **** reaper(SIGNAL_ARGS)
--- 2398,2415 ----
  				continue;
  			}
  
+ 			/* Delete the postgresql.auto.conf.lock file if exists */
+ 			{
+ 				char		LockFileName[MAXPGPATH];
+ 
+ 				strlcpy(LockFileName, ConfigFileName, sizeof(LockFileName));
+ 				get_parent_directory(LockFileName);
+ 				join_path_components(LockFileName, LockFileName, AutoConfigLockFilename);
+ 				canonicalize_path(LockFileName);
+ 
+ 				unlink(LockFileName);
+ 			}
+ 
  			/*
  			 * Startup succeeded, commence normal operations
  			 */
*** a/src/backend/replication/basebackup.c
--- b/src/backend/replication/basebackup.c
***************
*** 581,586 **** sendDir(char *path, int basepathlen, bool sizeonly)
--- 581,592 ----
  					strlen(PG_TEMP_FILE_PREFIX)) == 0)
  			continue;
  
+ 		/* skip lock files used in postgresql.auto.conf edit */
+ 		if (strncmp(de->d_name,
+ 					"postgresql.auto.conf.lock",
+ 					strlen("postgresql.auto.conf.lock")) == 0)
+ 			continue;
+ 
  		/*
  		 * If there's a backup_label file, it belongs to a backup started by
  		 * the user with pg_start_backup(). It is *not* correct for this
*** a/src/backend/utils/misc/guc-file.l
--- b/src/backend/utils/misc/guc-file.l
***************
*** 41,46 **** enum {
--- 41,47 ----
  	GUC_ERROR = 100
  };
  
+ static bool is_config_dir_parsed = false;
  static unsigned int ConfigFileLineno;
  static const char *GUC_flex_fatal_errmsg;
  static sigjmp_buf *GUC_flex_fatal_jmp;
***************
*** 137,142 **** ProcessConfigFile(GucContext context)
--- 138,145 ----
  	/* Parse the file into a list of option names and values */
  	head = tail = NULL;
  
+ 	is_config_dir_parsed = false;
+ 
  	if (!ParseConfigFile(ConfigFileName, NULL, true, 0, elevel, &head, &tail))
  	{
  		/* Syntax error(s) detected in the file, so bail out */
***************
*** 144,149 **** ProcessConfigFile(GucContext context)
--- 147,159 ----
  		goto cleanup_list;
  	}
  
+ 	if (!is_config_dir_parsed)
+ 	{
+ 		ereport(WARNING,
+ 				(errmsg("Default \"config_dir\" is not present in postgresql.conf."
+ 						"Any configuration value changed with SET PERSISTENT command will not be effective.")));
+ 	}
+ 
  	/*
  	 * Mark all extant GUC variables as not present in the config file.
  	 * We need this so that we can tell below which ones have been removed
***************
*** 367,373 **** ProcessConfigFile(GucContext context)
   * path, return an absolute one.  We consider the location to be relative to
   * the directory holding the calling file.
   */
! static char *
  AbsoluteConfigLocation(const char *location, const char *calling_file)
  {
  	char		abs_path[MAXPGPATH];
--- 377,383 ----
   * path, return an absolute one.  We consider the location to be relative to
   * the directory holding the calling file.
   */
! char *
  AbsoluteConfigLocation(const char *location, const char *calling_file)
  {
  	char		abs_path[MAXPGPATH];
***************
*** 411,416 **** ParseConfigFile(const char *config_file, const char *calling_file, bool strict,
--- 421,427 ----
  {
  	bool		OK = true;
  	FILE	   *fp;
+ 	char 		*ConfigAutoFileName;
  
  	/*
  	 * Reject too-deep include nesting depth.  This is just a safety check
***************
*** 427,432 **** ParseConfigFile(const char *config_file, const char *calling_file, bool strict,
--- 438,449 ----
  	}
  
  	config_file = AbsoluteConfigLocation(config_file,calling_file);
+ 
+ 	/* Checking for the postgresql.auto.conf file is parsed or not */
+ 	ConfigAutoFileName = AbsoluteConfigLocation(AutoConfigFileName, ConfigFileName);
+ 	if (depth == 1 && strcmp(ConfigAutoFileName, config_file) == 0)
+ 		is_config_dir_parsed = true;
+ 
  	fp = AllocateFile(config_file, "r");
  	if (!fp)
  	{
***************
*** 533,538 **** ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
--- 550,556 ----
  	{
  		char	   *opt_name = NULL;
  		char	   *opt_value = NULL;
+ 		bool		is_string = false;
  		ConfigVariable *item;
  
  		if (token == GUC_EOL)	/* empty or comment line */
***************
*** 556,562 **** ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
--- 574,583 ----
  			token != GUC_UNQUOTED_STRING)
  			goto parse_error;
  		if (token == GUC_STRING)	/* strip quotes and escapes */
+ 		{
  			opt_value = GUC_scanstr(yytext);
+ 			is_string = true;
+ 		}
  		else
  			opt_value = pstrdup(yytext);
  
***************
*** 620,625 **** ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
--- 641,647 ----
  			item = palloc(sizeof *item);
  			item->name = opt_name;
  			item->value = opt_value;
+ 			item->is_quoted = is_string;
  			item->filename = pstrdup(config_file);
  			item->sourceline = ConfigFileLineno-1;
  			item->next = NULL;
*** a/src/backend/utils/misc/guc.c
--- b/src/backend/utils/misc/guc.c
***************
*** 3356,3364 **** static void reapply_stacked_values(struct config_generic * variable,
--- 3356,3370 ----
  					   GucContext curscontext, GucSource cursource);
  static void ShowGUCConfigOption(const char *name, DestReceiver *dest);
  static void ShowAllGUCConfig(DestReceiver *dest);
+ static void value_to_string_withunits(int value, int flags, char *buffer, int buflen);
  static char *_ShowOption(struct config_generic * record, bool use_units);
  static bool validate_option_array_item(const char *name, const char *value,
  						   bool skipIfNoPermissions);
+ static int	create_conf_lock_file(const char *LockFileName);
+ static void write_auto_conf_file(int fd, ConfigVariable **head_p);
+ static void replace_auto_config_value(ConfigVariable **head_p, ConfigVariable **tail_p,
+ 				 char *config_file, char *name, char *value, bool is_quoted);
+ static void set_config_file(VariableSetStmt *setstmt);
  
  
  /*
***************
*** 4131,4136 **** SelectConfigFiles(const char *userDoption, const char *progname)
--- 4137,4151 ----
  		return false;
  	}
  
+ 	/* Remove postgresql.auto.conf.lock file make be left over from last crash */
+ 	if (!IsUnderPostmaster)
+ 	{
+ 		char	   *LockFileName;
+ 
+ 		LockFileName = AbsoluteConfigLocation(AutoConfigLockFilename, ConfigFileName);
+ 		unlink(LockFileName);
+ 	}
+ 
  	ProcessConfigFile(PGC_POSTMASTER);
  
  	/*
***************
*** 4719,4725 **** AtEOXact_GUC(bool isCommit, int nestLevel)
  	GUCNestLevel = nestLevel - 1;
  }
  
- 
  /*
   * Start up automatic reporting of changes to variables marked GUC_REPORT.
   * This is executed at completion of backend startup.
--- 4734,4739 ----
***************
*** 5105,5110 **** config_enum_get_options(struct config_enum * record, const char *prefix,
--- 5119,5370 ----
  	return retstr.data;
  }
  
+ /*
+  * Validates configuration parameter and value, incase of source is default
+  * returns the default value in string format.
+  */
+ struct config_generic *
+ validate_conf_option(const char *name, char **value, GucSource source)
+ {
+ 	struct config_generic *record;
+ 
+ 	record = find_option(name, true, LOG);
+ 	if (record == NULL)
+ 	{
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_UNDEFINED_OBJECT),
+ 			   errmsg("unrecognized configuration parameter \"%s\"", name)));
+ 	}
+ 
+ 	if (record->context == PGC_INTERNAL)
+ 	{
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
+ 				 errmsg("parameter \"%s\" cannot be changed",
+ 						name)));
+ 	}
+ 
+ 	/*
+ 	 * Evaluate value and set variable.
+ 	 */
+ 	switch (record->vartype)
+ 	{
+ 
+ 		case PGC_BOOL:
+ 			{
+ 				struct config_bool *conf = (struct config_bool *) record;
+ 				bool		newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (*value)
+ 				{
+ 					if (!parse_bool(*value, &newval))
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						  errmsg("parameter \"%s\" requires a Boolean value",
+ 								 name)));
+ 					}
+ 					if (!call_bool_check_hook(conf, &newval, &newextra,
+ 											  source, LOG))
+ 						return NULL;
+ 				}
+ 				else if (source == PGC_S_DEFAULT)
+ 				{
+ 					newval = conf->boot_val;
+ 					if (!call_bool_check_hook(conf, &newval, &newextra,
+ 											  source, LOG))
+ 						return NULL;
+ 					*value = pstrdup(newval ? "on" : "off");
+ 				}
+ 			}
+ 			break;
+ 		case PGC_INT:
+ 			{
+ 				struct config_int *conf = (struct config_int *) record;
+ 				int			newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (*value)
+ 				{
+ 					const char *hintmsg;
+ 
+ 					if (!parse_int(*value, &newval, conf->gen.flags, &hintmsg))
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						 errmsg("invalid value for parameter \"%s\": \"%s\"",
+ 								name, *value),
+ 								 hintmsg ? errhint("%s", _(hintmsg)) : 0));
+ 					}
+ 					if (newval < conf->min || newval > conf->max)
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 								 errmsg("%d is outside the valid range for parameter \"%s\" (%d .. %d)",
+ 										newval, name, conf->min, conf->max)));
+ 					}
+ 					if (!call_int_check_hook(conf, &newval, &newextra,
+ 											 source, LOG))
+ 						return NULL;
+ 				}
+ 				else if (source == PGC_S_DEFAULT)
+ 				{
+ 					char		buffer[256];
+ 
+ 					newval = conf->boot_val;
+ 					if (!call_int_check_hook(conf, &newval, &newextra,
+ 											 source, LOG))
+ 						return NULL;
+ 
+ 					value_to_string_withunits(newval, record->flags, buffer, sizeof(buffer));
+ 					*value = pstrdup(buffer);
+ 				}
+ 			}
+ 			break;
+ 		case PGC_REAL:
+ 			{
+ 				struct config_real *conf = (struct config_real *) record;
+ 				double		newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (*value)
+ 				{
+ 					if (!parse_real(*value, &newval))
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						  errmsg("parameter \"%s\" requires a numeric value",
+ 								 name)));
+ 					}
+ 					if (newval < conf->min || newval > conf->max)
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 								 errmsg("%g is outside the valid range for parameter \"%s\" (%g .. %g)",
+ 										newval, name, conf->min, conf->max)));
+ 					}
+ 					if (!call_real_check_hook(conf, &newval, &newextra,
+ 											  source, LOG))
+ 						return NULL;
+ 				}
+ 				else if (source == PGC_S_DEFAULT)
+ 				{
+ 					char		buffer[256];
+ 
+ 					newval = conf->boot_val;
+ 					if (!call_real_check_hook(conf, &newval, &newextra,
+ 											  source, LOG))
+ 						return NULL;
+ 
+ 					snprintf(buffer, sizeof(buffer), "%g", newval);
+ 					*value = pstrdup(buffer);
+ 				}
+ 			}
+ 			break;
+ 		case PGC_STRING:
+ 			{
+ 				struct config_string *conf = (struct config_string *) record;
+ 				char	   *newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (*value)
+ 				{
+ 					/*
+ 					 * The value passed by the caller could be transient, so
+ 					 * we always strdup it.
+ 					 */
+ 					newval = guc_strdup(LOG, *value);
+ 					if (newval == NULL)
+ 						return NULL;
+ 
+ 					/*
+ 					 * The only built-in "parsing" check we have is to apply
+ 					 * truncation if GUC_IS_NAME.
+ 					 */
+ 					if (conf->gen.flags & GUC_IS_NAME)
+ 						truncate_identifier(newval, strlen(newval), true);
+ 
+ 					if (!call_string_check_hook(conf, &newval, &newextra,
+ 												source, LOG))
+ 					{
+ 						free(newval);
+ 						return NULL;
+ 					}
+ 				}
+ 				else if (source == PGC_S_DEFAULT)
+ 				{
+ 					if (conf->boot_val != NULL)
+ 					{
+ 						newval = guc_strdup(LOG, conf->boot_val);
+ 						if (newval == NULL)
+ 							return NULL;
+ 					}
+ 					else
+ 						newval = NULL;
+ 
+ 					if (!call_string_check_hook(conf, &newval, &newextra,
+ 												source, LOG))
+ 					{
+ 						free(newval);
+ 						return NULL;
+ 					}
+ 
+ 					if (newval)
+ 					{
+ 						*value = pstrdup(newval);
+ 						free(newval);
+ 					}
+ 				}
+ 			}
+ 			break;
+ 		case PGC_ENUM:
+ 			{
+ 				struct config_enum *conf = (struct config_enum *) record;
+ 				int			newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (*value)
+ 				{
+ 					if (!config_enum_lookup_by_name(conf, *value, &newval))
+ 					{
+ 						char	   *hintmsg;
+ 
+ 						hintmsg = config_enum_get_options(conf,
+ 														"Available values: ",
+ 														  ".", ", ");
+ 
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						 errmsg("invalid value for parameter \"%s\": \"%s\"",
+ 								name, *value),
+ 								 hintmsg ? errhint("%s", _(hintmsg)) : 0));
+ 
+ 						if (hintmsg)
+ 							pfree(hintmsg);
+ 						return 0;
+ 					}
+ 					if (!call_enum_check_hook(conf, &newval, &newextra,
+ 											  PGC_S_FILE, LOG))
+ 						return 0;
+ 				}
+ 				else if (source == PGC_S_DEFAULT)
+ 				{
+ 					newval = conf->boot_val;
+ 					if (!call_enum_check_hook(conf, &newval, &newextra,
+ 											  PGC_S_DEFAULT, LOG))
+ 						return NULL;
+ 
+ 					*value = pstrdup(config_enum_lookup_by_value(
+ 											   (struct config_enum *) record,
+ 																 newval));
+ 				}
+ 			}
+ 	}
+ 
+ 	return record;
+ }
+ 
  
  /*
   * Sets option `name' to given value.
***************
*** 5908,5913 **** set_config_sourcefile(const char *name, char *sourcefile, int sourceline)
--- 6168,6487 ----
  }
  
  /*
+  * Creates auto conf lock file used for protecting parallel modification of
+  * postgresql.auto.conf file.
+  */
+ static int
+ create_conf_lock_file(const char *LockFileName)
+ {
+ 	int			fd;
+ 	int			ntries;
+ 
+ 	/*
+ 	 * We need a loop here because of race conditions. Retry for 100 times.
+ 	 */
+ 	for (ntries = 0;; ntries++)
+ 	{
+ 		fd = open(LockFileName, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
+ 		if (fd >= 0)
+ 			break;
+ 
+ 		/*
+ 		 * Couldn't create the lock file. Probably it already exists. If so
+ 		 * wait for some time
+ 		 */
+ 		if ((errno != EEXIST && errno != EACCES) || ntries > 100)
+ 		{
+ 			if (errno != EEXIST)
+ 			{
+ 				ereport(ERROR,
+ 						(errcode_for_file_access(),
+ 						 errmsg("could not create lock file \"%s\": %m",
+ 								LockFileName)));
+ 			}
+ 			else
+ 			{
+ 				ereport(ERROR,
+ 						(errcode_for_file_access(),
+ 						 errmsg("could not create lock file \"%s\": %m ", LockFileName),
+ 						 errhint("May be too many concurrent edit into file happening, please wait!! and retry"
+ 								 "or .lock is file accidently left there please clean the file from config_dir")));
+ 			}
+ 		}
+ 		else
+ 		{
+ 			pg_usleep(100000);	/* in total wait for 10sec */
+ 		}
+ 	}
+ 
+ 	return fd;
+ }
+ 
+ 
+ /* Write updated configuration parameter values into postgresql.auto.conf.lock */
+ static void
+ write_auto_conf_file(int fd, ConfigVariable **head_p)
+ {
+ 	ConfigVariable *item;
+ 	StringInfoData buf;
+ 
+ 	initStringInfo(&buf);
+ 
+ 	for (item = *head_p; item != NULL; item = item->next)
+ 	{
+ 		appendStringInfoString(&buf, item->name);
+ 		appendStringInfoString(&buf, " = ");
+ 
+ 		if (true == item->is_quoted)
+ 		{
+ 			appendStringInfoString(&buf, "\'");
+ 			appendStringInfoString(&buf, item->value);
+ 			appendStringInfoString(&buf, "\'");
+ 		}
+ 		else
+ 		{
+ 			appendStringInfoString(&buf, item->value);
+ 		}
+ 
+ 		appendStringInfoString(&buf, "\n");
+ 
+ 		if (write(fd, buf.data, buf.len) < 0)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("failed to write into to \"postgresql.auto.conf.lock\" file")));
+ 		}
+ 
+ 		resetStringInfo(&buf);
+ 	}
+ 
+ 	if (pg_fsync(fd) != 0)
+ 		ereport(ERROR,
+ 				(errcode_for_file_access(),
+ 		  errmsg("could not fsync file \"postgresql.auto.conf.lock\": %m")));
+ 
+ 
+ 	pfree(buf.data);
+ 	return;
+ }
+ 
+ 
+ /*
+  * Replace the updated configuration parameter value in postgresql.auto.conf
+  * file lines. If it is new then append extra line at the end of lines.
+  */
+ static void
+ replace_auto_config_value(ConfigVariable **head_p, ConfigVariable **tail_p,
+ 						  char *config_file, char *name, char *value,
+ 						  bool is_quoted)
+ {
+ 	ConfigVariable *item,
+ 			   *prev = NULL;
+ 
+ 	if (NULL != *head_p)
+ 	{
+ 		for (item = *head_p; item != NULL; item = item->next)
+ 		{
+ 			if (strcmp(item->name, name) == 0)
+ 			{
+ 				pfree(item->value);
+ 				if (value)
+ 				{
+ 					/* update the parameter value */
+ 					item->value = pstrdup(value);
+ 				}
+ 				else
+ 				{
+ 					/* delete the configuration parameter from list */
+ 					if (*head_p == item)
+ 					{
+ 						*head_p = item->next;
+ 					}
+ 					else
+ 					{
+ 						prev->next = item->next;
+ 					}
+ 
+ 					if (*tail_p == item)
+ 					{
+ 						*tail_p = prev;
+ 					}
+ 					pfree(item->name);
+ 					pfree(item->filename);
+ 					pfree(item);
+ 				}
+ 				return;
+ 			}
+ 			prev = item;
+ 		}
+ 	}
+ 
+ 	if (NULL == value)
+ 	{
+ 		return;
+ 	}
+ 
+ 	item = palloc(sizeof *item);
+ 	item->name = pstrdup(name);
+ 	item->value = pstrdup(value);
+ 	item->is_quoted = is_quoted;
+ 	item->filename = pstrdup(config_file);
+ 	item->next = NULL;
+ 
+ 	if (*head_p == NULL)
+ 	{
+ 		item->sourceline = 1;
+ 		*head_p = item;
+ 	}
+ 	else
+ 	{
+ 		item->sourceline = (*tail_p)->sourceline + 1;
+ 		(*tail_p)->next = item;
+ 	}
+ 
+ 	*tail_p = item;
+ 
+ 	return;
+ }
+ 
+ 
+ /*
+  * Persist the configuration parameter value.
+  * Writes the value of configuration parameter in postgresql.auto.conf.lock file.
+  * .lock file is used to disallow changing of file by multiple backends.
+  * On Success, rename postgresql.auto.conf.lock to postgresql.auto.conf
+  * and On Failure, delete the postgresql.auto.conf.lock
+  */
+ static void
+ set_config_file(VariableSetStmt *setstmt)
+ {
+ 	char	   *name;
+ 	char	   *value;
+ 	int			lockfd = -1;
+ 	FILE	   *infile;
+ 	struct config_generic *record;
+ 	ConfigVariable *head_p = NULL;
+ 	ConfigVariable *tail_p = NULL;
+ 	char	   *ConfAutoFileName;
+ 	char	   *LockFileName;
+ 	bool		is_resetall = false;
+ 	GucSource	source = PGC_S_FILE;
+ 	struct stat st;
+ 
+ 	if (!superuser())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+ 				 (errmsg("must be superuser to execute SET/RESET PERSISTENT command"))));
+ 
+ 	if (IsTransactionBlock())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_ACTIVE_SQL_TRANSACTION),
+ 				 (errmsg("SET/RESET PERSISTENT command cannot run inside a transaction block"))));
+ 
+ 	/*
+ 	 * Validate the name and arguments [value1, value2 ... ].
+ 	 */
+ 	name = setstmt->name;
+ 
+ 	switch (setstmt->kind)
+ 	{
+ 		case VAR_SET_VALUE:
+ 			value = ExtractSetVariableArgs(setstmt);
+ 			break;
+ 
+ 		case VAR_SET_DEFAULT:
+ 			value = NULL;
+ 			source = PGC_S_DEFAULT;
+ 			break;
+ 
+ 		case VAR_RESET:
+ 			value = NULL;
+ 			break;
+ 
+ 		case VAR_RESET_ALL:
+ 			is_resetall = true;
+ 			break;
+ 
+ 		default:
+ 			return;
+ 	}
+ 
+ 	if (!is_resetall)
+ 	{
+ 		record = validate_conf_option(name, &value, source);
+ 		if (!record)
+ 			ereport(ERROR,
+ 					(errmsg("invalid value for parameter \"%s\": \"%s\"", name, value)));
+ 	}
+ 
+ 	/* Create the postgresql.auto.conf.lock file */
+ 	ConfAutoFileName = AbsoluteConfigLocation(AutoConfigFileName, ConfigFileName);
+ 	LockFileName = AbsoluteConfigLocation(AutoConfigLockFilename, ConfigFileName);
+ 
+ 	lockfd = create_conf_lock_file(LockFileName);
+ 
+ 	PG_TRY();
+ 	{
+ 		if (stat(ConfAutoFileName, &st) != 0)
+ 		{
+ 			int			fd;
+ 
+ 			fd = open(ConfAutoFileName, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
+ 			if (fd < 0)
+ 				ereport(ERROR,
+ 						(errcode_for_file_access(),
+ 						 errmsg("creation of auto conf file failed as it was not exist\"%s\": %m",
+ 								ConfAutoFileName)));
+ 			close(fd);
+ 
+ 			ereport(NOTICE,
+ 				 (errmsg("Created auto conf file as it was not exist \"%s\"",
+ 						 ConfAutoFileName)));
+ 		}
+ 
+ 		if (!is_resetall)
+ 		{
+ 			/* open postgresql.auto.conf file */
+ 			infile = AllocateFile(ConfAutoFileName, "r");
+ 			if (infile == NULL)
+ 				ereport(ERROR,
+ 				   (errmsg("failed to open \"postgresql.auto.conf\" file")));
+ 
+ 			/* Parse the postgresql.auto.conf file */
+ 			ParseConfigFp(infile, ConfAutoFileName, 0, LOG, &head_p, &tail_p);
+ 
+ 			FreeFile(infile);
+ 
+ 			/* replace with new value */
+ 			replace_auto_config_value(&head_p, &tail_p, ConfAutoFileName, name,
+ 					  value, (record->vartype == PGC_STRING) ? true : false);
+ 
+ 			/* Write the New contents to postgresql.auto.conf.lock file */
+ 			write_auto_conf_file(lockfd, &head_p);
+ 		}
+ 
+ 		close(lockfd);
+ 		lockfd = -1;
+ 
+ 		if (rename(LockFileName, ConfAutoFileName) < 0)
+ 			ereport(ERROR,
+ 					(errcode_for_file_access(),
+ 					 errmsg("could not rename file \"%s\" to \"%s\" : %m",
+ 							LockFileName, ConfAutoFileName)));
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		if (lockfd >= 0)
+ 			close(lockfd);
+ 
+ 		unlink(LockFileName);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 	return;
+ }
+ 
+ 
+ /*
   * Set a config option to the given value.
   *
   * See also set_config_option; this is just the wrapper to be called from
***************
*** 6037,6043 **** GetConfigOptionResetString(const char *name)
  	return NULL;
  }
  
- 
  /*
   * flatten_set_variable_args
   *		Given a parsenode List as emitted by the grammar for SET,
--- 6611,6616 ----
***************
*** 6178,6183 **** ExecSetVariableStmt(VariableSetStmt *stmt)
--- 6751,6762 ----
  	switch (stmt->kind)
  	{
  		case VAR_SET_VALUE:
+ 			if (stmt->is_persistent)
+ 			{
+ 				set_config_file(stmt);
+ 				break;
+ 			}
+ 			/* FALLTHROUGH */
  		case VAR_SET_CURRENT:
  			(void) set_config_option(stmt->name,
  									 ExtractSetVariableArgs(stmt),
***************
*** 6258,6273 **** ExecSetVariableStmt(VariableSetStmt *stmt)
  			break;
  		case VAR_SET_DEFAULT:
  		case VAR_RESET:
! 			(void) set_config_option(stmt->name,
! 									 NULL,
  									 (superuser() ? PGC_SUSET : PGC_USERSET),
! 									 PGC_S_SESSION,
! 									 action,
! 									 true,
! 									 0);
  			break;
  		case VAR_RESET_ALL:
! 			ResetAllOptions();
  			break;
  	}
  }
--- 6837,6858 ----
  			break;
  		case VAR_SET_DEFAULT:
  		case VAR_RESET:
! 			if (stmt->is_persistent)
! 				set_config_file(stmt);
! 			else
! 				(void) set_config_option(stmt->name,
! 										 NULL,
  									 (superuser() ? PGC_SUSET : PGC_USERSET),
! 										 PGC_S_SESSION,
! 										 action,
! 										 true,
! 										 0);
  			break;
  		case VAR_RESET_ALL:
! 			if (stmt->is_persistent)
! 				set_config_file(stmt);
! 			else
! 				ResetAllOptions();
  			break;
  	}
  }
***************
*** 7320,7325 **** show_all_settings(PG_FUNCTION_ARGS)
--- 7905,7993 ----
  	}
  }
  
+ /*
+  * Returns the converted integer value as string with units added.
+  */
+ static void
+ value_to_string_withunits(int value, int flags, char *buffer, int buflen)
+ {
+ 	/*
+ 	 * Use int64 arithmetic to avoid overflows in units conversion.
+ 	 */
+ 	int64		result = value;
+ 	const char *unit;
+ 
+ 	if (result > 0 && (flags & GUC_UNIT_MEMORY))
+ 	{
+ 		switch (flags & GUC_UNIT_MEMORY)
+ 		{
+ 			case GUC_UNIT_BLOCKS:
+ 				result *= BLCKSZ / 1024;
+ 				break;
+ 			case GUC_UNIT_XBLOCKS:
+ 				result *= XLOG_BLCKSZ / 1024;
+ 				break;
+ 		}
+ 
+ 		if (result % KB_PER_GB == 0)
+ 		{
+ 			result /= KB_PER_GB;
+ 			unit = "GB";
+ 		}
+ 		else if (result % KB_PER_MB == 0)
+ 		{
+ 			result /= KB_PER_MB;
+ 			unit = "MB";
+ 		}
+ 		else
+ 		{
+ 			unit = "kB";
+ 		}
+ 	}
+ 	else if (result > 0 && (flags & GUC_UNIT_TIME))
+ 	{
+ 		switch (flags & GUC_UNIT_TIME)
+ 		{
+ 			case GUC_UNIT_S:
+ 				result *= MS_PER_S;
+ 				break;
+ 			case GUC_UNIT_MIN:
+ 				result *= MS_PER_MIN;
+ 				break;
+ 		}
+ 
+ 		if (result % MS_PER_D == 0)
+ 		{
+ 			result /= MS_PER_D;
+ 			unit = "d";
+ 		}
+ 		else if (result % MS_PER_H == 0)
+ 		{
+ 			result /= MS_PER_H;
+ 			unit = "h";
+ 		}
+ 		else if (result % MS_PER_MIN == 0)
+ 		{
+ 			result /= MS_PER_MIN;
+ 			unit = "min";
+ 		}
+ 		else if (result % MS_PER_S == 0)
+ 		{
+ 			result /= MS_PER_S;
+ 			unit = "s";
+ 		}
+ 		else
+ 		{
+ 			unit = "ms";
+ 		}
+ 	}
+ 	else
+ 		unit = "";
+ 
+ 	snprintf(buffer, buflen, INT64_FORMAT "%s", result, unit);
+ }
+ 
+ 
  static char *
  _ShowOption(struct config_generic * record, bool use_units)
  {
***************
*** 7347,7430 **** _ShowOption(struct config_generic * record, bool use_units)
  					val = (*conf->show_hook) ();
  				else
  				{
! 					/*
! 					 * Use int64 arithmetic to avoid overflows in units
! 					 * conversion.
! 					 */
! 					int64		result = *conf->variable;
! 					const char *unit;
! 
! 					if (use_units && result > 0 &&
! 						(record->flags & GUC_UNIT_MEMORY))
! 					{
! 						switch (record->flags & GUC_UNIT_MEMORY)
! 						{
! 							case GUC_UNIT_BLOCKS:
! 								result *= BLCKSZ / 1024;
! 								break;
! 							case GUC_UNIT_XBLOCKS:
! 								result *= XLOG_BLCKSZ / 1024;
! 								break;
! 						}
! 
! 						if (result % KB_PER_GB == 0)
! 						{
! 							result /= KB_PER_GB;
! 							unit = "GB";
! 						}
! 						else if (result % KB_PER_MB == 0)
! 						{
! 							result /= KB_PER_MB;
! 							unit = "MB";
! 						}
! 						else
! 						{
! 							unit = "kB";
! 						}
! 					}
! 					else if (use_units && result > 0 &&
! 							 (record->flags & GUC_UNIT_TIME))
! 					{
! 						switch (record->flags & GUC_UNIT_TIME)
! 						{
! 							case GUC_UNIT_S:
! 								result *= MS_PER_S;
! 								break;
! 							case GUC_UNIT_MIN:
! 								result *= MS_PER_MIN;
! 								break;
! 						}
! 
! 						if (result % MS_PER_D == 0)
! 						{
! 							result /= MS_PER_D;
! 							unit = "d";
! 						}
! 						else if (result % MS_PER_H == 0)
! 						{
! 							result /= MS_PER_H;
! 							unit = "h";
! 						}
! 						else if (result % MS_PER_MIN == 0)
! 						{
! 							result /= MS_PER_MIN;
! 							unit = "min";
! 						}
! 						else if (result % MS_PER_S == 0)
! 						{
! 							result /= MS_PER_S;
! 							unit = "s";
! 						}
! 						else
! 						{
! 							unit = "ms";
! 						}
! 					}
! 					else
! 						unit = "";
! 
! 					snprintf(buffer, sizeof(buffer), INT64_FORMAT "%s",
! 							 result, unit);
  					val = buffer;
  				}
  			}
--- 8015,8022 ----
  					val = (*conf->show_hook) ();
  				else
  				{
! 					value_to_string_withunits(*conf->variable,
! 					(use_units) ? record->flags : 0, buffer, sizeof(buffer));
  					val = buffer;
  				}
  			}
*** a/src/backend/utils/misc/postgresql.conf.sample
--- b/src/backend/utils/misc/postgresql.conf.sample
***************
*** 581,586 ****
--- 581,593 ----
  #include_if_exists = 'exists.conf'	# include file only if it exists
  #include = 'special.conf'		# include file
  
+ # This includes the default configuration directory included to support
+ # SET PERSISTENT statement.
+ #
+ # WARNNING: Any configuration parameter values specified after this line
+ #           will override the values set by SET PERSISTENT statement.
+ #include_dir = 'auto.conf.d'
+ 
  #------------------------------------------------------------------------------
  # CUSTOMIZED OPTIONS
  #------------------------------------------------------------------------------
*** a/src/bin/initdb/initdb.c
--- b/src/bin/initdb/initdb.c
***************
*** 1163,1168 **** setup_config(void)
--- 1163,1169 ----
  	char		repltok[MAXPGPATH];
  	char		path[MAXPGPATH];
  	const char *default_timezone;
+ 	FILE	   *autofile;
  
  	fputs(_("creating configuration files ... "), stdout);
  	fflush(stdout);
***************
*** 1245,1255 **** setup_config(void)
--- 1246,1279 ----
  		conflines = replace_token(conflines, "#log_timezone = 'GMT'", repltok);
  	}
  
+ 	snprintf(repltok, sizeof(repltok), "include_dir = 'config_dir'");
+ 	conflines = replace_token(conflines, "#include_dir = 'auto.conf.d'", repltok);
+ 
  	snprintf(path, sizeof(path), "%s/postgresql.conf", pg_data);
  
  	writefile(path, conflines);
  	chmod(path, S_IRUSR | S_IWUSR);
  
+ 	/* create a .auto for conf file */
+ 	sprintf(path, "%s/config_dir/postgresql.auto.conf", pg_data);
+ 	autofile = fopen(path, PG_BINARY_W);
+ 	if (autofile == NULL)
+ 	{
+ 		fprintf(stderr, _("%s: could not open file \"%s\" for writing: %s\n"),
+ 				progname, path, strerror(errno));
+ 		exit_nicely();
+ 	}
+ 
+ 	if (fclose(autofile))
+ 	{
+ 		fprintf(stderr, _("%s: could not write file \"%s\": %s\n"),
+ 				progname, path, strerror(errno));
+ 		exit_nicely();
+ 	}
+ 
+ 	chmod(path, S_IRUSR | S_IWUSR);
+ 
+ 
  	free(conflines);
  
  
***************
*** 2887,2893 **** main(int argc, char *argv[])
  		"base",
  		"base/1",
  		"pg_tblspc",
! 		"pg_stat_tmp"
  	};
  
  	progname = get_progname(argv[0]);
--- 2911,2918 ----
  		"base",
  		"base/1",
  		"pg_tblspc",
! 		"pg_stat_tmp",
! 		"config_dir"
  	};
  
  	progname = get_progname(argv[0]);
*** a/src/include/nodes/parsenodes.h
--- b/src/include/nodes/parsenodes.h
***************
*** 1425,1430 **** typedef struct VariableSetStmt
--- 1425,1431 ----
  	char	   *name;			/* variable to be set */
  	List	   *args;			/* List of A_Const nodes */
  	bool		is_local;		/* SET LOCAL? */
+ 	bool		is_persistent;	/* SET PERSISTENT? */
  } VariableSetStmt;
  
  /* ----------------------
*** a/src/include/parser/kwlist.h
--- b/src/include/parser/kwlist.h
***************
*** 279,284 **** PG_KEYWORD("partial", PARTIAL, UNRESERVED_KEYWORD)
--- 279,285 ----
  PG_KEYWORD("partition", PARTITION, UNRESERVED_KEYWORD)
  PG_KEYWORD("passing", PASSING, UNRESERVED_KEYWORD)
  PG_KEYWORD("password", PASSWORD, UNRESERVED_KEYWORD)
+ PG_KEYWORD("persistent", PERSISTENT, RESERVED_KEYWORD)
  PG_KEYWORD("placing", PLACING, RESERVED_KEYWORD)
  PG_KEYWORD("plans", PLANS, UNRESERVED_KEYWORD)
  PG_KEYWORD("position", POSITION, COL_NAME_KEYWORD)
*** a/src/include/utils/guc.h
--- b/src/include/utils/guc.h
***************
*** 105,115 **** typedef struct ConfigVariable
--- 105,118 ----
  {
  	char	   *name;
  	char	   *value;
+ 	bool		is_quoted;
  	char	   *filename;
  	int			sourceline;
  	struct ConfigVariable *next;
  } ConfigVariable;
  
+ extern char *AbsoluteConfigLocation(const char *location,
+ 					   const char *calling_file);
  extern bool ParseConfigFile(const char *config_file, const char *calling_file,
  				bool strict, int depth, int elevel,
  				ConfigVariable **head_p, ConfigVariable **tail_p);
***************
*** 191,196 **** typedef enum
--- 194,203 ----
  
  #define GUC_NOT_WHILE_SEC_REST	0x8000	/* can't set if security restricted */
  
+ /* postgresql.auto.file name and its lock */
+ #define AutoConfigFileName "config_dir/postgresql.auto.conf"
+ #define AutoConfigLockFilename  "config_dir/postgresql.auto.conf.lock"
+ 
  /* GUC vars that are actually declared in guc.c, rather than elsewhere */
  extern bool log_duration;
  extern bool Debug_print_plan;
*** a/src/include/utils/guc_tables.h
--- b/src/include/utils/guc_tables.h
***************
*** 260,265 **** extern void build_guc_variables(void);
  extern const char *config_enum_lookup_by_value(struct config_enum * record, int val);
  extern bool config_enum_lookup_by_name(struct config_enum * record,
  						   const char *value, int *retval);
! 
  
  #endif   /* GUC_TABLES_H */
--- 260,266 ----
  extern const char *config_enum_lookup_by_value(struct config_enum * record, int val);
  extern bool config_enum_lookup_by_name(struct config_enum * record,
  						   const char *value, int *retval);
! extern struct config_generic *validate_conf_option(const char *name,
! 					 char **value, GucSource source);
  
  #endif   /* GUC_TABLES_H */
*** /dev/null
--- b/src/test/regress/expected/persistent.out
***************
*** 0 ****
--- 1,1206 ----
+ -- parameter which cannot be set after connection start.
+ set persistent log_connections=on;
+ -- parameter can only be set at during server start.
+ set persistent max_connections To 10;
+ set persistent wal_level = hot_standby;
+ -- parameter can set by the backend
+ set persistent authentication_timeout = 10;
+ set persistent vacuum_cost_delay To 200;
+ ERROR:  200 is outside the valid range for parameter "vacuum_cost_delay" (0 .. 100)
+ set persistent bgwriter_lru_multiplier = 3.2;
+ set persistent full_page_writes = off;
+ set persistent synchronous_commit To off;
+ set persistent synchronous_standby_names = 'standby1, standby2';
+ set persistent seq_page_cost = 0.9;
+ set persistent autovacuum_naptime To 30;
+ set persistent search_path = 'public';
+ set persistent default_tablespace = '';
+ set persistent checkpoint_timeout = 1;
+ ERROR:  1 is outside the valid range for parameter "checkpoint_timeout" (30 .. 3600)
+ set persistent checkpoint_timeout = 3700;
+ ERROR:  3700 is outside the valid range for parameter "checkpoint_timeout" (30 .. 3600)
+ set persistent checkpoint_timeout = 90;
+ set persistent restart_after_crash TO on;
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show wal_level;
+  wal_level 
+ -----------
+  minimal
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  1min
+ (1 row)
+ 
+ show vacuum_cost_delay;
+  vacuum_cost_delay 
+ -------------------
+  0
+ (1 row)
+ 
+ show bgwriter_lru_multiplier;
+  bgwriter_lru_multiplier 
+ -------------------------
+  2
+ (1 row)
+ 
+ show full_page_writes;
+  full_page_writes 
+ ------------------
+  on
+ (1 row)
+ 
+ show synchronous_commit;
+  synchronous_commit 
+ --------------------
+  on
+ (1 row)
+ 
+ show synchronous_standby_names;
+  synchronous_standby_names 
+ ---------------------------
+  
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  1
+ (1 row)
+ 
+ show autovacuum_naptime;
+  autovacuum_naptime 
+ --------------------
+  1min
+ (1 row)
+ 
+ show search_path;
+   search_path   
+ ----------------
+  "$user",public
+ (1 row)
+ 
+ show default_tablespace;
+  default_tablespace 
+ --------------------
+  
+ (1 row)
+ 
+ show checkpoint_timeout;
+  checkpoint_timeout 
+ --------------------
+  5min
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+           
+ -- reload the new configurations.
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show wal_level;
+  wal_level 
+ -----------
+  minimal
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  10s
+ (1 row)
+ 
+ show vacuum_cost_delay;
+  vacuum_cost_delay 
+ -------------------
+  0
+ (1 row)
+ 
+ show bgwriter_lru_multiplier;
+  bgwriter_lru_multiplier 
+ -------------------------
+  3.2
+ (1 row)
+ 
+ show full_page_writes;
+  full_page_writes 
+ ------------------
+  off
+ (1 row)
+ 
+ show synchronous_commit;
+  synchronous_commit 
+ --------------------
+  off
+ (1 row)
+ 
+ show synchronous_standby_names;
+  synchronous_standby_names 
+ ---------------------------
+  standby1, standby2
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show autovacuum_naptime;
+  autovacuum_naptime 
+ --------------------
+  30s
+ (1 row)
+ 
+ show search_path;
+  search_path 
+ -------------
+  public
+ (1 row)
+ 
+ show default_tablespace;
+  default_tablespace 
+ --------------------
+  
+ (1 row)
+ 
+ show checkpoint_timeout;
+  checkpoint_timeout 
+ --------------------
+  90s
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- reconnect to see the new configurations
+ \c
+ select name, setting from pg_settings where name = 'log_connections';
+       name       | setting 
+ -----------------+---------
+  log_connections | on
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'max_connections';
+       name       | setting 
+ -----------------+---------
+  max_connections | 100
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'wal_level';
+    name    | setting 
+ -----------+---------
+  wal_level | minimal
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'authentication_timeout';
+           name          | setting 
+ ------------------------+---------
+  authentication_timeout | 10
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'vacuum_cost_delay';
+        name        | setting 
+ -------------------+---------
+  vacuum_cost_delay | 0
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'bgwriter_lru_multiplier';
+           name           | setting 
+ -------------------------+---------
+  bgwriter_lru_multiplier | 3.2
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'full_page_writes';
+        name       | setting 
+ ------------------+---------
+  full_page_writes | off
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'synchronous_commit';
+         name        | setting 
+ --------------------+---------
+  synchronous_commit | off
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'synchronous_standby_names';
+            name            |      setting       
+ ---------------------------+--------------------
+  synchronous_standby_names | standby1, standby2
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'seq_page_cost';
+      name      | setting 
+ ---------------+---------
+  seq_page_cost | 0.9
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'autovacuum_naptime';
+         name        | setting 
+ --------------------+---------
+  autovacuum_naptime | 30
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'search_path';
+     name     | setting 
+ -------------+---------
+  search_path | public
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'default_tablespace';
+         name        | setting 
+ --------------------+---------
+  default_tablespace | 
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'checkpoint_timeout';
+         name        | setting 
+ --------------------+---------
+  checkpoint_timeout | 90
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'restart_after_crash';
+         name         | setting 
+ ---------------------+---------
+  restart_after_crash | on
+ (1 row)
+ 
+ -- Reset the some of the parameters which are set in above
+ set persistent log_connections = default;
+ set persistent max_connections To default;
+ set persistent authentication_timeout To default;
+ set persistent synchronous_commit = default;
+ set persistent restart_after_crash To default;
+ -- reload the new configurations.
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'log_connections';
+       name       | setting 
+ -----------------+---------
+  log_connections | on
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'max_connections';
+       name       | setting 
+ -----------------+---------
+  max_connections | 100
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'authentication_timeout';
+           name          | setting 
+ ------------------------+---------
+  authentication_timeout | 60
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'seq_page_cost';
+      name      | setting 
+ ---------------+---------
+  seq_page_cost | 0.9
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'restart_after_crash';
+         name         | setting 
+ ---------------------+---------
+  restart_after_crash | on
+ (1 row)
+ 
+ -- reconnect to see the new configurations
+ \c
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  1min
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- set the parameters again which are reset above.
+ set persistent log_connections To yes;
+ set persistent max_connections = 50;
+ set persistent authentication_timeout = 20;
+ set persistent synchronous_commit To off;
+ set persistent restart_after_crash To yes;
+ -- reload the new configurations.
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  20s
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- reconnect to see the new configurations
+ \c
+ show log_connections;
+  log_connections 
+ -----------------
+  on
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  20s
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- set a configuration param inside a function
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ set persistent enable_hashagg=off;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ select persistent_func();
+  persistent_func 
+ -----------------
+                1
+ (1 row)
+ 
+ show enable_hashagg;
+  enable_hashagg 
+ ----------------
+  on
+ (1 row)
+ 
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show enable_hashagg;
+  enable_hashagg 
+ ----------------
+  off
+ (1 row)
+ 
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ set persistent enable_hashagg=default;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ select persistent_func();
+  persistent_func 
+ -----------------
+                1
+ (1 row)
+ 
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show enable_hashagg;
+  enable_hashagg 
+ ----------------
+  on
+ (1 row)
+ 
+ Drop function persistent_func();
+ -- Reset all parameters which are set at above.
+ set persistent log_connections To default;
+ set persistent max_connections = default;
+ set persistent wal_level To default;
+ set persistent authentication_timeout To default;
+ set persistent vacuum_cost_delay = default;
+ set persistent bgwriter_lru_multiplier To default;
+ set persistent full_page_writes To default;
+ set persistent synchronous_commit = default;
+ set persistent synchronous_standby_names To default;
+ set persistent seq_page_cost To default;
+ set persistent autovacuum_naptime = default;
+ set persistent search_path To default;
+ set persistent default_tablespace To default;
+ set persistent checkpoint_timeout To default;
+ set persistent restart_after_crash = default;
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ -- Normal user tries to set
+ create user test password 'test';
+ SET SESSION AUTHORIZATION test;
+ set persistent enable_seqscan=off;
+ ERROR:  must be superuser to execute SET/RESET PERSISTENT command
+ \c -
+ drop user test;
+ -- In a transaction block tries to set
+ start transaction;
+ set persistent enable_hashagg=off;
+ ERROR:  SET/RESET PERSISTENT command cannot run inside a transaction block
+ commit;
+ start transaction;
+ set persistent enable_hashagg=default;
+ ERROR:  SET/RESET PERSISTENT command cannot run inside a transaction block
+ commit;
+ -- parameter which cannot be set after connection start.
+ set persistent log_connections=on;
+ -- parameter can only be set at during server start.
+ set persistent max_connections To 10;
+ set persistent wal_level = hot_standby;
+ -- parameter can set by the backend
+ set persistent authentication_timeout = 10;
+ set persistent vacuum_cost_delay To 200;
+ ERROR:  200 is outside the valid range for parameter "vacuum_cost_delay" (0 .. 100)
+ set persistent bgwriter_lru_multiplier = 3.2;
+ set persistent full_page_writes = off;
+ set persistent synchronous_commit To off;
+ set persistent synchronous_standby_names = 'standby1, standby2';
+ set persistent seq_page_cost = 0.9;
+ set persistent autovacuum_naptime To 30;
+ set persistent search_path = 'public';
+ set persistent default_tablespace = '';
+ set persistent checkpoint_timeout = 1;
+ ERROR:  1 is outside the valid range for parameter "checkpoint_timeout" (30 .. 3600)
+ set persistent checkpoint_timeout = 3700;
+ ERROR:  3700 is outside the valid range for parameter "checkpoint_timeout" (30 .. 3600)
+ set persistent checkpoint_timeout = 90;
+ set persistent restart_after_crash TO on;
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show wal_level;
+  wal_level 
+ -----------
+  minimal
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  1min
+ (1 row)
+ 
+ show vacuum_cost_delay;
+  vacuum_cost_delay 
+ -------------------
+  0
+ (1 row)
+ 
+ show bgwriter_lru_multiplier;
+  bgwriter_lru_multiplier 
+ -------------------------
+  2
+ (1 row)
+ 
+ show full_page_writes;
+  full_page_writes 
+ ------------------
+  on
+ (1 row)
+ 
+ show synchronous_commit;
+  synchronous_commit 
+ --------------------
+  on
+ (1 row)
+ 
+ show synchronous_standby_names;
+  synchronous_standby_names 
+ ---------------------------
+  
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  1
+ (1 row)
+ 
+ show autovacuum_naptime;
+  autovacuum_naptime 
+ --------------------
+  1min
+ (1 row)
+ 
+ show search_path;
+   search_path   
+ ----------------
+  "$user",public
+ (1 row)
+ 
+ show default_tablespace;
+  default_tablespace 
+ --------------------
+  
+ (1 row)
+ 
+ show checkpoint_timeout;
+  checkpoint_timeout 
+ --------------------
+  5min
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+           
+ -- reload the new configurations.
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show wal_level;
+  wal_level 
+ -----------
+  minimal
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  10s
+ (1 row)
+ 
+ show vacuum_cost_delay;
+  vacuum_cost_delay 
+ -------------------
+  0
+ (1 row)
+ 
+ show bgwriter_lru_multiplier;
+  bgwriter_lru_multiplier 
+ -------------------------
+  3.2
+ (1 row)
+ 
+ show full_page_writes;
+  full_page_writes 
+ ------------------
+  off
+ (1 row)
+ 
+ show synchronous_commit;
+  synchronous_commit 
+ --------------------
+  off
+ (1 row)
+ 
+ show synchronous_standby_names;
+  synchronous_standby_names 
+ ---------------------------
+  standby1, standby2
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show autovacuum_naptime;
+  autovacuum_naptime 
+ --------------------
+  30s
+ (1 row)
+ 
+ show search_path;
+  search_path 
+ -------------
+  public
+ (1 row)
+ 
+ show default_tablespace;
+  default_tablespace 
+ --------------------
+  
+ (1 row)
+ 
+ show checkpoint_timeout;
+  checkpoint_timeout 
+ --------------------
+  90s
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- reconnect to see the new configurations
+ \c
+ select name, setting from pg_settings where name = 'log_connections';
+       name       | setting 
+ -----------------+---------
+  log_connections | on
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'max_connections';
+       name       | setting 
+ -----------------+---------
+  max_connections | 100
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'wal_level';
+    name    | setting 
+ -----------+---------
+  wal_level | minimal
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'authentication_timeout';
+           name          | setting 
+ ------------------------+---------
+  authentication_timeout | 10
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'vacuum_cost_delay';
+        name        | setting 
+ -------------------+---------
+  vacuum_cost_delay | 0
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'bgwriter_lru_multiplier';
+           name           | setting 
+ -------------------------+---------
+  bgwriter_lru_multiplier | 3.2
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'full_page_writes';
+        name       | setting 
+ ------------------+---------
+  full_page_writes | off
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'synchronous_commit';
+         name        | setting 
+ --------------------+---------
+  synchronous_commit | off
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'synchronous_standby_names';
+            name            |      setting       
+ ---------------------------+--------------------
+  synchronous_standby_names | standby1, standby2
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'seq_page_cost';
+      name      | setting 
+ ---------------+---------
+  seq_page_cost | 0.9
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'autovacuum_naptime';
+         name        | setting 
+ --------------------+---------
+  autovacuum_naptime | 30
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'search_path';
+     name     | setting 
+ -------------+---------
+  search_path | public
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'default_tablespace';
+         name        | setting 
+ --------------------+---------
+  default_tablespace | 
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'checkpoint_timeout';
+         name        | setting 
+ --------------------+---------
+  checkpoint_timeout | 90
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'restart_after_crash';
+         name         | setting 
+ ---------------------+---------
+  restart_after_crash | on
+ (1 row)
+ 
+ -- Reset the some of the parameters which are set in above
+ reset persistent log_connections;
+ reset persistent max_connections;
+ reset persistent authentication_timeout;
+ reset persistent synchronous_commit;
+ reset persistent restart_after_crash;
+ -- reload the new configurations.
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'log_connections';
+       name       | setting 
+ -----------------+---------
+  log_connections | on
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'max_connections';
+       name       | setting 
+ -----------------+---------
+  max_connections | 100
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'authentication_timeout';
+           name          | setting 
+ ------------------------+---------
+  authentication_timeout | 60
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'seq_page_cost';
+      name      | setting 
+ ---------------+---------
+  seq_page_cost | 0.9
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'restart_after_crash';
+         name         | setting 
+ ---------------------+---------
+  restart_after_crash | on
+ (1 row)
+ 
+ -- reconnect to see the new configurations
+ \c
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  1min
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- set the parameters again which are reset above.
+ set persistent log_connections To yes;
+ set persistent max_connections = 50;
+ set persistent authentication_timeout = 20;
+ set persistent synchronous_commit To off;
+ set persistent restart_after_crash To yes;
+ -- reload the new configurations.
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  20s
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- reconnect to see the new configurations
+ \c
+ show log_connections;
+  log_connections 
+ -----------------
+  on
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  20s
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- set a configuration param inside a function
+ show enable_hashagg;
+  enable_hashagg 
+ ----------------
+  on
+ (1 row)
+ 
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ set persistent enable_hashagg=off;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ select persistent_func();
+  persistent_func 
+ -----------------
+                1
+ (1 row)
+ 
+ show enable_hashagg;
+  enable_hashagg 
+ ----------------
+  on
+ (1 row)
+ 
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show enable_hashagg;
+  enable_hashagg 
+ ----------------
+  off
+ (1 row)
+ 
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ reset persistent enable_hashagg;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ select persistent_func();
+  persistent_func 
+ -----------------
+                1
+ (1 row)
+ 
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show enable_hashagg;
+  enable_hashagg 
+ ----------------
+  on
+ (1 row)
+ 
+ Drop function persistent_func();
+ -- Reset all parameters which are set at above.
+ reset persistent all;
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show log_connections;
+  log_connections 
+ -----------------
+  on
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  1min
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  1
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- Normal user tries to set
+ create user test password 'test';
+ SET SESSION AUTHORIZATION test;
+ reset persistent enable_seqscan;
+ ERROR:  must be superuser to execute SET/RESET PERSISTENT command
+ \c -
+ drop user test;
+ -- In a transaction block tries to set
+ start transaction;
+ set persistent enable_hashagg=off;
+ ERROR:  SET/RESET PERSISTENT command cannot run inside a transaction block
+ commit;
+ start transaction;
+ reset persistent enable_hashagg;
+ ERROR:  SET/RESET PERSISTENT command cannot run inside a transaction block
+ commit;
+ -- Reset all parameters which are set at above.
+ reset persistent all;
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
*** a/src/test/regress/parallel_schedule
--- b/src/test/regress/parallel_schedule
***************
*** 108,111 **** test: select_views portals_p2 foreign_key cluster dependency guc bitmapops combo
  test: plancache limit plpgsql copy2 temp domain rangefuncs prepare without_oid conversion truncate alter_table sequence polymorphism rowtypes returning largeobject with xml
  
  # run stats by itself because its delay may be insufficient under heavy load
! test: stats
--- 108,114 ----
  test: plancache limit plpgsql copy2 temp domain rangefuncs prepare without_oid conversion truncate alter_table sequence polymorphism rowtypes returning largeobject with xml
  
  # run stats by itself because its delay may be insufficient under heavy load
! test: stats 
! 
! # run persistent by itself because it modifies the configuration parameters
! test: persistent
*** a/src/test/regress/serial_schedule
--- b/src/test/regress/serial_schedule
***************
*** 134,136 **** test: largeobject
--- 134,137 ----
  test: with
  test: xml
  test: stats
+ test: persistent
*** /dev/null
--- b/src/test/regress/sql/persistent.sql
***************
*** 0 ****
--- 1,428 ----
+ -- parameter which cannot be set after connection start.
+ set persistent log_connections=on;
+ 
+ -- parameter can only be set at during server start.
+ set persistent max_connections To 10;
+ set persistent wal_level = hot_standby;
+ 
+ -- parameter can set by the backend
+ set persistent authentication_timeout = 10;
+ set persistent vacuum_cost_delay To 200;
+ set persistent bgwriter_lru_multiplier = 3.2;
+ set persistent full_page_writes = off;
+ set persistent synchronous_commit To off;
+ set persistent synchronous_standby_names = 'standby1, standby2';
+ set persistent seq_page_cost = 0.9;
+ set persistent autovacuum_naptime To 30;
+ set persistent search_path = 'public';
+ set persistent default_tablespace = '';
+ set persistent checkpoint_timeout = 1;
+ set persistent checkpoint_timeout = 3700;
+ set persistent checkpoint_timeout = 90;
+ set persistent restart_after_crash TO on;
+ 
+ 
+ show log_connections;
+ 
+ show max_connections;
+ show wal_level;
+ 
+ show authentication_timeout;
+ show vacuum_cost_delay;
+ show bgwriter_lru_multiplier;
+ show full_page_writes;
+ show synchronous_commit;
+ show synchronous_standby_names;
+ show seq_page_cost;
+ show autovacuum_naptime;
+ show search_path;
+ show default_tablespace;
+ show checkpoint_timeout;
+ show restart_after_crash;
+           
+ -- reload the new configurations.
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show log_connections;
+ 
+ show max_connections;
+ show wal_level;
+ 
+ show authentication_timeout;
+ show vacuum_cost_delay;
+ show bgwriter_lru_multiplier;
+ show full_page_writes;
+ show synchronous_commit;
+ show synchronous_standby_names;
+ show seq_page_cost;
+ show autovacuum_naptime;
+ show search_path;
+ show default_tablespace;
+ show checkpoint_timeout;
+ show restart_after_crash;
+ 
+ 
+ -- reconnect to see the new configurations
+ \c
+ 
+ select name, setting from pg_settings where name = 'log_connections';
+ 
+ select name, setting from pg_settings where name = 'max_connections';
+ select name, setting from pg_settings where name = 'wal_level';
+ 
+ select name, setting from pg_settings where name = 'authentication_timeout';
+ select name, setting from pg_settings where name = 'vacuum_cost_delay';
+ select name, setting from pg_settings where name = 'bgwriter_lru_multiplier';
+ select name, setting from pg_settings where name = 'full_page_writes';
+ select name, setting from pg_settings where name = 'synchronous_commit';
+ select name, setting from pg_settings where name = 'synchronous_standby_names';
+ select name, setting from pg_settings where name = 'seq_page_cost';
+ select name, setting from pg_settings where name = 'autovacuum_naptime';
+ select name, setting from pg_settings where name = 'search_path';
+ select name, setting from pg_settings where name = 'default_tablespace';
+ select name, setting from pg_settings where name = 'checkpoint_timeout';
+ select name, setting from pg_settings where name = 'restart_after_crash';
+ 
+ -- Reset the some of the parameters which are set in above
+ set persistent log_connections = default;
+ 
+ set persistent max_connections To default;
+ 
+ set persistent authentication_timeout To default;
+ set persistent synchronous_commit = default;
+ set persistent restart_after_crash To default;
+ 
+ -- reload the new configurations.
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ select name, setting from pg_settings where name = 'log_connections';
+ select name, setting from pg_settings where name = 'max_connections';
+ select name, setting from pg_settings where name = 'authentication_timeout';
+ select name, setting from pg_settings where name = 'seq_page_cost';
+ select name, setting from pg_settings where name = 'restart_after_crash';
+ 
+ -- reconnect to see the new configurations
+ \c
+ 
+ show log_connections;
+ show max_connections;
+ show authentication_timeout;
+ show seq_page_cost;
+ show restart_after_crash;
+ 
+ -- set the parameters again which are reset above.
+ set persistent log_connections To yes;
+ 
+ set persistent max_connections = 50;
+ 
+ set persistent authentication_timeout = 20;
+ set persistent synchronous_commit To off;
+ set persistent restart_after_crash To yes;
+ 
+ -- reload the new configurations.
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show log_connections;
+ show max_connections;
+ show authentication_timeout;
+ show seq_page_cost;
+ show restart_after_crash;
+ 
+ -- reconnect to see the new configurations
+ \c
+ show log_connections;
+ show max_connections;
+ show authentication_timeout;
+ show seq_page_cost;
+ show restart_after_crash;
+ 
+ -- set a configuration param inside a function
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ set persistent enable_hashagg=off;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ 
+ select persistent_func();
+ 
+ show enable_hashagg;
+ 
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show enable_hashagg;
+ 
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ set persistent enable_hashagg=default;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ 
+ select persistent_func();
+ 
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show enable_hashagg;
+ 
+ Drop function persistent_func();
+ 
+ -- Reset all parameters which are set at above.
+ set persistent log_connections To default;
+ 
+ set persistent max_connections = default;
+ set persistent wal_level To default;
+ 
+ set persistent authentication_timeout To default;
+ set persistent vacuum_cost_delay = default;
+ set persistent bgwriter_lru_multiplier To default;
+ set persistent full_page_writes To default;
+ set persistent synchronous_commit = default;
+ set persistent synchronous_standby_names To default;
+ set persistent seq_page_cost To default;
+ set persistent autovacuum_naptime = default;
+ set persistent search_path To default;
+ set persistent default_tablespace To default;
+ set persistent checkpoint_timeout To default;
+ set persistent restart_after_crash = default;
+ 
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ 
+ -- Normal user tries to set
+ create user test password 'test';
+ SET SESSION AUTHORIZATION test;
+ set persistent enable_seqscan=off;
+ \c -
+ drop user test;
+ 
+ -- In a transaction block tries to set
+ start transaction;
+ set persistent enable_hashagg=off;
+ commit;
+ 
+ start transaction;
+ set persistent enable_hashagg=default;
+ commit;
+ 
+ 
+ 
+ -- parameter which cannot be set after connection start.
+ set persistent log_connections=on;
+ 
+ -- parameter can only be set at during server start.
+ set persistent max_connections To 10;
+ set persistent wal_level = hot_standby;
+ 
+ -- parameter can set by the backend
+ set persistent authentication_timeout = 10;
+ set persistent vacuum_cost_delay To 200;
+ set persistent bgwriter_lru_multiplier = 3.2;
+ set persistent full_page_writes = off;
+ set persistent synchronous_commit To off;
+ set persistent synchronous_standby_names = 'standby1, standby2';
+ set persistent seq_page_cost = 0.9;
+ set persistent autovacuum_naptime To 30;
+ set persistent search_path = 'public';
+ set persistent default_tablespace = '';
+ set persistent checkpoint_timeout = 1;
+ set persistent checkpoint_timeout = 3700;
+ set persistent checkpoint_timeout = 90;
+ set persistent restart_after_crash TO on;
+ 
+ 
+ show log_connections;
+ 
+ show max_connections;
+ show wal_level;
+ 
+ show authentication_timeout;
+ show vacuum_cost_delay;
+ show bgwriter_lru_multiplier;
+ show full_page_writes;
+ show synchronous_commit;
+ show synchronous_standby_names;
+ show seq_page_cost;
+ show autovacuum_naptime;
+ show search_path;
+ show default_tablespace;
+ show checkpoint_timeout;
+ show restart_after_crash;
+           
+ -- reload the new configurations.
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show log_connections;
+ 
+ show max_connections;
+ show wal_level;
+ 
+ show authentication_timeout;
+ show vacuum_cost_delay;
+ show bgwriter_lru_multiplier;
+ show full_page_writes;
+ show synchronous_commit;
+ show synchronous_standby_names;
+ show seq_page_cost;
+ show autovacuum_naptime;
+ show search_path;
+ show default_tablespace;
+ show checkpoint_timeout;
+ show restart_after_crash;
+ 
+ 
+ -- reconnect to see the new configurations
+ \c
+ 
+ select name, setting from pg_settings where name = 'log_connections';
+ 
+ select name, setting from pg_settings where name = 'max_connections';
+ select name, setting from pg_settings where name = 'wal_level';
+ 
+ select name, setting from pg_settings where name = 'authentication_timeout';
+ select name, setting from pg_settings where name = 'vacuum_cost_delay';
+ select name, setting from pg_settings where name = 'bgwriter_lru_multiplier';
+ select name, setting from pg_settings where name = 'full_page_writes';
+ select name, setting from pg_settings where name = 'synchronous_commit';
+ select name, setting from pg_settings where name = 'synchronous_standby_names';
+ select name, setting from pg_settings where name = 'seq_page_cost';
+ select name, setting from pg_settings where name = 'autovacuum_naptime';
+ select name, setting from pg_settings where name = 'search_path';
+ select name, setting from pg_settings where name = 'default_tablespace';
+ select name, setting from pg_settings where name = 'checkpoint_timeout';
+ select name, setting from pg_settings where name = 'restart_after_crash';
+ 
+ -- Reset the some of the parameters which are set in above
+ reset persistent log_connections;
+ 
+ reset persistent max_connections;
+ 
+ reset persistent authentication_timeout;
+ reset persistent synchronous_commit;
+ reset persistent restart_after_crash;
+ 
+ -- reload the new configurations.
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ select name, setting from pg_settings where name = 'log_connections';
+ select name, setting from pg_settings where name = 'max_connections';
+ select name, setting from pg_settings where name = 'authentication_timeout';
+ select name, setting from pg_settings where name = 'seq_page_cost';
+ select name, setting from pg_settings where name = 'restart_after_crash';
+ 
+ -- reconnect to see the new configurations
+ \c
+ 
+ show log_connections;
+ show max_connections;
+ show authentication_timeout;
+ show seq_page_cost;
+ show restart_after_crash;
+ 
+ -- set the parameters again which are reset above.
+ set persistent log_connections To yes;
+ 
+ set persistent max_connections = 50;
+ 
+ set persistent authentication_timeout = 20;
+ set persistent synchronous_commit To off;
+ set persistent restart_after_crash To yes;
+ 
+ -- reload the new configurations.
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show log_connections;
+ show max_connections;
+ show authentication_timeout;
+ show seq_page_cost;
+ show restart_after_crash;
+ 
+ -- reconnect to see the new configurations
+ \c
+ show log_connections;
+ show max_connections;
+ show authentication_timeout;
+ show seq_page_cost;
+ show restart_after_crash;
+ 
+ -- set a configuration param inside a function
+ show enable_hashagg;
+ 
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ set persistent enable_hashagg=off;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ 
+ select persistent_func();
+ 
+ show enable_hashagg;
+ 
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show enable_hashagg;
+ 
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ reset persistent enable_hashagg;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ 
+ select persistent_func();
+ 
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show enable_hashagg;
+ 
+ Drop function persistent_func();
+ 
+ -- Reset all parameters which are set at above.
+ reset persistent all;
+ 
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show log_connections;
+ show max_connections;
+ show authentication_timeout;
+ show seq_page_cost;
+ show restart_after_crash;
+ 
+ -- Normal user tries to set
+ create user test password 'test';
+ SET SESSION AUTHORIZATION test;
+ reset persistent enable_seqscan;
+ \c -
+ drop user test;
+ 
+ -- In a transaction block tries to set
+ start transaction;
+ set persistent enable_hashagg=off;
+ commit;
+ 
+ start transaction;
+ reset persistent enable_hashagg;
+ commit;
+ 
+ -- Reset all parameters which are set at above.
+ reset persistent all;
+ 
+ select pg_reload_conf();
+ select pg_sleep(1);

*** a/doc/src/sgml/ref/set.sgml
--- b/doc/src/sgml/ref/set.sgml
***************
*** 21,28 **** PostgreSQL documentation
  
   <refsynopsisdiv>
  <synopsis>
! SET [ SESSION | LOCAL ] <replaceable class="PARAMETER">configuration_parameter</replaceable> { TO | = } { <replaceable class="PARAMETER">value</replaceable> | '<replaceable class="PARAMETER">value</replaceable>' | DEFAULT }
! SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</replaceable> | LOCAL | DEFAULT }
  </synopsis>
   </refsynopsisdiv>
  
--- 21,28 ----
  
   <refsynopsisdiv>
  <synopsis>
! SET [ SESSION | LOCAL | PERSISTENT ] <replaceable class="PARAMETER">configuration_parameter</replaceable> { TO | = } { <replaceable class="PARAMETER">value</replaceable> | '<replaceable class="PARAMETER">value</replaceable>' | DEFAULT }
! SET [ SESSION | LOCAL | PERSISTENT ] TIME ZONE { <replaceable class="PARAMETER">timezone</replaceable> | LOCAL | DEFAULT }
  </synopsis>
   </refsynopsisdiv>
  
***************
*** 50,55 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
--- 50,64 ----
    </para>
  
    <para>
+    The <command>SET PERSISTENT</command> write the configuration parameter values to
+    <filename>postgresql.auto.conf</filename> file. with <literal>DEFAULT</literal> write the 
+    configuration parameter values to default value in <filename>postgresql.auto.conf</filename> file.
+    For deleting configuration entry in <filename>postgresql.auto.conf</filename> file use the 
+    <command>RESET PERSISTENT</command>. The values will be effective after reload of 
+    server configuration (SIGHUP) or server startup.  
+   </para>
+   
+   <para>
     The effects of <command>SET LOCAL</command> last only till the end of
     the current transaction, whether committed or not.  A special case is
     <command>SET</command> followed by <command>SET LOCAL</command> within
***************
*** 86,92 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
      <application>PL/pgSQL</application> exception block.  This behavior
      has been changed because it was deemed unintuitive.
     </para>
!   </note>
   </refsect1>
  
   <refsect1>
--- 95,101 ----
      <application>PL/pgSQL</application> exception block.  This behavior
      has been changed because it was deemed unintuitive.
     </para>
!    </note>
   </refsect1>
  
   <refsect1>
***************
*** 98,105 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
      <listitem>
       <para>
        Specifies that the command takes effect for the current session.
!       (This is the default if neither <literal>SESSION</> nor
!       <literal>LOCAL</> appears.)
       </para>
      </listitem>
     </varlistentry>
--- 107,114 ----
      <listitem>
       <para>
        Specifies that the command takes effect for the current session.
!       (This is the default option, if any of <literal>SESSION</>, 
!       <literal>LOCAL</> or <literal>PERSISTENT</> are not provided.)
       </para>
      </listitem>
     </varlistentry>
***************
*** 119,124 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
--- 128,144 ----
     </varlistentry>
  
     <varlistentry>
+     <term><literal>PERSISTENT</></term>
+     <listitem>
+      <para>
+       Writes updated configuration paramters in <filename>postgresql.auto.conf</filename>.
+       These configuration parameters takes effect after reload of configuration
+       file (SIGHUP) or in next server start based on type of configuration parameter modified.
+      </para>
+     </listitem>
+    </varlistentry>
+ 
+    <varlistentry>
      <term><replaceable class="PARAMETER">configuration_parameter</replaceable></term>
      <listitem>
       <para>
***************
*** 154,160 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
      <varlistentry>
       <term><literal>SCHEMA</literal></term>
       <listitem>
!       <para><literal>SET SCHEMA '<replaceable>value</>'</> is an alias for
         <literal>SET search_path TO <replaceable>value</></>.  Only one
         schema can be specified using this syntax.
        </para>
--- 174,180 ----
      <varlistentry>
       <term><literal>SCHEMA</literal></term>
       <listitem>
!       <para><literal>SET [ PERSISTENT ] SCHEMA '<replaceable>value</>'</> is an alias for
         <literal>SET search_path TO <replaceable>value</></>.  Only one
         schema can be specified using this syntax.
        </para>
***************
*** 164,170 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
      <varlistentry>
       <term><literal>NAMES</literal></term>
       <listitem>
!       <para><literal>SET NAMES <replaceable>value</></> is an alias for
         <literal>SET client_encoding TO <replaceable>value</></>.
        </para>
       </listitem>
--- 184,190 ----
      <varlistentry>
       <term><literal>NAMES</literal></term>
       <listitem>
!       <para><literal>SET [ PERSISTENT ] NAMES <replaceable>value</></> is an alias for
         <literal>SET client_encoding TO <replaceable>value</></>.
        </para>
       </listitem>
***************
*** 192,198 **** SELECT setseed(<replaceable>value</replaceable>);
      <varlistentry>
       <term><literal>TIME ZONE</literal></term>
       <listitem>
!       <para><literal>SET TIME ZONE <replaceable>value</></> is an alias
         for <literal>SET timezone TO <replaceable>value</></>.  The
         syntax <literal>SET TIME ZONE</literal> allows special syntax
         for the time zone specification.  Here are examples of valid
--- 212,218 ----
      <varlistentry>
       <term><literal>TIME ZONE</literal></term>
       <listitem>
!       <para><literal>SET [ PERSISTENT ] TIME ZONE <replaceable>value</></> is an alias
         for <literal>SET timezone TO <replaceable>value</></>.  The
         syntax <literal>SET TIME ZONE</literal> allows special syntax
         for the time zone specification.  Here are examples of valid
*** a/src/backend/nodes/copyfuncs.c
--- b/src/backend/nodes/copyfuncs.c
***************
*** 3264,3269 **** _copyVariableSetStmt(const VariableSetStmt *from)
--- 3264,3270 ----
  	COPY_STRING_FIELD(name);
  	COPY_NODE_FIELD(args);
  	COPY_SCALAR_FIELD(is_local);
+ 	COPY_SCALAR_FIELD(is_persistent);
  
  	return newnode;
  }
*** a/src/backend/nodes/equalfuncs.c
--- b/src/backend/nodes/equalfuncs.c
***************
*** 1555,1560 **** _equalVariableSetStmt(const VariableSetStmt *a, const VariableSetStmt *b)
--- 1555,1561 ----
  	COMPARE_STRING_FIELD(name);
  	COMPARE_NODE_FIELD(args);
  	COMPARE_SCALAR_FIELD(is_local);
+ 	COMPARE_SCALAR_FIELD(is_persistent);
  
  	return true;
  }
*** a/src/backend/parser/gram.y
--- b/src/backend/parser/gram.y
***************
*** 394,400 **** static void processCASbits(int cas_bits, int location, const char *constrType,
  
  %type <istmt>	insert_rest
  
! %type <vsetstmt> set_rest set_rest_more SetResetClause FunctionSetResetClause
  
  %type <node>	TableElement TypedTableElement ConstraintElem TableFuncElement
  				ForeignTableElement
--- 394,400 ----
  
  %type <istmt>	insert_rest
  
! %type <vsetstmt> set_rest set_rest_common set_rest_more SetResetClause FunctionSetResetClause
  
  %type <node>	TableElement TypedTableElement ConstraintElem TableFuncElement
  				ForeignTableElement
***************
*** 564,571 **** static void processCASbits(int cas_bits, int location, const char *constrType,
  	OBJECT_P OF OFF OFFSET OIDS ON ONLY OPERATOR OPTION OPTIONS OR
  	ORDER OUT_P OUTER_P OVER OVERLAPS OVERLAY OWNED OWNER
  
! 	PARSER PARTIAL PARTITION PASSING PASSWORD PLACING PLANS POSITION
! 	PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY
  	PRIOR PRIVILEGES PROCEDURAL PROCEDURE
  
  	QUOTE
--- 564,571 ----
  	OBJECT_P OF OFF OFFSET OIDS ON ONLY OPERATOR OPTION OPTIONS OR
  	ORDER OUT_P OUTER_P OVER OVERLAPS OVERLAY OWNED OWNER
  
! 	PARSER PARTIAL PARTITION PASSING PASSWORD PERSISTENT PLACING PLANS
! 	POSITION PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY
  	PRIOR PRIVILEGES PROCEDURAL PROCEDURE
  
  	QUOTE
***************
*** 1293,1298 **** VariableSetStmt:
--- 1293,1304 ----
  					n->is_local = false;
  					$$ = (Node *) n;
  				}
+ 			| SET PERSISTENT set_rest_common
+ 				{
+ 					VariableSetStmt *n = $3;
+ 					n->is_persistent = true;
+ 					$$ = (Node *) n;
+ 				}
  		;
  
  set_rest:
***************
*** 1315,1321 **** set_rest:
  			| set_rest_more
  			;
  
! set_rest_more:	/* Generic SET syntaxes: */
  			var_name TO var_list
  				{
  					VariableSetStmt *n = makeNode(VariableSetStmt);
--- 1321,1327 ----
  			| set_rest_more
  			;
  
! set_rest_common:	/* common SET syntaxes: */
  			var_name TO var_list
  				{
  					VariableSetStmt *n = makeNode(VariableSetStmt);
***************
*** 1346,1358 **** set_rest_more:	/* Generic SET syntaxes: */
  					n->name = $1;
  					$$ = n;
  				}
- 			| var_name FROM CURRENT_P
- 				{
- 					VariableSetStmt *n = makeNode(VariableSetStmt);
- 					n->kind = VAR_SET_CURRENT;
- 					n->name = $1;
- 					$$ = n;
- 				}
  			/* Special syntaxes mandated by SQL standard: */
  			| TIME ZONE zone_value
  				{
--- 1352,1357 ----
***************
*** 1365,1378 **** set_rest_more:	/* Generic SET syntaxes: */
  						n->kind = VAR_SET_DEFAULT;
  					$$ = n;
  				}
- 			| CATALOG_P Sconst
- 				{
- 					ereport(ERROR,
- 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
- 							 errmsg("current database cannot be changed"),
- 							 parser_errposition(@2)));
- 					$$ = NULL; /*not reached*/
- 				}
  			| SCHEMA Sconst
  				{
  					VariableSetStmt *n = makeNode(VariableSetStmt);
--- 1364,1369 ----
***************
*** 1381,1386 **** set_rest_more:	/* Generic SET syntaxes: */
--- 1372,1404 ----
  					n->args = list_make1(makeStringConst($2, @2));
  					$$ = n;
  				}
+ 			| XML_P OPTION document_or_content
+ 				{
+ 					VariableSetStmt *n = makeNode(VariableSetStmt);
+ 					n->kind = VAR_SET_VALUE;
+ 					n->name = "xmloption";
+ 					n->args = list_make1(makeStringConst($3 == XMLOPTION_DOCUMENT ? "DOCUMENT" : "CONTENT", @3));
+ 					$$ = n;
+ 				}
+ 			;
+ 
+ set_rest_more:	/* Generic SET syntaxes: */
+ 			set_rest_common
+ 			| var_name FROM CURRENT_P
+ 				{
+ 					VariableSetStmt *n = makeNode(VariableSetStmt);
+ 					n->kind = VAR_SET_CURRENT;
+ 					n->name = $1;
+ 					$$ = n;
+ 				}
+ 			| CATALOG_P Sconst
+ 				{
+ 					ereport(ERROR,
+ 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ 							 errmsg("current database cannot be changed"),
+ 							 parser_errposition(@2)));
+ 					$$ = NULL; /*not reached*/
+ 				}
  			| NAMES opt_encoding
  				{
  					VariableSetStmt *n = makeNode(VariableSetStmt);
***************
*** 1415,1428 **** set_rest_more:	/* Generic SET syntaxes: */
  					n->name = "session_authorization";
  					$$ = n;
  				}
- 			| XML_P OPTION document_or_content
- 				{
- 					VariableSetStmt *n = makeNode(VariableSetStmt);
- 					n->kind = VAR_SET_VALUE;
- 					n->name = "xmloption";
- 					n->args = list_make1(makeStringConst($3 == XMLOPTION_DOCUMENT ? "DOCUMENT" : "CONTENT", @3));
- 					$$ = n;
- 				}
  			/* Special syntaxes invented by PostgreSQL: */
  			| TRANSACTION SNAPSHOT Sconst
  				{
--- 1433,1438 ----
***************
*** 12590,12595 **** unreserved_keyword:
--- 12600,12606 ----
  			| PARTITION
  			| PASSING
  			| PASSWORD
+ 			| PERSISTENT
  			| PLANS
  			| PRECEDING
  			| PREPARE
*** a/src/backend/postmaster/postmaster.c
--- b/src/backend/postmaster/postmaster.c
***************
*** 2556,2561 **** reaper(SIGNAL_ARGS)
--- 2556,2573 ----
  				continue;
  			}
  
+ 			/* Delete the postgresql.auto.conf.lock file if exists */
+ 			{
+ 				char		LockFileName[MAXPGPATH];
+ 
+ 				strlcpy(LockFileName, ConfigFileName, sizeof(LockFileName));
+ 				get_parent_directory(LockFileName);
+ 				join_path_components(LockFileName, LockFileName, AutoConfigLockFilename);
+ 				canonicalize_path(LockFileName);
+ 
+ 				unlink(LockFileName);
+ 			}
+ 
  			/*
  			 * Startup succeeded, commence normal operations
  			 */
*** a/src/backend/replication/basebackup.c
--- b/src/backend/replication/basebackup.c
***************
*** 581,586 **** sendDir(char *path, int basepathlen, bool sizeonly)
--- 581,592 ----
  					strlen(PG_TEMP_FILE_PREFIX)) == 0)
  			continue;
  
+ 		/* skip lock files used in postgresql.auto.conf edit */
+ 		if (strncmp(de->d_name,
+ 					"postgresql.auto.conf.lock",
+ 					strlen("postgresql.auto.conf.lock")) == 0)
+ 			continue;
+ 
  		/*
  		 * If there's a backup_label file, it belongs to a backup started by
  		 * the user with pg_start_backup(). It is *not* correct for this
*** a/src/backend/utils/misc/guc-file.l
--- b/src/backend/utils/misc/guc-file.l
***************
*** 41,46 **** enum {
--- 41,47 ----
  	GUC_ERROR = 100
  };
  
+ static bool is_config_dir_parsed = false;
  static unsigned int ConfigFileLineno;
  static const char *GUC_flex_fatal_errmsg;
  static sigjmp_buf *GUC_flex_fatal_jmp;
***************
*** 137,142 **** ProcessConfigFile(GucContext context)
--- 138,145 ----
  	/* Parse the file into a list of option names and values */
  	head = tail = NULL;
  
+ 	is_config_dir_parsed = false;
+ 
  	if (!ParseConfigFile(ConfigFileName, NULL, true, 0, elevel, &head, &tail))
  	{
  		/* Syntax error(s) detected in the file, so bail out */
***************
*** 144,149 **** ProcessConfigFile(GucContext context)
--- 147,159 ----
  		goto cleanup_list;
  	}
  
+ 	if (!is_config_dir_parsed)
+ 	{
+ 		ereport(WARNING,
+ 				(errmsg("Default \"config_dir\" is not present in postgresql.conf."
+ 						"Any configuration value changed with SET PERSISTENT command will not be effective.")));
+ 	}
+ 
  	/*
  	 * Mark all extant GUC variables as not present in the config file.
  	 * We need this so that we can tell below which ones have been removed
***************
*** 367,373 **** ProcessConfigFile(GucContext context)
   * path, return an absolute one.  We consider the location to be relative to
   * the directory holding the calling file.
   */
! static char *
  AbsoluteConfigLocation(const char *location, const char *calling_file)
  {
  	char		abs_path[MAXPGPATH];
--- 377,383 ----
   * path, return an absolute one.  We consider the location to be relative to
   * the directory holding the calling file.
   */
! char *
  AbsoluteConfigLocation(const char *location, const char *calling_file)
  {
  	char		abs_path[MAXPGPATH];
***************
*** 411,416 **** ParseConfigFile(const char *config_file, const char *calling_file, bool strict,
--- 421,427 ----
  {
  	bool		OK = true;
  	FILE	   *fp;
+ 	char 		*ConfigAutoFileName;
  
  	/*
  	 * Reject too-deep include nesting depth.  This is just a safety check
***************
*** 427,432 **** ParseConfigFile(const char *config_file, const char *calling_file, bool strict,
--- 438,449 ----
  	}
  
  	config_file = AbsoluteConfigLocation(config_file,calling_file);
+ 
+ 	/* Checking for the postgresql.auto.conf file is parsed or not */
+ 	ConfigAutoFileName = AbsoluteConfigLocation(AutoConfigFileName, ConfigFileName);
+ 	if (depth == 1 && strcmp(ConfigAutoFileName, config_file) == 0)
+ 		is_config_dir_parsed = true;
+ 
  	fp = AllocateFile(config_file, "r");
  	if (!fp)
  	{
***************
*** 533,538 **** ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
--- 550,556 ----
  	{
  		char	   *opt_name = NULL;
  		char	   *opt_value = NULL;
+ 		bool		is_string = false;
  		ConfigVariable *item;
  
  		if (token == GUC_EOL)	/* empty or comment line */
***************
*** 556,562 **** ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
--- 574,583 ----
  			token != GUC_UNQUOTED_STRING)
  			goto parse_error;
  		if (token == GUC_STRING)	/* strip quotes and escapes */
+ 		{
  			opt_value = GUC_scanstr(yytext);
+ 			is_string = true;
+ 		}
  		else
  			opt_value = pstrdup(yytext);
  
***************
*** 620,625 **** ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
--- 641,647 ----
  			item = palloc(sizeof *item);
  			item->name = opt_name;
  			item->value = opt_value;
+ 			item->is_quoted = is_string;
  			item->filename = pstrdup(config_file);
  			item->sourceline = ConfigFileLineno-1;
  			item->next = NULL;
*** a/src/backend/utils/misc/guc.c
--- b/src/backend/utils/misc/guc.c
***************
*** 3361,3366 **** static void ShowAllGUCConfig(DestReceiver *dest);
--- 3361,3371 ----
  static char *_ShowOption(struct config_generic * record, bool use_units);
  static bool validate_option_array_item(const char *name, const char *value,
  						   bool skipIfNoPermissions);
+ static int	create_conf_lock_file(const char *LockFileName);
+ static void write_auto_conf_file(int fd, ConfigVariable **head_p);
+ static void replace_auto_config_value(ConfigVariable **head_p, ConfigVariable **tail_p,
+ 				 char *config_file, char *name, char *value, bool is_quoted);
+ static void set_config_file(VariableSetStmt *setstmt);
  
  
  /*
***************
*** 4133,4138 **** SelectConfigFiles(const char *userDoption, const char *progname)
--- 4138,4152 ----
  		return false;
  	}
  
+ 	/* Remove postgresql.auto.conf.lock file make be left over from last crash */
+ 	if (!IsUnderPostmaster)
+ 	{
+ 		char	   *LockFileName;
+ 
+ 		LockFileName = AbsoluteConfigLocation(AutoConfigLockFilename, ConfigFileName);
+ 		unlink(LockFileName);
+ 	}
+ 
  	ProcessConfigFile(PGC_POSTMASTER);
  
  	/*
***************
*** 5107,5112 **** config_enum_get_options(struct config_enum * record, const char *prefix,
--- 5121,5305 ----
  	return retstr.data;
  }
  
+ /*
+  * Validates configuration parameter and value, incase of source is default
+  * returns the default value in string format.
+  */
+ struct config_generic *
+ validate_conf_option(const char *name, char *value)
+ {
+ 	struct config_generic *record;
+ 
+ 	record = find_option(name, true, LOG);
+ 	if (record == NULL)
+ 	{
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_UNDEFINED_OBJECT),
+ 			   errmsg("unrecognized configuration parameter \"%s\"", name)));
+ 	}
+ 
+ 	if (record->context == PGC_INTERNAL)
+ 	{
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
+ 				 errmsg("parameter \"%s\" cannot be changed",
+ 						name)));
+ 	}
+ 
+ 	/*
+ 	 * Evaluate value and set variable.
+ 	 */
+ 	switch (record->vartype)
+ 	{
+ 
+ 		case PGC_BOOL:
+ 			{
+ 				struct config_bool *conf = (struct config_bool *) record;
+ 				bool		newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					if (!parse_bool(value, &newval))
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						  errmsg("parameter \"%s\" requires a Boolean value",
+ 								 name)));
+ 					}
+ 					if (!call_bool_check_hook(conf, &newval, &newextra,
+ 											  PGC_S_FILE, LOG))
+ 						return NULL;
+ 				}
+ 			}
+ 			break;
+ 		case PGC_INT:
+ 			{
+ 				struct config_int *conf = (struct config_int *) record;
+ 				int			newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					const char *hintmsg;
+ 
+ 					if (!parse_int(value, &newval, conf->gen.flags, &hintmsg))
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						 errmsg("invalid value for parameter \"%s\": \"%s\"",
+ 								name, value),
+ 								 hintmsg ? errhint("%s", _(hintmsg)) : 0));
+ 					}
+ 					if (newval < conf->min || newval > conf->max)
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 								 errmsg("%d is outside the valid range for parameter \"%s\" (%d .. %d)",
+ 										newval, name, conf->min, conf->max)));
+ 					}
+ 					if (!call_int_check_hook(conf, &newval, &newextra,
+ 											 PGC_S_FILE, LOG))
+ 						return NULL;
+ 				}
+ 			}
+ 			break;
+ 		case PGC_REAL:
+ 			{
+ 				struct config_real *conf = (struct config_real *) record;
+ 				double		newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					if (!parse_real(value, &newval))
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						  errmsg("parameter \"%s\" requires a numeric value",
+ 								 name)));
+ 					}
+ 					if (newval < conf->min || newval > conf->max)
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 								 errmsg("%g is outside the valid range for parameter \"%s\" (%g .. %g)",
+ 										newval, name, conf->min, conf->max)));
+ 					}
+ 					if (!call_real_check_hook(conf, &newval, &newextra,
+ 											  PGC_S_FILE, LOG))
+ 						return NULL;
+ 				}
+ 			}
+ 			break;
+ 		case PGC_STRING:
+ 			{
+ 				struct config_string *conf = (struct config_string *) record;
+ 				char	   *newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					/*
+ 					 * The value passed by the caller could be transient, so
+ 					 * we always strdup it.
+ 					 */
+ 					newval = guc_strdup(LOG, value);
+ 					if (newval == NULL)
+ 						return NULL;
+ 
+ 					/*
+ 					 * The only built-in "parsing" check we have is to apply
+ 					 * truncation if GUC_IS_NAME.
+ 					 */
+ 					if (conf->gen.flags & GUC_IS_NAME)
+ 						truncate_identifier(newval, strlen(newval), true);
+ 
+ 					if (!call_string_check_hook(conf, &newval, &newextra,
+ 												PGC_S_FILE, LOG))
+ 					{
+ 						free(newval);
+ 						return NULL;
+ 					}
+ 				}
+ 			}
+ 			break;
+ 		case PGC_ENUM:
+ 			{
+ 				struct config_enum *conf = (struct config_enum *) record;
+ 				int			newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					if (!config_enum_lookup_by_name(conf, value, &newval))
+ 					{
+ 						char	   *hintmsg;
+ 
+ 						hintmsg = config_enum_get_options(conf,
+ 														"Available values: ",
+ 														  ".", ", ");
+ 
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						 errmsg("invalid value for parameter \"%s\": \"%s\"",
+ 								name, value),
+ 								 hintmsg ? errhint("%s", _(hintmsg)) : 0));
+ 
+ 						if (hintmsg)
+ 							pfree(hintmsg);
+ 						return 0;
+ 					}
+ 					if (!call_enum_check_hook(conf, &newval, &newextra,
+ 											  PGC_S_FILE, LOG))
+ 						return 0;
+ 				}
+ 			}
+ 	}
+ 
+ 	return record;
+ }
+ 
  
  /*
   * Sets option `name' to given value.
***************
*** 5910,5915 **** set_config_sourcefile(const char *name, char *sourcefile, int sourceline)
--- 6103,6405 ----
  }
  
  /*
+  * Creates auto conf lock file used for protecting parallel modification of
+  * postgresql.auto.conf file.
+  */
+ static int
+ create_conf_lock_file(const char *LockFileName)
+ {
+ 	int			fd;
+ 	int			ntries;
+ 
+ 	/*
+ 	 * We need a loop here because of race conditions. Retry for 100 times.
+ 	 */
+ 	for (ntries = 0;; ntries++)
+ 	{
+ 		fd = open(LockFileName, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
+ 		if (fd >= 0)
+ 			break;
+ 
+ 		/*
+ 		 * Couldn't create the lock file. Probably it already exists. If so
+ 		 * wait for some time
+ 		 */
+ 		if ((errno != EEXIST && errno != EACCES) || ntries > 100)
+ 		{
+ 			if (errno != EEXIST)
+ 			{
+ 				ereport(ERROR,
+ 						(errcode_for_file_access(),
+ 						 errmsg("could not create lock file \"%s\": %m",
+ 								LockFileName)));
+ 			}
+ 			else
+ 			{
+ 				ereport(ERROR,
+ 						(errcode_for_file_access(),
+ 						 errmsg("could not create lock file \"%s\": %m ", LockFileName),
+ 						 errhint("May be too many concurrent edit into file happening, please wait!! and retry"
+ 								 "or .lock is file accidently left there please clean the file from config_dir")));
+ 			}
+ 		}
+ 		else
+ 		{
+ 			pg_usleep(100000);	/* in total wait for 10sec */
+ 		}
+ 	}
+ 
+ 	return fd;
+ }
+ 
+ 
+ /* Write updated configuration parameter values into postgresql.auto.conf.lock */
+ static void
+ write_auto_conf_file(int fd, ConfigVariable **head_p)
+ {
+ 	ConfigVariable *item;
+ 	StringInfoData buf;
+ 
+ 	initStringInfo(&buf);
+ 
+ 	for (item = *head_p; item != NULL; item = item->next)
+ 	{
+ 		appendStringInfoString(&buf, item->name);
+ 		appendStringInfoString(&buf, " = ");
+ 
+ 		if (true == item->is_quoted)
+ 		{
+ 			appendStringInfoString(&buf, "\'");
+ 			appendStringInfoString(&buf, item->value);
+ 			appendStringInfoString(&buf, "\'");
+ 		}
+ 		else
+ 		{
+ 			appendStringInfoString(&buf, item->value);
+ 		}
+ 
+ 		appendStringInfoString(&buf, "\n");
+ 
+ 		if (write(fd, buf.data, buf.len) < 0)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("failed to write into to \"postgresql.auto.conf.lock\" file")));
+ 		}
+ 
+ 		resetStringInfo(&buf);
+ 	}
+ 
+ 	if (pg_fsync(fd) != 0)
+ 		ereport(ERROR,
+ 				(errcode_for_file_access(),
+ 		  errmsg("could not fsync file \"postgresql.auto.conf.lock\": %m")));
+ 
+ 
+ 	pfree(buf.data);
+ 	return;
+ }
+ 
+ 
+ /*
+  * Replace the updated configuration parameter value in postgresql.auto.conf
+  * file lines. If it is new then append extra line at the end of lines.
+  */
+ static void
+ replace_auto_config_value(ConfigVariable **head_p, ConfigVariable **tail_p,
+ 						  char *config_file, char *name, char *value,
+ 						  bool is_quoted)
+ {
+ 	ConfigVariable *item,
+ 			   *prev = NULL;
+ 
+ 	if (NULL != *head_p)
+ 	{
+ 		for (item = *head_p; item != NULL; item = item->next)
+ 		{
+ 			if (strcmp(item->name, name) == 0)
+ 			{
+ 				pfree(item->value);
+ 				if (value)
+ 				{
+ 					/* update the parameter value */
+ 					item->value = pstrdup(value);
+ 				}
+ 				else
+ 				{
+ 					/* delete the configuration parameter from list */
+ 					if (*head_p == item)
+ 					{
+ 						*head_p = item->next;
+ 					}
+ 					else
+ 					{
+ 						prev->next = item->next;
+ 					}
+ 
+ 					if (*tail_p == item)
+ 					{
+ 						*tail_p = prev;
+ 					}
+ 					pfree(item->name);
+ 					pfree(item->filename);
+ 					pfree(item);
+ 				}
+ 				return;
+ 			}
+ 			prev = item;
+ 		}
+ 	}
+ 
+ 	if (NULL == value)
+ 	{
+ 		return;
+ 	}
+ 
+ 	item = palloc(sizeof *item);
+ 	item->name = pstrdup(name);
+ 	item->value = pstrdup(value);
+ 	item->is_quoted = is_quoted;
+ 	item->filename = pstrdup(config_file);
+ 	item->next = NULL;
+ 
+ 	if (*head_p == NULL)
+ 	{
+ 		item->sourceline = 1;
+ 		*head_p = item;
+ 	}
+ 	else
+ 	{
+ 		item->sourceline = (*tail_p)->sourceline + 1;
+ 		(*tail_p)->next = item;
+ 	}
+ 
+ 	*tail_p = item;
+ 
+ 	return;
+ }
+ 
+ 
+ /*
+  * Persist the configuration parameter value.
+  * Writes the value of configuration parameter in postgresql.auto.conf.lock file.
+  * .lock file is used to disallow changing of file by multiple backends.
+  * On Success, rename postgresql.auto.conf.lock to postgresql.auto.conf
+  * and On Failure, delete the postgresql.auto.conf.lock
+  */
+ static void
+ set_config_file(VariableSetStmt *setstmt)
+ {
+ 	char	   *name;
+ 	char	   *value;
+ 	int			lockfd = -1;
+ 	FILE	   *infile;
+ 	struct config_generic *record;
+ 	ConfigVariable *head_p = NULL;
+ 	ConfigVariable *tail_p = NULL;
+ 	char	   *ConfAutoFileName;
+ 	char	   *LockFileName;
+ 	struct stat st;
+ 
+ 	if (!superuser())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+ 				 (errmsg("must be superuser to execute SET/RESET PERSISTENT command"))));
+ 
+ 	if (IsTransactionBlock())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_ACTIVE_SQL_TRANSACTION),
+ 				 (errmsg("SET/RESET PERSISTENT command cannot run inside a transaction block"))));
+ 
+ 	/*
+ 	 * Validate the name and arguments [value1, value2 ... ].
+ 	 */
+ 	name = setstmt->name;
+ 
+ 	switch (setstmt->kind)
+ 	{
+ 		case VAR_SET_VALUE:
+ 			value = ExtractSetVariableArgs(setstmt);
+ 			break;
+ 
+ 		case VAR_SET_DEFAULT:
+ 			value = NULL;
+ 			break;
+ 
+ 		default:
+ 			return;
+ 	}
+ 
+ 	record = validate_conf_option(name, value);
+ 	if (!record)
+ 		ereport(ERROR,
+ 		(errmsg("invalid value for parameter \"%s\": \"%s\"", name, value)));
+ 
+ 	/* Create the postgresql.auto.conf.lock file */
+ 	ConfAutoFileName = AbsoluteConfigLocation(AutoConfigFileName, ConfigFileName);
+ 	LockFileName = AbsoluteConfigLocation(AutoConfigLockFilename, ConfigFileName);
+ 
+ 	lockfd = create_conf_lock_file(LockFileName);
+ 
+ 	PG_TRY();
+ 	{
+ 		if (stat(ConfAutoFileName, &st) != 0)
+ 		{
+ 			int			fd;
+ 
+ 			fd = open(ConfAutoFileName, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
+ 			if (fd < 0)
+ 				ereport(ERROR,
+ 						(errcode_for_file_access(),
+ 						 errmsg("creation of auto conf file failed as it was not exist\"%s\": %m",
+ 								ConfAutoFileName)));
+ 			close(fd);
+ 
+ 			ereport(NOTICE,
+ 				 (errmsg("Created auto conf file as it was not exist \"%s\"",
+ 						 ConfAutoFileName)));
+ 		}
+ 
+ 		/* open postgresql.auto.conf file */
+ 		infile = AllocateFile(ConfAutoFileName, "r");
+ 		if (infile == NULL)
+ 			ereport(ERROR,
+ 					(errmsg("failed to open \"postgresql.auto.conf\" file")));
+ 
+ 		/* Parse the postgresql.auto.conf file */
+ 		ParseConfigFp(infile, ConfAutoFileName, 0, LOG, &head_p, &tail_p);
+ 
+ 		FreeFile(infile);
+ 
+ 		/* replace with new value */
+ 		replace_auto_config_value(&head_p, &tail_p, ConfAutoFileName, name,
+ 					  value, (record->vartype == PGC_STRING) ? true : false);
+ 
+ 		/* Write the New contents to postgresql.auto.conf.lock file */
+ 		write_auto_conf_file(lockfd, &head_p);
+ 
+ 		close(lockfd);
+ 		lockfd = -1;
+ 
+ 		if (rename(LockFileName, ConfAutoFileName) < 0)
+ 			ereport(ERROR,
+ 					(errcode_for_file_access(),
+ 					 errmsg("could not rename file \"%s\" to \"%s\" : %m",
+ 							LockFileName, ConfAutoFileName)));
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		if (lockfd >= 0)
+ 			close(lockfd);
+ 
+ 		unlink(LockFileName);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 	return;
+ }
+ 
+ 
+ /*
   * Set a config option to the given value.
   *
   * See also set_config_option; this is just the wrapper to be called from
***************
*** 6180,6185 **** ExecSetVariableStmt(VariableSetStmt *stmt)
--- 6670,6681 ----
  	switch (stmt->kind)
  	{
  		case VAR_SET_VALUE:
+ 			if (stmt->is_persistent)
+ 			{
+ 				set_config_file(stmt);
+ 				break;
+ 			}
+ 			/* FALLTHROUGH */
  		case VAR_SET_CURRENT:
  			(void) set_config_option(stmt->name,
  									 ExtractSetVariableArgs(stmt),
***************
*** 6259,6264 **** ExecSetVariableStmt(VariableSetStmt *stmt)
--- 6755,6766 ----
  					 stmt->name);
  			break;
  		case VAR_SET_DEFAULT:
+ 			if (stmt->is_persistent)
+ 			{
+ 				set_config_file(stmt);
+ 				break;
+ 			}
+ 			/* FALLTHROUGH */
  		case VAR_RESET:
  			(void) set_config_option(stmt->name,
  									 NULL,
*** a/src/backend/utils/misc/postgresql.conf.sample
--- b/src/backend/utils/misc/postgresql.conf.sample
***************
*** 581,586 ****
--- 581,593 ----
  #include_if_exists = 'exists.conf'	# include file only if it exists
  #include = 'special.conf'		# include file
  
+ # This includes the default configuration directory included to support
+ # SET PERSISTENT statement.
+ #
+ # WARNNING: Any configuration parameter values specified after this line
+ #           will override the values set by SET PERSISTENT statement.
+ #include_dir = 'auto.conf.d'
+ 
  #------------------------------------------------------------------------------
  # CUSTOMIZED OPTIONS
  #------------------------------------------------------------------------------
*** a/src/bin/initdb/initdb.c
--- b/src/bin/initdb/initdb.c
***************
*** 192,198 **** const char *subdirs[] = {
  	"base",
  	"base/1",
  	"pg_tblspc",
! 	"pg_stat_tmp"
  };
  
  
--- 192,199 ----
  	"base",
  	"base/1",
  	"pg_tblspc",
! 	"pg_stat_tmp",
! 	"config_dir"
  };
  
  
***************
*** 1197,1202 **** setup_config(void)
--- 1198,1204 ----
  	char		repltok[MAXPGPATH];
  	char		path[MAXPGPATH];
  	const char *default_timezone;
+ 	FILE	   *autofile;
  
  	fputs(_("creating configuration files ... "), stdout);
  	fflush(stdout);
***************
*** 1279,1289 **** setup_config(void)
--- 1281,1314 ----
  		conflines = replace_token(conflines, "#log_timezone = 'GMT'", repltok);
  	}
  
+ 	snprintf(repltok, sizeof(repltok), "include_dir = 'config_dir'");
+ 	conflines = replace_token(conflines, "#include_dir = 'auto.conf.d'", repltok);
+ 
  	snprintf(path, sizeof(path), "%s/postgresql.conf", pg_data);
  
  	writefile(path, conflines);
  	chmod(path, S_IRUSR | S_IWUSR);
  
+ 	/* create a .auto for conf file */
+ 	sprintf(path, "%s/config_dir/postgresql.auto.conf", pg_data);
+ 	autofile = fopen(path, PG_BINARY_W);
+ 	if (autofile == NULL)
+ 	{
+ 		fprintf(stderr, _("%s: could not open file \"%s\" for writing: %s\n"),
+ 				progname, path, strerror(errno));
+ 		exit_nicely();
+ 	}
+ 
+ 	if (fclose(autofile))
+ 	{
+ 		fprintf(stderr, _("%s: could not write file \"%s\": %s\n"),
+ 				progname, path, strerror(errno));
+ 		exit_nicely();
+ 	}
+ 
+ 	chmod(path, S_IRUSR | S_IWUSR);
+ 
+ 
  	free(conflines);
  
  
*** a/src/include/nodes/parsenodes.h
--- b/src/include/nodes/parsenodes.h
***************
*** 1425,1430 **** typedef struct VariableSetStmt
--- 1425,1431 ----
  	char	   *name;			/* variable to be set */
  	List	   *args;			/* List of A_Const nodes */
  	bool		is_local;		/* SET LOCAL? */
+ 	bool		is_persistent;	/* SET PERSISTENT? */
  } VariableSetStmt;
  
  /* ----------------------
*** a/src/include/parser/kwlist.h
--- b/src/include/parser/kwlist.h
***************
*** 279,284 **** PG_KEYWORD("partial", PARTIAL, UNRESERVED_KEYWORD)
--- 279,285 ----
  PG_KEYWORD("partition", PARTITION, UNRESERVED_KEYWORD)
  PG_KEYWORD("passing", PASSING, UNRESERVED_KEYWORD)
  PG_KEYWORD("password", PASSWORD, UNRESERVED_KEYWORD)
+ PG_KEYWORD("persistent", PERSISTENT, UNRESERVED_KEYWORD)
  PG_KEYWORD("placing", PLACING, RESERVED_KEYWORD)
  PG_KEYWORD("plans", PLANS, UNRESERVED_KEYWORD)
  PG_KEYWORD("position", POSITION, COL_NAME_KEYWORD)
*** a/src/include/utils/guc.h
--- b/src/include/utils/guc.h
***************
*** 105,115 **** typedef struct ConfigVariable
--- 105,118 ----
  {
  	char	   *name;
  	char	   *value;
+ 	bool		is_quoted;
  	char	   *filename;
  	int			sourceline;
  	struct ConfigVariable *next;
  } ConfigVariable;
  
+ extern char *AbsoluteConfigLocation(const char *location,
+ 					   const char *calling_file);
  extern bool ParseConfigFile(const char *config_file, const char *calling_file,
  				bool strict, int depth, int elevel,
  				ConfigVariable **head_p, ConfigVariable **tail_p);
***************
*** 191,196 **** typedef enum
--- 194,203 ----
  
  #define GUC_NOT_WHILE_SEC_REST	0x8000	/* can't set if security restricted */
  
+ /* postgresql.auto.file name and its lock */
+ #define AutoConfigFileName "config_dir/postgresql.auto.conf"
+ #define AutoConfigLockFilename	"config_dir/postgresql.auto.conf.lock"
+ 
  /* GUC vars that are actually declared in guc.c, rather than elsewhere */
  extern bool log_duration;
  extern bool Debug_print_plan;
*** a/src/include/utils/guc_tables.h
--- b/src/include/utils/guc_tables.h
***************
*** 260,265 **** extern void build_guc_variables(void);
  extern const char *config_enum_lookup_by_value(struct config_enum * record, int val);
  extern bool config_enum_lookup_by_name(struct config_enum * record,
  						   const char *value, int *retval);
! 
  
  #endif   /* GUC_TABLES_H */
--- 260,265 ----
  extern const char *config_enum_lookup_by_value(struct config_enum * record, int val);
  extern bool config_enum_lookup_by_name(struct config_enum * record,
  						   const char *value, int *retval);
! extern struct config_generic *validate_conf_option(const char *name, char *value);
  
  #endif   /* GUC_TABLES_H */
*** /dev/null
--- b/src/test/regress/expected/persistent.out
***************
*** 0 ****
--- 1,584 ----
+ -- parameter which cannot be set after connection start.
+ set persistent log_connections=on;
+ -- parameter can only be set at during server start.
+ set persistent max_connections To 10;
+ set persistent wal_level = hot_standby;
+ -- parameter can set by the backend
+ set persistent authentication_timeout = 10;
+ set persistent vacuum_cost_delay To 200;
+ ERROR:  200 is outside the valid range for parameter "vacuum_cost_delay" (0 .. 100)
+ set persistent bgwriter_lru_multiplier = 3.2;
+ set persistent full_page_writes = off;
+ set persistent synchronous_commit To off;
+ set persistent synchronous_standby_names = 'standby1, standby2';
+ set persistent seq_page_cost = 0.9;
+ set persistent autovacuum_naptime To 30;
+ set persistent search_path = 'public';
+ set persistent default_tablespace = '';
+ set persistent checkpoint_timeout = 1;
+ ERROR:  1 is outside the valid range for parameter "checkpoint_timeout" (30 .. 3600)
+ set persistent checkpoint_timeout = 3700;
+ ERROR:  3700 is outside the valid range for parameter "checkpoint_timeout" (30 .. 3600)
+ set persistent checkpoint_timeout = 90;
+ set persistent restart_after_crash TO on;
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show wal_level;
+  wal_level 
+ -----------
+  minimal
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  1min
+ (1 row)
+ 
+ show vacuum_cost_delay;
+  vacuum_cost_delay 
+ -------------------
+  0
+ (1 row)
+ 
+ show bgwriter_lru_multiplier;
+  bgwriter_lru_multiplier 
+ -------------------------
+  2
+ (1 row)
+ 
+ show full_page_writes;
+  full_page_writes 
+ ------------------
+  on
+ (1 row)
+ 
+ show synchronous_commit;
+  synchronous_commit 
+ --------------------
+  on
+ (1 row)
+ 
+ show synchronous_standby_names;
+  synchronous_standby_names 
+ ---------------------------
+  
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  1
+ (1 row)
+ 
+ show autovacuum_naptime;
+  autovacuum_naptime 
+ --------------------
+  1min
+ (1 row)
+ 
+ show search_path;
+   search_path   
+ ----------------
+  "$user",public
+ (1 row)
+ 
+ show default_tablespace;
+  default_tablespace 
+ --------------------
+  
+ (1 row)
+ 
+ show checkpoint_timeout;
+  checkpoint_timeout 
+ --------------------
+  5min
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- reload the new configurations.
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show wal_level;
+  wal_level 
+ -----------
+  minimal
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  10s
+ (1 row)
+ 
+ show vacuum_cost_delay;
+  vacuum_cost_delay 
+ -------------------
+  0
+ (1 row)
+ 
+ show bgwriter_lru_multiplier;
+  bgwriter_lru_multiplier 
+ -------------------------
+  3.2
+ (1 row)
+ 
+ show full_page_writes;
+  full_page_writes 
+ ------------------
+  off
+ (1 row)
+ 
+ show synchronous_commit;
+  synchronous_commit 
+ --------------------
+  off
+ (1 row)
+ 
+ show synchronous_standby_names;
+  synchronous_standby_names 
+ ---------------------------
+  standby1, standby2
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show autovacuum_naptime;
+  autovacuum_naptime 
+ --------------------
+  30s
+ (1 row)
+ 
+ show search_path;
+  search_path 
+ -------------
+  public
+ (1 row)
+ 
+ show default_tablespace;
+  default_tablespace 
+ --------------------
+  
+ (1 row)
+ 
+ show checkpoint_timeout;
+  checkpoint_timeout 
+ --------------------
+  90s
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- reconnect to see the new configurations
+ \c
+ select name, setting from pg_settings where name = 'log_connections';
+       name       | setting 
+ -----------------+---------
+  log_connections | on
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'max_connections';
+       name       | setting 
+ -----------------+---------
+  max_connections | 100
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'wal_level';
+    name    | setting 
+ -----------+---------
+  wal_level | minimal
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'authentication_timeout';
+           name          | setting 
+ ------------------------+---------
+  authentication_timeout | 10
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'vacuum_cost_delay';
+        name        | setting 
+ -------------------+---------
+  vacuum_cost_delay | 0
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'bgwriter_lru_multiplier';
+           name           | setting 
+ -------------------------+---------
+  bgwriter_lru_multiplier | 3.2
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'full_page_writes';
+        name       | setting 
+ ------------------+---------
+  full_page_writes | off
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'synchronous_commit';
+         name        | setting 
+ --------------------+---------
+  synchronous_commit | off
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'synchronous_standby_names';
+            name            |      setting       
+ ---------------------------+--------------------
+  synchronous_standby_names | standby1, standby2
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'seq_page_cost';
+      name      | setting 
+ ---------------+---------
+  seq_page_cost | 0.9
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'autovacuum_naptime';
+         name        | setting 
+ --------------------+---------
+  autovacuum_naptime | 30
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'search_path';
+     name     | setting 
+ -------------+---------
+  search_path | public
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'default_tablespace';
+         name        | setting 
+ --------------------+---------
+  default_tablespace | 
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'checkpoint_timeout';
+         name        | setting 
+ --------------------+---------
+  checkpoint_timeout | 90
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'restart_after_crash';
+         name         | setting 
+ ---------------------+---------
+  restart_after_crash | on
+ (1 row)
+ 
+ -- Reset the some of the parameters which are set in above
+ set persistent log_connections = default;
+ set persistent max_connections To default;
+ set persistent authentication_timeout To default;
+ set persistent synchronous_commit = default;
+ set persistent restart_after_crash To default;
+ -- reload the new configurations.
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'log_connections';
+       name       | setting 
+ -----------------+---------
+  log_connections | on
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'max_connections';
+       name       | setting 
+ -----------------+---------
+  max_connections | 100
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'authentication_timeout';
+           name          | setting 
+ ------------------------+---------
+  authentication_timeout | 60
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'seq_page_cost';
+      name      | setting 
+ ---------------+---------
+  seq_page_cost | 0.9
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'restart_after_crash';
+         name         | setting 
+ ---------------------+---------
+  restart_after_crash | on
+ (1 row)
+ 
+ -- reconnect to see the new configurations
+ \c
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  1min
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- set the parameters again which are reset above.
+ set persistent log_connections To yes;
+ set persistent max_connections = 50;
+ set persistent authentication_timeout = 20;
+ set persistent synchronous_commit To off;
+ set persistent restart_after_crash To yes;
+ -- reload the new configurations.
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  20s
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- reconnect to see the new configurations
+ \c
+ show log_connections;
+  log_connections 
+ -----------------
+  on
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  20s
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- set a configuration param inside a function
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ set persistent enable_hashagg=off;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ select persistent_func();
+  persistent_func 
+ -----------------
+                1
+ (1 row)
+ 
+ show enable_hashagg;
+  enable_hashagg 
+ ----------------
+  on
+ (1 row)
+ 
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show enable_hashagg;
+  enable_hashagg 
+ ----------------
+  off
+ (1 row)
+ 
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ set persistent enable_hashagg=default;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ select persistent_func();
+  persistent_func 
+ -----------------
+                1
+ (1 row)
+ 
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show enable_hashagg;
+  enable_hashagg 
+ ----------------
+  on
+ (1 row)
+ 
+ Drop function persistent_func();
+ -- Reset all parameters which are set at above.
+ set persistent log_connections To default;
+ set persistent max_connections = default;
+ set persistent wal_level To default;
+ set persistent authentication_timeout To default;
+ set persistent vacuum_cost_delay = default;
+ set persistent bgwriter_lru_multiplier To default;
+ set persistent full_page_writes To default;
+ set persistent synchronous_commit = default;
+ set persistent synchronous_standby_names To default;
+ set persistent seq_page_cost To default;
+ set persistent autovacuum_naptime = default;
+ set persistent search_path To default;
+ set persistent default_tablespace To default;
+ set persistent checkpoint_timeout To default;
+ set persistent restart_after_crash = default;
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ -- Normal user tries to set
+ create user test password 'test';
+ SET SESSION AUTHORIZATION test;
+ set persistent enable_seqscan=off;
+ ERROR:  must be superuser to execute SET/RESET PERSISTENT command
+ \c -
+ drop user test;
+ -- In a transaction block tries to set
+ start transaction;
+ set persistent enable_hashagg=off;
+ ERROR:  SET/RESET PERSISTENT command cannot run inside a transaction block
+ commit;
+ start transaction;
+ set persistent enable_hashagg=default;
+ ERROR:  SET/RESET PERSISTENT command cannot run inside a transaction block
+ commit;
*** a/src/test/regress/parallel_schedule
--- b/src/test/regress/parallel_schedule
***************
*** 108,111 **** test: select_views portals_p2 foreign_key cluster dependency guc bitmapops combo
  test: plancache limit plpgsql copy2 temp domain rangefuncs prepare without_oid conversion truncate alter_table sequence polymorphism rowtypes returning largeobject with xml
  
  # run stats by itself because its delay may be insufficient under heavy load
! test: stats
--- 108,114 ----
  test: plancache limit plpgsql copy2 temp domain rangefuncs prepare without_oid conversion truncate alter_table sequence polymorphism rowtypes returning largeobject with xml
  
  # run stats by itself because its delay may be insufficient under heavy load
! test: stats 
! 
! # run persistent by itself because it modifies the configuration parameters
! test: persistent
*** a/src/test/regress/serial_schedule
--- b/src/test/regress/serial_schedule
***************
*** 135,137 **** test: largeobject
--- 135,138 ----
  test: with
  test: xml
  test: stats
+ test: persistent
*** /dev/null
--- b/src/test/regress/sql/persistent.sql
***************
*** 0 ****
--- 1,215 ----
+ -- parameter which cannot be set after connection start.
+ set persistent log_connections=on;
+ 
+ -- parameter can only be set at during server start.
+ set persistent max_connections To 10;
+ set persistent wal_level = hot_standby;
+ 
+ -- parameter can set by the backend
+ set persistent authentication_timeout = 10;
+ set persistent vacuum_cost_delay To 200;
+ set persistent bgwriter_lru_multiplier = 3.2;
+ set persistent full_page_writes = off;
+ set persistent synchronous_commit To off;
+ set persistent synchronous_standby_names = 'standby1, standby2';
+ set persistent seq_page_cost = 0.9;
+ set persistent autovacuum_naptime To 30;
+ set persistent search_path = 'public';
+ set persistent default_tablespace = '';
+ set persistent checkpoint_timeout = 1;
+ set persistent checkpoint_timeout = 3700;
+ set persistent checkpoint_timeout = 90;
+ set persistent restart_after_crash TO on;
+ 
+ 
+ show log_connections;
+ 
+ show max_connections;
+ show wal_level;
+ 
+ show authentication_timeout;
+ show vacuum_cost_delay;
+ show bgwriter_lru_multiplier;
+ show full_page_writes;
+ show synchronous_commit;
+ show synchronous_standby_names;
+ show seq_page_cost;
+ show autovacuum_naptime;
+ show search_path;
+ show default_tablespace;
+ show checkpoint_timeout;
+ show restart_after_crash;
+ 
+ -- reload the new configurations.
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show log_connections;
+ 
+ show max_connections;
+ show wal_level;
+ 
+ show authentication_timeout;
+ show vacuum_cost_delay;
+ show bgwriter_lru_multiplier;
+ show full_page_writes;
+ show synchronous_commit;
+ show synchronous_standby_names;
+ show seq_page_cost;
+ show autovacuum_naptime;
+ show search_path;
+ show default_tablespace;
+ show checkpoint_timeout;
+ show restart_after_crash;
+ 
+ 
+ -- reconnect to see the new configurations
+ \c
+ 
+ select name, setting from pg_settings where name = 'log_connections';
+ 
+ select name, setting from pg_settings where name = 'max_connections';
+ select name, setting from pg_settings where name = 'wal_level';
+ 
+ select name, setting from pg_settings where name = 'authentication_timeout';
+ select name, setting from pg_settings where name = 'vacuum_cost_delay';
+ select name, setting from pg_settings where name = 'bgwriter_lru_multiplier';
+ select name, setting from pg_settings where name = 'full_page_writes';
+ select name, setting from pg_settings where name = 'synchronous_commit';
+ select name, setting from pg_settings where name = 'synchronous_standby_names';
+ select name, setting from pg_settings where name = 'seq_page_cost';
+ select name, setting from pg_settings where name = 'autovacuum_naptime';
+ select name, setting from pg_settings where name = 'search_path';
+ select name, setting from pg_settings where name = 'default_tablespace';
+ select name, setting from pg_settings where name = 'checkpoint_timeout';
+ select name, setting from pg_settings where name = 'restart_after_crash';
+ 
+ -- Reset the some of the parameters which are set in above
+ set persistent log_connections = default;
+ 
+ set persistent max_connections To default;
+ 
+ set persistent authentication_timeout To default;
+ set persistent synchronous_commit = default;
+ set persistent restart_after_crash To default;
+ 
+ -- reload the new configurations.
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ select name, setting from pg_settings where name = 'log_connections';
+ select name, setting from pg_settings where name = 'max_connections';
+ select name, setting from pg_settings where name = 'authentication_timeout';
+ select name, setting from pg_settings where name = 'seq_page_cost';
+ select name, setting from pg_settings where name = 'restart_after_crash';
+ 
+ -- reconnect to see the new configurations
+ \c
+ 
+ show log_connections;
+ show max_connections;
+ show authentication_timeout;
+ show seq_page_cost;
+ show restart_after_crash;
+ 
+ -- set the parameters again which are reset above.
+ set persistent log_connections To yes;
+ 
+ set persistent max_connections = 50;
+ 
+ set persistent authentication_timeout = 20;
+ set persistent synchronous_commit To off;
+ set persistent restart_after_crash To yes;
+ 
+ -- reload the new configurations.
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show log_connections;
+ show max_connections;
+ show authentication_timeout;
+ show seq_page_cost;
+ show restart_after_crash;
+ 
+ -- reconnect to see the new configurations
+ \c
+ show log_connections;
+ show max_connections;
+ show authentication_timeout;
+ show seq_page_cost;
+ show restart_after_crash;
+ 
+ -- set a configuration param inside a function
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ set persistent enable_hashagg=off;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ 
+ select persistent_func();
+ 
+ show enable_hashagg;
+ 
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show enable_hashagg;
+ 
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ set persistent enable_hashagg=default;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ 
+ select persistent_func();
+ 
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show enable_hashagg;
+ 
+ Drop function persistent_func();
+ 
+ -- Reset all parameters which are set at above.
+ set persistent log_connections To default;
+ 
+ set persistent max_connections = default;
+ set persistent wal_level To default;
+ 
+ set persistent authentication_timeout To default;
+ set persistent vacuum_cost_delay = default;
+ set persistent bgwriter_lru_multiplier To default;
+ set persistent full_page_writes To default;
+ set persistent synchronous_commit = default;
+ set persistent synchronous_standby_names To default;
+ set persistent seq_page_cost To default;
+ set persistent autovacuum_naptime = default;
+ set persistent search_path To default;
+ set persistent default_tablespace To default;
+ set persistent checkpoint_timeout To default;
+ set persistent restart_after_crash = default;
+ 
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ 
+ -- Normal user tries to set
+ create user test password 'test';
+ SET SESSION AUTHORIZATION test;
+ set persistent enable_seqscan=off;
+ \c -
+ drop user test;
+ 
+ -- In a transaction block tries to set
+ start transaction;
+ set persistent enable_hashagg=off;
+ commit;
+ 
+ start transaction;
+ set persistent enable_hashagg=default;
+ commit;
+ 

diff -dcrpN postgresql.1/src/backend/utils/misc/guc.c postgresql.2/src/backend/utils/misc/guc.c
*** postgresql.1/src/backend/utils/misc/guc.c	2013-01-04 12:43:00.023640391 +0100
--- postgresql.2/src/backend/utils/misc/guc.c	2013-01-04 18:21:01.654437283 +0100
***************
*** 63,68 ****
--- 63,69 ----
  #include "storage/bufmgr.h"
  #include "storage/standby.h"
  #include "storage/fd.h"
+ #include "storage/lwlock.h"
  #include "storage/proc.h"
  #include "storage/predicate.h"
  #include "tcop/tcopprot.h"
*************** static int
*** 6097,6138 ****
  create_conf_lock_file(const char *LockFileName)
  {
  	int			fd;
- 	int			ntries;
  
! 	/*
! 	 * We need a loop here because of race conditions. Retry for 100 times.
! 	 */
! 	for (ntries = 0;; ntries++)
  	{
- 		fd = open(LockFileName, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
- 		if (fd >= 0)
- 			break;
- 
  		/*
! 		 * Couldn't create the lock file. Probably it already exists. If so
! 		 * wait for some time
  		 */
! 		if ((errno != EEXIST && errno != EACCES) || ntries > 100)
  		{
! 			if (errno != EEXIST)
! 			{
! 				ereport(ERROR,
  						(errcode_for_file_access(),
  						 errmsg("could not create lock file \"%s\": %m",
  								LockFileName)));
! 			}
! 			else
! 			{
! 				ereport(ERROR,
  						(errcode_for_file_access(),
  						 errmsg("could not create lock file \"%s\": %m ", LockFileName),
  						 errhint("May be too many concurrent edit into file happening, please wait!! and retry"
  								 "or .lock is file accidently left there please clean the file from config_dir")));
- 			}
- 		}
- 		else
- 		{
- 			pg_usleep(100000);	/* in total wait for 10sec */
  		}
  	}
  
--- 6098,6124 ----
  create_conf_lock_file(const char *LockFileName)
  {
  	int			fd;
  
! 	fd = open(LockFileName, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
! 	if (fd < 0)
  	{
  		/*
! 		 * Couldn't create the lock file. Probably it already exists.
  		 */
! 		if (errno != EEXIST)
  		{
! 			ereport(ERROR,
  						(errcode_for_file_access(),
  						 errmsg("could not create lock file \"%s\": %m",
  								LockFileName)));
! 		}
! 		else
! 		{
! 			ereport(ERROR,
  						(errcode_for_file_access(),
  						 errmsg("could not create lock file \"%s\": %m ", LockFileName),
  						 errhint("May be too many concurrent edit into file happening, please wait!! and retry"
  								 "or .lock is file accidently left there please clean the file from config_dir")));
  		}
  	}
  
*************** set_config_file(VariableSetStmt *setstmt
*** 6325,6330 ****
--- 6311,6318 ----
  	ConfAutoFileName = AbsoluteConfigLocation(AutoConfigFileName, ConfigFileName);
  	LockFileName = AbsoluteConfigLocation(AutoConfigLockFilename, ConfigFileName);
  
+ 	LWLockAcquire(SetPersistentLock, LW_EXCLUSIVE);
+ 
  	lockfd = create_conf_lock_file(LockFileName);
  
  	PG_TRY();
*************** set_config_file(VariableSetStmt *setstmt
*** 6382,6387 ****
--- 6370,6384 ----
  		PG_RE_THROW();
  	}
  	PG_END_TRY();
+ 
+ 	/*
+ 	 * Intentionally wait for 15 seconds here to simulate race conditions.
+ 	 * Remove this line when you've done enough testing.
+ 	 */
+ 	pg_usleep(15000000);
+ 
+ 	LWLockRelease(SetPersistentLock);
+ 
  	return;
  }
  
diff -dcrpN postgresql.1/src/include/storage/lwlock.h postgresql.2/src/include/storage/lwlock.h
*** postgresql.1/src/include/storage/lwlock.h	2013-01-02 09:19:03.906522364 +0100
--- postgresql.2/src/include/storage/lwlock.h	2013-01-04 17:57:51.058854977 +0100
*************** typedef enum LWLockId
*** 79,84 ****
--- 79,85 ----
  	SerializablePredicateLockListLock,
  	OldSerXidLock,
  	SyncRepLock,
+ 	SetPersistentLock,
  	/* Individual lock IDs end here */
  	FirstBufMappingLock,
  	FirstLockMgrLock = FirstBufMappingLock + NUM_BUFFER_PARTITIONS,

*** a/doc/src/sgml/keywords.sgml
--- b/doc/src/sgml/keywords.sgml
***************
*** 3388,3393 ****
--- 3388,3401 ----
      <entry></entry>
     </row>
     <row>
+    <row>
+     <entry><token>PERSISTENT</token></entry>
+     <entry>non-reserved</entry>
+     <entry></entry>
+     <entry></entry>
+     <entry></entry>
+    </row>
+    <row>
      <entry><token>PLACING</token></entry>
      <entry>reserved</entry>
      <entry>non-reserved</entry>
*** a/doc/src/sgml/ref/set.sgml
--- b/doc/src/sgml/ref/set.sgml
***************
*** 21,28 **** PostgreSQL documentation
  
   <refsynopsisdiv>
  <synopsis>
! SET [ SESSION | LOCAL ] <replaceable class="PARAMETER">configuration_parameter</replaceable> { TO | = } { <replaceable class="PARAMETER">value</replaceable> | '<replaceable class="PARAMETER">value</replaceable>' | DEFAULT }
! SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</replaceable> | LOCAL | DEFAULT }
  </synopsis>
   </refsynopsisdiv>
  
--- 21,28 ----
  
   <refsynopsisdiv>
  <synopsis>
! SET [ SESSION | LOCAL | PERSISTENT ] <replaceable class="PARAMETER">configuration_parameter</replaceable> { TO | = } { <replaceable class="PARAMETER">value</replaceable> | '<replaceable class="PARAMETER">value</replaceable>' | DEFAULT }
! SET [ SESSION | LOCAL | PERSISTENT ] TIME ZONE { <replaceable class="PARAMETER">timezone</replaceable> | LOCAL | DEFAULT }
  </synopsis>
   </refsynopsisdiv>
  
***************
*** 50,55 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
--- 50,64 ----
    </para>
  
    <para>
+    The <command>SET PERSISTENT</command> write the configuration parameter values to
+    <filename>postgresql.auto.conf</filename> file. with <literal>DEFAULT</literal> write the 
+    configuration parameter values to default value in <filename>postgresql.auto.conf</filename> file.
+    For deleting configuration entry in <filename>postgresql.auto.conf</filename> file use the 
+    <command>RESET PERSISTENT</command>. The values will be effective after reload of 
+    server configuration (SIGHUP) or server startup.  
+   </para>
+   
+   <para>
     The effects of <command>SET LOCAL</command> last only till the end of
     the current transaction, whether committed or not.  A special case is
     <command>SET</command> followed by <command>SET LOCAL</command> within
***************
*** 98,105 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
      <listitem>
       <para>
        Specifies that the command takes effect for the current session.
!       (This is the default if neither <literal>SESSION</> nor
!       <literal>LOCAL</> appears.)
       </para>
      </listitem>
     </varlistentry>
--- 107,114 ----
      <listitem>
       <para>
        Specifies that the command takes effect for the current session.
!       (This is the default option, if any of <literal>SESSION</>, 
!       <literal>LOCAL</> or <literal>PERSISTENT</> are not provided.)
       </para>
      </listitem>
     </varlistentry>
***************
*** 119,124 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
--- 128,144 ----
     </varlistentry>
  
     <varlistentry>
+     <term><literal>PERSISTENT</></term>
+     <listitem>
+      <para>
+       Writes updated configuration paramters in <filename>postgresql.auto.conf</filename>.
+       These configuration parameters takes effect after reload of configuration
+       file (SIGHUP) or in next server start based on type of configuration parameter modified.
+      </para>
+     </listitem>
+    </varlistentry>
+ 
+    <varlistentry>
      <term><replaceable class="PARAMETER">configuration_parameter</replaceable></term>
      <listitem>
       <para>
***************
*** 154,160 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
      <varlistentry>
       <term><literal>SCHEMA</literal></term>
       <listitem>
!       <para><literal>SET SCHEMA '<replaceable>value</>'</> is an alias for
         <literal>SET search_path TO <replaceable>value</></>.  Only one
         schema can be specified using this syntax.
        </para>
--- 174,180 ----
      <varlistentry>
       <term><literal>SCHEMA</literal></term>
       <listitem>
!       <para><literal>SET [ PERSISTENT ] SCHEMA '<replaceable>value</>'</> is an alias for
         <literal>SET search_path TO <replaceable>value</></>.  Only one
         schema can be specified using this syntax.
        </para>
***************
*** 164,170 **** SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
      <varlistentry>
       <term><literal>NAMES</literal></term>
       <listitem>
!       <para><literal>SET NAMES <replaceable>value</></> is an alias for
         <literal>SET client_encoding TO <replaceable>value</></>.
        </para>
       </listitem>
--- 184,190 ----
      <varlistentry>
       <term><literal>NAMES</literal></term>
       <listitem>
!       <para><literal>SET [ PERSISTENT ] NAMES <replaceable>value</></> is an alias for
         <literal>SET client_encoding TO <replaceable>value</></>.
        </para>
       </listitem>
***************
*** 192,198 **** SELECT setseed(<replaceable>value</replaceable>);
      <varlistentry>
       <term><literal>TIME ZONE</literal></term>
       <listitem>
!       <para><literal>SET TIME ZONE <replaceable>value</></> is an alias
         for <literal>SET timezone TO <replaceable>value</></>.  The
         syntax <literal>SET TIME ZONE</literal> allows special syntax
         for the time zone specification.  Here are examples of valid
--- 212,218 ----
      <varlistentry>
       <term><literal>TIME ZONE</literal></term>
       <listitem>
!       <para><literal>SET [ PERSISTENT ] TIME ZONE <replaceable>value</></> is an alias
         for <literal>SET timezone TO <replaceable>value</></>.  The
         syntax <literal>SET TIME ZONE</literal> allows special syntax
         for the time zone specification.  Here are examples of valid
*** a/src/backend/nodes/copyfuncs.c
--- b/src/backend/nodes/copyfuncs.c
***************
*** 3264,3269 **** _copyVariableSetStmt(const VariableSetStmt *from)
--- 3264,3270 ----
  	COPY_STRING_FIELD(name);
  	COPY_NODE_FIELD(args);
  	COPY_SCALAR_FIELD(is_local);
+ 	COPY_SCALAR_FIELD(is_persistent);
  
  	return newnode;
  }
*** a/src/backend/nodes/equalfuncs.c
--- b/src/backend/nodes/equalfuncs.c
***************
*** 1555,1560 **** _equalVariableSetStmt(const VariableSetStmt *a, const VariableSetStmt *b)
--- 1555,1561 ----
  	COMPARE_STRING_FIELD(name);
  	COMPARE_NODE_FIELD(args);
  	COMPARE_SCALAR_FIELD(is_local);
+ 	COMPARE_SCALAR_FIELD(is_persistent);
  
  	return true;
  }
*** a/src/backend/parser/gram.y
--- b/src/backend/parser/gram.y
***************
*** 394,400 **** static void processCASbits(int cas_bits, int location, const char *constrType,
  
  %type <istmt>	insert_rest
  
! %type <vsetstmt> set_rest set_rest_more SetResetClause FunctionSetResetClause
  
  %type <node>	TableElement TypedTableElement ConstraintElem TableFuncElement
  				ForeignTableElement
--- 394,400 ----
  
  %type <istmt>	insert_rest
  
! %type <vsetstmt> set_rest set_rest_common set_rest_more SetResetClause FunctionSetResetClause
  
  %type <node>	TableElement TypedTableElement ConstraintElem TableFuncElement
  				ForeignTableElement
***************
*** 564,571 **** static void processCASbits(int cas_bits, int location, const char *constrType,
  	OBJECT_P OF OFF OFFSET OIDS ON ONLY OPERATOR OPTION OPTIONS OR
  	ORDER OUT_P OUTER_P OVER OVERLAPS OVERLAY OWNED OWNER
  
! 	PARSER PARTIAL PARTITION PASSING PASSWORD PLACING PLANS POSITION
! 	PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY
  	PRIOR PRIVILEGES PROCEDURAL PROCEDURE
  
  	QUOTE
--- 564,571 ----
  	OBJECT_P OF OFF OFFSET OIDS ON ONLY OPERATOR OPTION OPTIONS OR
  	ORDER OUT_P OUTER_P OVER OVERLAPS OVERLAY OWNED OWNER
  
! 	PARSER PARTIAL PARTITION PASSING PASSWORD PERSISTENT PLACING PLANS
! 	POSITION PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY
  	PRIOR PRIVILEGES PROCEDURAL PROCEDURE
  
  	QUOTE
***************
*** 1293,1298 **** VariableSetStmt:
--- 1293,1304 ----
  					n->is_local = false;
  					$$ = (Node *) n;
  				}
+ 			| SET PERSISTENT set_rest_common
+ 				{
+ 					VariableSetStmt *n = $3;
+ 					n->is_persistent = true;
+ 					$$ = (Node *) n;
+ 				}
  		;
  
  set_rest:
***************
*** 1315,1321 **** set_rest:
  			| set_rest_more
  			;
  
! set_rest_more:	/* Generic SET syntaxes: */
  			var_name TO var_list
  				{
  					VariableSetStmt *n = makeNode(VariableSetStmt);
--- 1321,1327 ----
  			| set_rest_more
  			;
  
! set_rest_common:	/* common SET syntaxes: */
  			var_name TO var_list
  				{
  					VariableSetStmt *n = makeNode(VariableSetStmt);
***************
*** 1346,1358 **** set_rest_more:	/* Generic SET syntaxes: */
  					n->name = $1;
  					$$ = n;
  				}
- 			| var_name FROM CURRENT_P
- 				{
- 					VariableSetStmt *n = makeNode(VariableSetStmt);
- 					n->kind = VAR_SET_CURRENT;
- 					n->name = $1;
- 					$$ = n;
- 				}
  			/* Special syntaxes mandated by SQL standard: */
  			| TIME ZONE zone_value
  				{
--- 1352,1357 ----
***************
*** 1365,1378 **** set_rest_more:	/* Generic SET syntaxes: */
  						n->kind = VAR_SET_DEFAULT;
  					$$ = n;
  				}
- 			| CATALOG_P Sconst
- 				{
- 					ereport(ERROR,
- 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
- 							 errmsg("current database cannot be changed"),
- 							 parser_errposition(@2)));
- 					$$ = NULL; /*not reached*/
- 				}
  			| SCHEMA Sconst
  				{
  					VariableSetStmt *n = makeNode(VariableSetStmt);
--- 1364,1369 ----
***************
*** 1381,1386 **** set_rest_more:	/* Generic SET syntaxes: */
--- 1372,1404 ----
  					n->args = list_make1(makeStringConst($2, @2));
  					$$ = n;
  				}
+ 			| XML_P OPTION document_or_content
+ 				{
+ 					VariableSetStmt *n = makeNode(VariableSetStmt);
+ 					n->kind = VAR_SET_VALUE;
+ 					n->name = "xmloption";
+ 					n->args = list_make1(makeStringConst($3 == XMLOPTION_DOCUMENT ? "DOCUMENT" : "CONTENT", @3));
+ 					$$ = n;
+ 				}
+ 			;
+ 
+ set_rest_more:	/* Generic SET syntaxes: */
+ 			set_rest_common
+ 			| var_name FROM CURRENT_P
+ 				{
+ 					VariableSetStmt *n = makeNode(VariableSetStmt);
+ 					n->kind = VAR_SET_CURRENT;
+ 					n->name = $1;
+ 					$$ = n;
+ 				}
+ 			| CATALOG_P Sconst
+ 				{
+ 					ereport(ERROR,
+ 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ 							 errmsg("current database cannot be changed"),
+ 							 parser_errposition(@2)));
+ 					$$ = NULL; /*not reached*/
+ 				}
  			| NAMES opt_encoding
  				{
  					VariableSetStmt *n = makeNode(VariableSetStmt);
***************
*** 1415,1428 **** set_rest_more:	/* Generic SET syntaxes: */
  					n->name = "session_authorization";
  					$$ = n;
  				}
- 			| XML_P OPTION document_or_content
- 				{
- 					VariableSetStmt *n = makeNode(VariableSetStmt);
- 					n->kind = VAR_SET_VALUE;
- 					n->name = "xmloption";
- 					n->args = list_make1(makeStringConst($3 == XMLOPTION_DOCUMENT ? "DOCUMENT" : "CONTENT", @3));
- 					$$ = n;
- 				}
  			/* Special syntaxes invented by PostgreSQL: */
  			| TRANSACTION SNAPSHOT Sconst
  				{
--- 1433,1438 ----
***************
*** 12590,12595 **** unreserved_keyword:
--- 12600,12606 ----
  			| PARTITION
  			| PASSING
  			| PASSWORD
+ 			| PERSISTENT
  			| PLANS
  			| PRECEDING
  			| PREPARE
*** a/src/backend/postmaster/postmaster.c
--- b/src/backend/postmaster/postmaster.c
***************
*** 2552,2557 **** reaper(SIGNAL_ARGS)
--- 2552,2569 ----
  				continue;
  			}
  
+ 			/* Delete the postgresql.auto.conf.lock file if exists */
+ 			{
+ 				char		LockFileName[MAXPGPATH];
+ 
+ 				strlcpy(LockFileName, ConfigFileName, sizeof(LockFileName));
+ 				get_parent_directory(LockFileName);
+ 				join_path_components(LockFileName, LockFileName, AutoConfigLockFilename);
+ 				canonicalize_path(LockFileName);
+ 
+ 				unlink(LockFileName);
+ 			}
+ 
  			/*
  			 * Startup succeeded, commence normal operations
  			 */
*** a/src/backend/replication/basebackup.c
--- b/src/backend/replication/basebackup.c
***************
*** 736,741 **** sendDir(char *path, int basepathlen, bool sizeonly)
--- 736,747 ----
  					strlen(PG_TEMP_FILE_PREFIX)) == 0)
  			continue;
  
+ 		/* skip lock files used in postgresql.auto.conf edit */
+ 		if (strncmp(de->d_name,
+ 					PGAUTOCONFLOCK,
+ 					sizeof(PGAUTOCONFLOCK)) == 0)
+ 			continue;
+ 
  		/*
  		 * If there's a backup_label file, it belongs to a backup started by
  		 * the user with pg_start_backup(). It is *not* correct for this
*** a/src/backend/utils/misc/guc-file.l
--- b/src/backend/utils/misc/guc-file.l
***************
*** 41,46 **** enum {
--- 41,47 ----
  	GUC_ERROR = 100
  };
  
+ static bool is_config_dir_parsed = false;
  static unsigned int ConfigFileLineno;
  static const char *GUC_flex_fatal_errmsg;
  static sigjmp_buf *GUC_flex_fatal_jmp;
***************
*** 137,142 **** ProcessConfigFile(GucContext context)
--- 138,145 ----
  	/* Parse the file into a list of option names and values */
  	head = tail = NULL;
  
+ 	is_config_dir_parsed = false;
+ 
  	if (!ParseConfigFile(ConfigFileName, NULL, true, 0, elevel, &head, &tail))
  	{
  		/* Syntax error(s) detected in the file, so bail out */
***************
*** 144,149 **** ProcessConfigFile(GucContext context)
--- 147,159 ----
  		goto cleanup_list;
  	}
  
+ 	if (!is_config_dir_parsed)
+ 	{
+ 		ereport(WARNING,
+ 				(errmsg("Default \"config_dir\" is not present in postgresql.conf."
+ 						"Any configuration value changed with SET PERSISTENT command will not be effective.")));
+ 	}
+ 
  	/*
  	 * Mark all extant GUC variables as not present in the config file.
  	 * We need this so that we can tell below which ones have been removed
***************
*** 367,373 **** ProcessConfigFile(GucContext context)
   * path, return an absolute one.  We consider the location to be relative to
   * the directory holding the calling file.
   */
! static char *
  AbsoluteConfigLocation(const char *location, const char *calling_file)
  {
  	char		abs_path[MAXPGPATH];
--- 377,383 ----
   * path, return an absolute one.  We consider the location to be relative to
   * the directory holding the calling file.
   */
! char *
  AbsoluteConfigLocation(const char *location, const char *calling_file)
  {
  	char		abs_path[MAXPGPATH];
***************
*** 411,416 **** ParseConfigFile(const char *config_file, const char *calling_file, bool strict,
--- 421,427 ----
  {
  	bool		OK = true;
  	FILE	   *fp;
+ 	char 		*ConfigAutoFileName;
  
  	/*
  	 * Reject too-deep include nesting depth.  This is just a safety check
***************
*** 427,432 **** ParseConfigFile(const char *config_file, const char *calling_file, bool strict,
--- 438,449 ----
  	}
  
  	config_file = AbsoluteConfigLocation(config_file,calling_file);
+ 
+ 	/* Checking for the postgresql.auto.conf file is parsed or not */
+ 	ConfigAutoFileName = AbsoluteConfigLocation(AutoConfigFileName, ConfigFileName);
+ 	if (depth == 1 && strcmp(ConfigAutoFileName, config_file) == 0)
+ 		is_config_dir_parsed = true;
+ 
  	fp = AllocateFile(config_file, "r");
  	if (!fp)
  	{
***************
*** 533,538 **** ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
--- 550,556 ----
  	{
  		char	   *opt_name = NULL;
  		char	   *opt_value = NULL;
+ 		bool		is_string = false;
  		ConfigVariable *item;
  
  		if (token == GUC_EOL)	/* empty or comment line */
***************
*** 556,562 **** ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
--- 574,583 ----
  			token != GUC_UNQUOTED_STRING)
  			goto parse_error;
  		if (token == GUC_STRING)	/* strip quotes and escapes */
+ 		{
  			opt_value = GUC_scanstr(yytext);
+ 			is_string = true;
+ 		}
  		else
  			opt_value = pstrdup(yytext);
  
***************
*** 620,625 **** ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
--- 641,647 ----
  			item = palloc(sizeof *item);
  			item->name = opt_name;
  			item->value = opt_value;
+ 			item->is_quoted = is_string;
  			item->filename = pstrdup(config_file);
  			item->sourceline = ConfigFileLineno-1;
  			item->next = NULL;
*** a/src/backend/utils/misc/guc.c
--- b/src/backend/utils/misc/guc.c
***************
*** 63,68 ****
--- 63,69 ----
  #include "storage/bufmgr.h"
  #include "storage/standby.h"
  #include "storage/fd.h"
+ #include "storage/lwlock.h"
  #include "storage/proc.h"
  #include "storage/predicate.h"
  #include "tcop/tcopprot.h"
***************
*** 3348,3353 **** static void ShowAllGUCConfig(DestReceiver *dest);
--- 3349,3359 ----
  static char *_ShowOption(struct config_generic * record, bool use_units);
  static bool validate_option_array_item(const char *name, const char *value,
  						   bool skipIfNoPermissions);
+ static int	create_conf_lock_file(const char *LockFileName);
+ static void write_auto_conf_file(int fd, ConfigVariable **head_p);
+ static void replace_auto_config_value(ConfigVariable **head_p, ConfigVariable **tail_p,
+ 				 char *config_file, char *name, char *value, bool is_quoted);
+ static void set_config_file(VariableSetStmt *setstmt);
  
  
  /*
***************
*** 4120,4125 **** SelectConfigFiles(const char *userDoption, const char *progname)
--- 4126,4140 ----
  		return false;
  	}
  
+ 	/* Remove postgresql.auto.conf.lock file make be left over from last crash */
+ 	if (!IsUnderPostmaster)
+ 	{
+ 		char	   *LockFileName;
+ 
+ 		LockFileName = AbsoluteConfigLocation(AutoConfigLockFilename, ConfigFileName);
+ 		unlink(LockFileName);
+ 	}
+ 
  	ProcessConfigFile(PGC_POSTMASTER);
  
  	/*
***************
*** 5094,5099 **** config_enum_get_options(struct config_enum * record, const char *prefix,
--- 5109,5293 ----
  	return retstr.data;
  }
  
+ /*
+  * Validates configuration parameter and value, incase of source is default
+  * returns the default value in string format.
+  */
+ struct config_generic *
+ validate_conf_option(const char *name, char *value)
+ {
+ 	struct config_generic *record;
+ 
+ 	record = find_option(name, true, LOG);
+ 	if (record == NULL)
+ 	{
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_UNDEFINED_OBJECT),
+ 			   errmsg("unrecognized configuration parameter \"%s\"", name)));
+ 	}
+ 
+ 	if (record->context == PGC_INTERNAL)
+ 	{
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
+ 				 errmsg("parameter \"%s\" cannot be changed",
+ 						name)));
+ 	}
+ 
+ 	/*
+ 	 * Evaluate value and set variable.
+ 	 */
+ 	switch (record->vartype)
+ 	{
+ 
+ 		case PGC_BOOL:
+ 			{
+ 				struct config_bool *conf = (struct config_bool *) record;
+ 				bool		newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					if (!parse_bool(value, &newval))
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						  errmsg("parameter \"%s\" requires a Boolean value",
+ 								 name)));
+ 					}
+ 					if (!call_bool_check_hook(conf, &newval, &newextra,
+ 											  PGC_S_FILE, LOG))
+ 						return NULL;
+ 				}
+ 			}
+ 			break;
+ 		case PGC_INT:
+ 			{
+ 				struct config_int *conf = (struct config_int *) record;
+ 				int			newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					const char *hintmsg;
+ 
+ 					if (!parse_int(value, &newval, conf->gen.flags, &hintmsg))
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						 errmsg("invalid value for parameter \"%s\": \"%s\"",
+ 								name, value),
+ 								 hintmsg ? errhint("%s", _(hintmsg)) : 0));
+ 					}
+ 					if (newval < conf->min || newval > conf->max)
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 								 errmsg("%d is outside the valid range for parameter \"%s\" (%d .. %d)",
+ 										newval, name, conf->min, conf->max)));
+ 					}
+ 					if (!call_int_check_hook(conf, &newval, &newextra,
+ 											 PGC_S_FILE, LOG))
+ 						return NULL;
+ 				}
+ 			}
+ 			break;
+ 		case PGC_REAL:
+ 			{
+ 				struct config_real *conf = (struct config_real *) record;
+ 				double		newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					if (!parse_real(value, &newval))
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						  errmsg("parameter \"%s\" requires a numeric value",
+ 								 name)));
+ 					}
+ 					if (newval < conf->min || newval > conf->max)
+ 					{
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 								 errmsg("%g is outside the valid range for parameter \"%s\" (%g .. %g)",
+ 										newval, name, conf->min, conf->max)));
+ 					}
+ 					if (!call_real_check_hook(conf, &newval, &newextra,
+ 											  PGC_S_FILE, LOG))
+ 						return NULL;
+ 				}
+ 			}
+ 			break;
+ 		case PGC_STRING:
+ 			{
+ 				struct config_string *conf = (struct config_string *) record;
+ 				char	   *newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					/*
+ 					 * The value passed by the caller could be transient, so
+ 					 * we always strdup it.
+ 					 */
+ 					newval = guc_strdup(LOG, value);
+ 					if (newval == NULL)
+ 						return NULL;
+ 
+ 					/*
+ 					 * The only built-in "parsing" check we have is to apply
+ 					 * truncation if GUC_IS_NAME.
+ 					 */
+ 					if (conf->gen.flags & GUC_IS_NAME)
+ 						truncate_identifier(newval, strlen(newval), true);
+ 
+ 					if (!call_string_check_hook(conf, &newval, &newextra,
+ 												PGC_S_FILE, LOG))
+ 					{
+ 						free(newval);
+ 						return NULL;
+ 					}
+ 				}
+ 			}
+ 			break;
+ 		case PGC_ENUM:
+ 			{
+ 				struct config_enum *conf = (struct config_enum *) record;
+ 				int			newval;
+ 				void	   *newextra = NULL;
+ 
+ 				if (value)
+ 				{
+ 					if (!config_enum_lookup_by_name(conf, value, &newval))
+ 					{
+ 						char	   *hintmsg;
+ 
+ 						hintmsg = config_enum_get_options(conf,
+ 														"Available values: ",
+ 														  ".", ", ");
+ 
+ 						ereport(ERROR,
+ 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ 						 errmsg("invalid value for parameter \"%s\": \"%s\"",
+ 								name, value),
+ 								 hintmsg ? errhint("%s", _(hintmsg)) : 0));
+ 
+ 						if (hintmsg)
+ 							pfree(hintmsg);
+ 						return 0;
+ 					}
+ 					if (!call_enum_check_hook(conf, &newval, &newextra,
+ 											  PGC_S_FILE, LOG))
+ 						return 0;
+ 				}
+ 			}
+ 	}
+ 
+ 	return record;
+ }
+ 
  
  /*
   * Sets option `name' to given value.
***************
*** 5897,5902 **** set_config_sourcefile(const char *name, char *sourcefile, int sourceline)
--- 6091,6380 ----
  }
  
  /*
+  * Creates auto conf lock file used for protecting modification of
+  * postgresql.auto.conf file.
+  */
+ static int
+ create_conf_lock_file(const char *LockFileName)
+ {
+ 	int			fd;
+ 
+ 	fd = open(LockFileName, O_CREAT | O_RDWR | O_EXCL, S_IRUSR | S_IWUSR);
+ 	if (fd < 0)
+ 	{
+ 		/* Couldn't create the lock file. Probably it already exists */
+ 		if (errno != EEXIST)
+ 		{
+ 			ereport(ERROR,
+ 					(errcode_for_file_access(),
+ 					 errmsg("could not create lock file \"%s\": %m",
+ 							LockFileName)));
+ 		}
+ 		else
+ 		{
+ 			ereport(ERROR,
+ 					(errcode_for_file_access(),
+ 			  errmsg("could not create lock file \"%s\": %m ", LockFileName),
+ 					 errhint("May be too many concurrent edit into file happening, please wait!! and retry "
+ 							 "or .lock is file accidently left there please clean the file from config_dir")));
+ 		}
+ 	}
+ 
+ 	return fd;
+ }
+ 
+ 
+ /* Write updated configuration parameter values into postgresql.auto.conf.lock */
+ static void
+ write_auto_conf_file(int fd, ConfigVariable **head_p)
+ {
+ 	ConfigVariable *item;
+ 	StringInfoData buf;
+ 
+ 	initStringInfo(&buf);
+ 
+ 	for (item = *head_p; item != NULL; item = item->next)
+ 	{
+ 		appendStringInfoString(&buf, item->name);
+ 		appendStringInfoString(&buf, " = ");
+ 
+ 		if (true == item->is_quoted)
+ 		{
+ 			appendStringInfoString(&buf, "\'");
+ 			appendStringInfoString(&buf, item->value);
+ 			appendStringInfoString(&buf, "\'");
+ 		}
+ 		else
+ 		{
+ 			appendStringInfoString(&buf, item->value);
+ 		}
+ 
+ 		appendStringInfoString(&buf, "\n");
+ 
+ 		if (write(fd, buf.data, buf.len) < 0)
+ 		{
+ 			ereport(ERROR,
+ 					(errmsg("failed to write into to \"postgresql.auto.conf.lock\" file")));
+ 		}
+ 
+ 		resetStringInfo(&buf);
+ 	}
+ 
+ 	if (pg_fsync(fd) != 0)
+ 		ereport(ERROR,
+ 				(errcode_for_file_access(),
+ 		  errmsg("could not fsync file \"postgresql.auto.conf.lock\": %m")));
+ 
+ 
+ 	pfree(buf.data);
+ 	return;
+ }
+ 
+ 
+ /*
+  * Replace the updated configuration parameter value in postgresql.auto.conf
+  * file lines. If it is new then append extra line at the end of lines.
+  */
+ static void
+ replace_auto_config_value(ConfigVariable **head_p, ConfigVariable **tail_p,
+ 						  char *config_file, char *name, char *value,
+ 						  bool is_quoted)
+ {
+ 	ConfigVariable *item,
+ 			   *prev = NULL;
+ 
+ 	if (NULL != *head_p)
+ 	{
+ 		for (item = *head_p; item != NULL; item = item->next)
+ 		{
+ 			if (strcmp(item->name, name) == 0)
+ 			{
+ 				pfree(item->value);
+ 				if (value)
+ 				{
+ 					/* update the parameter value */
+ 					item->value = pstrdup(value);
+ 				}
+ 				else
+ 				{
+ 					/* delete the configuration parameter from list */
+ 					if (*head_p == item)
+ 					{
+ 						*head_p = item->next;
+ 					}
+ 					else
+ 					{
+ 						prev->next = item->next;
+ 					}
+ 
+ 					if (*tail_p == item)
+ 					{
+ 						*tail_p = prev;
+ 					}
+ 					pfree(item->name);
+ 					pfree(item->filename);
+ 					pfree(item);
+ 				}
+ 				return;
+ 			}
+ 			prev = item;
+ 		}
+ 	}
+ 
+ 	if (NULL == value)
+ 	{
+ 		return;
+ 	}
+ 
+ 	item = palloc(sizeof *item);
+ 	item->name = pstrdup(name);
+ 	item->value = pstrdup(value);
+ 	item->is_quoted = is_quoted;
+ 	item->filename = pstrdup(config_file);
+ 	item->next = NULL;
+ 
+ 	if (*head_p == NULL)
+ 	{
+ 		item->sourceline = 1;
+ 		*head_p = item;
+ 	}
+ 	else
+ 	{
+ 		item->sourceline = (*tail_p)->sourceline + 1;
+ 		(*tail_p)->next = item;
+ 	}
+ 
+ 	*tail_p = item;
+ 
+ 	return;
+ }
+ 
+ 
+ /*
+  * Persist the configuration parameter value.
+  * Writes the value of configuration parameter in postgresql.auto.conf.lock file.
+  * .lock file is used to disallow changing of file by multiple backends.
+  * On Success, rename postgresql.auto.conf.lock to postgresql.auto.conf
+  * and On Failure, delete the postgresql.auto.conf.lock
+  */
+ static void
+ set_config_file(VariableSetStmt *setstmt)
+ {
+ 	char	   *name;
+ 	char	   *value;
+ 	int			lockfd = -1;
+ 	FILE	   *infile;
+ 	struct config_generic *record;
+ 	ConfigVariable *head_p = NULL;
+ 	ConfigVariable *tail_p = NULL;
+ 	char	   *ConfAutoFileName;
+ 	char	   *LockFileName;
+ 	struct stat st;
+ 
+ 	if (!superuser())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+ 				 (errmsg("must be superuser to execute SET/RESET PERSISTENT command"))));
+ 
+ 	if (IsTransactionBlock())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_ACTIVE_SQL_TRANSACTION),
+ 				 (errmsg("SET/RESET PERSISTENT command cannot run inside a transaction block"))));
+ 
+ 	/*
+ 	 * Validate the name and arguments [value1, value2 ... ].
+ 	 */
+ 	name = setstmt->name;
+ 
+ 	switch (setstmt->kind)
+ 	{
+ 		case VAR_SET_VALUE:
+ 			value = ExtractSetVariableArgs(setstmt);
+ 			break;
+ 
+ 		case VAR_SET_DEFAULT:
+ 			value = NULL;
+ 			break;
+ 
+ 		default:
+ 			return;
+ 	}
+ 
+ 	record = validate_conf_option(name, value);
+ 	if (!record)
+ 		ereport(ERROR,
+ 		(errmsg("invalid value for parameter \"%s\": \"%s\"", name, value)));
+ 
+ 	/* Create the postgresql.auto.conf.lock file */
+ 	ConfAutoFileName = AbsoluteConfigLocation(AutoConfigFileName, ConfigFileName);
+ 	LockFileName = AbsoluteConfigLocation(AutoConfigLockFilename, ConfigFileName);
+ 
+ 	LWLockAcquire(SetPersistentLock, LW_EXCLUSIVE);
+ 
+ 	lockfd = create_conf_lock_file(LockFileName);
+ 
+ 	PG_TRY();
+ 	{
+ 		if (stat(ConfAutoFileName, &st) != 0)
+ 		{
+ 			int			fd;
+ 
+ 			fd = open(ConfAutoFileName, O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);
+ 			if (fd < 0)
+ 				ereport(ERROR,
+ 						(errcode_for_file_access(),
+ 						 errmsg("creation of auto conf file failed as it was not exist\"%s\": %m",
+ 								ConfAutoFileName)));
+ 			close(fd);
+ 
+ 			ereport(NOTICE,
+ 				 (errmsg("Created auto conf file as it was not exist \"%s\"",
+ 						 ConfAutoFileName)));
+ 		}
+ 
+ 		/* open postgresql.auto.conf file */
+ 		infile = AllocateFile(ConfAutoFileName, "r");
+ 		if (infile == NULL)
+ 			ereport(ERROR,
+ 					(errmsg("failed to open \"postgresql.auto.conf\" file")));
+ 
+ 		/* Parse the postgresql.auto.conf file */
+ 		ParseConfigFp(infile, ConfAutoFileName, 0, LOG, &head_p, &tail_p);
+ 
+ 		FreeFile(infile);
+ 
+ 		/* replace with new value */
+ 		replace_auto_config_value(&head_p, &tail_p, ConfAutoFileName, name,
+ 					  value, (record->vartype == PGC_STRING) ? true : false);
+ 
+ 		/* Write the New contents to postgresql.auto.conf.lock file */
+ 		write_auto_conf_file(lockfd, &head_p);
+ 
+ 		close(lockfd);
+ 		lockfd = -1;
+ 
+ 		if (rename(LockFileName, ConfAutoFileName) < 0)
+ 			ereport(ERROR,
+ 					(errcode_for_file_access(),
+ 					 errmsg("could not rename file \"%s\" to \"%s\" : %m",
+ 							LockFileName, ConfAutoFileName)));
+ 	}
+ 	PG_CATCH();
+ 	{
+ 		if (lockfd >= 0)
+ 			close(lockfd);
+ 
+ 		unlink(LockFileName);
+ 		PG_RE_THROW();
+ 	}
+ 	PG_END_TRY();
+ 
+ 	LWLockRelease(SetPersistentLock);
+ 	return;
+ }
+ 
+ 
+ /*
   * Set a config option to the given value.
   *
   * See also set_config_option; this is just the wrapper to be called from
***************
*** 6167,6172 **** ExecSetVariableStmt(VariableSetStmt *stmt)
--- 6645,6656 ----
  	switch (stmt->kind)
  	{
  		case VAR_SET_VALUE:
+ 			if (stmt->is_persistent)
+ 			{
+ 				set_config_file(stmt);
+ 				break;
+ 			}
+ 			/* FALLTHROUGH */
  		case VAR_SET_CURRENT:
  			(void) set_config_option(stmt->name,
  									 ExtractSetVariableArgs(stmt),
***************
*** 6246,6251 **** ExecSetVariableStmt(VariableSetStmt *stmt)
--- 6730,6741 ----
  					 stmt->name);
  			break;
  		case VAR_SET_DEFAULT:
+ 			if (stmt->is_persistent)
+ 			{
+ 				set_config_file(stmt);
+ 				break;
+ 			}
+ 			/* FALLTHROUGH */
  		case VAR_RESET:
  			(void) set_config_option(stmt->name,
  									 NULL,
*** a/src/backend/utils/misc/postgresql.conf.sample
--- b/src/backend/utils/misc/postgresql.conf.sample
***************
*** 581,586 ****
--- 581,593 ----
  #include_if_exists = 'exists.conf'	# include file only if it exists
  #include = 'special.conf'		# include file
  
+ # This includes the default configuration directory included to support
+ # SET PERSISTENT statement.
+ #
+ # WARNING: Any configuration parameter values specified after this line
+ #           will override the values set by SET PERSISTENT statement.
+ #include_dir = 'auto.conf.d'
+ 
  #------------------------------------------------------------------------------
  # CUSTOMIZED OPTIONS
  #------------------------------------------------------------------------------
*** a/src/bin/initdb/initdb.c
--- b/src/bin/initdb/initdb.c
***************
*** 192,198 **** const char *subdirs[] = {
  	"base",
  	"base/1",
  	"pg_tblspc",
! 	"pg_stat_tmp"
  };
  
  
--- 192,199 ----
  	"base",
  	"base/1",
  	"pg_tblspc",
! 	"pg_stat_tmp",
! 	"config_dir"
  };
  
  
***************
*** 1209,1214 **** setup_config(void)
--- 1210,1216 ----
  	char		repltok[MAXPGPATH];
  	char		path[MAXPGPATH];
  	const char *default_timezone;
+ 	FILE	   *autofile;
  
  	fputs(_("creating configuration files ... "), stdout);
  	fflush(stdout);
***************
*** 1291,1301 **** setup_config(void)
--- 1293,1326 ----
  		conflines = replace_token(conflines, "#log_timezone = 'GMT'", repltok);
  	}
  
+ 	snprintf(repltok, sizeof(repltok), "include_dir = 'config_dir'");
+ 	conflines = replace_token(conflines, "#include_dir = 'auto.conf.d'", repltok);
+ 
  	snprintf(path, sizeof(path), "%s/postgresql.conf", pg_data);
  
  	writefile(path, conflines);
  	chmod(path, S_IRUSR | S_IWUSR);
  
+ 	/* create a .auto for conf file */
+ 	sprintf(path, "%s/config_dir/postgresql.auto.conf", pg_data);
+ 	autofile = fopen(path, PG_BINARY_W);
+ 	if (autofile == NULL)
+ 	{
+ 		fprintf(stderr, _("%s: could not open file \"%s\" for writing: %s\n"),
+ 				progname, path, strerror(errno));
+ 		exit_nicely();
+ 	}
+ 
+ 	if (fclose(autofile))
+ 	{
+ 		fprintf(stderr, _("%s: could not write file \"%s\": %s\n"),
+ 				progname, path, strerror(errno));
+ 		exit_nicely();
+ 	}
+ 
+ 	chmod(path, S_IRUSR | S_IWUSR);
+ 
+ 
  	free(conflines);
  
  
*** a/src/include/nodes/parsenodes.h
--- b/src/include/nodes/parsenodes.h
***************
*** 1425,1430 **** typedef struct VariableSetStmt
--- 1425,1431 ----
  	char	   *name;			/* variable to be set */
  	List	   *args;			/* List of A_Const nodes */
  	bool		is_local;		/* SET LOCAL? */
+ 	bool		is_persistent;	/* SET PERSISTENT? */
  } VariableSetStmt;
  
  /* ----------------------
*** a/src/include/parser/kwlist.h
--- b/src/include/parser/kwlist.h
***************
*** 279,284 **** PG_KEYWORD("partial", PARTIAL, UNRESERVED_KEYWORD)
--- 279,285 ----
  PG_KEYWORD("partition", PARTITION, UNRESERVED_KEYWORD)
  PG_KEYWORD("passing", PASSING, UNRESERVED_KEYWORD)
  PG_KEYWORD("password", PASSWORD, UNRESERVED_KEYWORD)
+ PG_KEYWORD("persistent", PERSISTENT, UNRESERVED_KEYWORD)
  PG_KEYWORD("placing", PLACING, RESERVED_KEYWORD)
  PG_KEYWORD("plans", PLANS, UNRESERVED_KEYWORD)
  PG_KEYWORD("position", POSITION, COL_NAME_KEYWORD)
*** a/src/include/storage/lwlock.h
--- b/src/include/storage/lwlock.h
***************
*** 79,84 **** typedef enum LWLockId
--- 79,85 ----
  	SerializablePredicateLockListLock,
  	OldSerXidLock,
  	SyncRepLock,
+ 	SetPersistentLock,
  	/* Individual lock IDs end here */
  	FirstBufMappingLock,
  	FirstLockMgrLock = FirstBufMappingLock + NUM_BUFFER_PARTITIONS,
*** a/src/include/utils/guc.h
--- b/src/include/utils/guc.h
***************
*** 105,115 **** typedef struct ConfigVariable
--- 105,118 ----
  {
  	char	   *name;
  	char	   *value;
+ 	bool		is_quoted;
  	char	   *filename;
  	int			sourceline;
  	struct ConfigVariable *next;
  } ConfigVariable;
  
+ extern char *AbsoluteConfigLocation(const char *location,
+ 					   const char *calling_file);
  extern bool ParseConfigFile(const char *config_file, const char *calling_file,
  				bool strict, int depth, int elevel,
  				ConfigVariable **head_p, ConfigVariable **tail_p);
***************
*** 191,196 **** typedef enum
--- 194,204 ----
  
  #define GUC_NOT_WHILE_SEC_REST	0x8000	/* can't set if security restricted */
  
+ /* postgresql.auto.file name and its lock */
+ #define AutoConfigFileName "config_dir/postgresql.auto.conf"
+ #define AutoConfigLockFilename	"config_dir/postgresql.auto.conf.lock"
+ #define PGAUTOCONFLOCK	"postgresql.auto.conf.lock"
+ 
  /* GUC vars that are actually declared in guc.c, rather than elsewhere */
  extern bool log_duration;
  extern bool Debug_print_plan;
*** a/src/include/utils/guc_tables.h
--- b/src/include/utils/guc_tables.h
***************
*** 260,265 **** extern void build_guc_variables(void);
  extern const char *config_enum_lookup_by_value(struct config_enum * record, int val);
  extern bool config_enum_lookup_by_name(struct config_enum * record,
  						   const char *value, int *retval);
! 
  
  #endif   /* GUC_TABLES_H */
--- 260,265 ----
  extern const char *config_enum_lookup_by_value(struct config_enum * record, int val);
  extern bool config_enum_lookup_by_name(struct config_enum * record,
  						   const char *value, int *retval);
! extern struct config_generic *validate_conf_option(const char *name, char *value);
  
  #endif   /* GUC_TABLES_H */
*** /dev/null
--- b/src/test/regress/expected/persistent.out
***************
*** 0 ****
--- 1,584 ----
+ -- parameter which cannot be set after connection start.
+ set persistent log_connections=on;
+ -- parameter can only be set at during server start.
+ set persistent max_connections To 10;
+ set persistent wal_level = hot_standby;
+ -- parameter can set by the backend
+ set persistent authentication_timeout = 10;
+ set persistent vacuum_cost_delay To 200;
+ ERROR:  200 is outside the valid range for parameter "vacuum_cost_delay" (0 .. 100)
+ set persistent bgwriter_lru_multiplier = 3.2;
+ set persistent full_page_writes = off;
+ set persistent synchronous_commit To off;
+ set persistent synchronous_standby_names = 'standby1, standby2';
+ set persistent seq_page_cost = 0.9;
+ set persistent autovacuum_naptime To 30;
+ set persistent search_path = 'public';
+ set persistent default_tablespace = '';
+ set persistent checkpoint_timeout = 1;
+ ERROR:  1 is outside the valid range for parameter "checkpoint_timeout" (30 .. 3600)
+ set persistent checkpoint_timeout = 3700;
+ ERROR:  3700 is outside the valid range for parameter "checkpoint_timeout" (30 .. 3600)
+ set persistent checkpoint_timeout = 90;
+ set persistent restart_after_crash TO on;
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show wal_level;
+  wal_level 
+ -----------
+  minimal
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  1min
+ (1 row)
+ 
+ show vacuum_cost_delay;
+  vacuum_cost_delay 
+ -------------------
+  0
+ (1 row)
+ 
+ show bgwriter_lru_multiplier;
+  bgwriter_lru_multiplier 
+ -------------------------
+  2
+ (1 row)
+ 
+ show full_page_writes;
+  full_page_writes 
+ ------------------
+  on
+ (1 row)
+ 
+ show synchronous_commit;
+  synchronous_commit 
+ --------------------
+  on
+ (1 row)
+ 
+ show synchronous_standby_names;
+  synchronous_standby_names 
+ ---------------------------
+  
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  1
+ (1 row)
+ 
+ show autovacuum_naptime;
+  autovacuum_naptime 
+ --------------------
+  1min
+ (1 row)
+ 
+ show search_path;
+   search_path   
+ ----------------
+  "$user",public
+ (1 row)
+ 
+ show default_tablespace;
+  default_tablespace 
+ --------------------
+  
+ (1 row)
+ 
+ show checkpoint_timeout;
+  checkpoint_timeout 
+ --------------------
+  5min
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- reload the new configurations.
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show wal_level;
+  wal_level 
+ -----------
+  minimal
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  10s
+ (1 row)
+ 
+ show vacuum_cost_delay;
+  vacuum_cost_delay 
+ -------------------
+  0
+ (1 row)
+ 
+ show bgwriter_lru_multiplier;
+  bgwriter_lru_multiplier 
+ -------------------------
+  3.2
+ (1 row)
+ 
+ show full_page_writes;
+  full_page_writes 
+ ------------------
+  off
+ (1 row)
+ 
+ show synchronous_commit;
+  synchronous_commit 
+ --------------------
+  off
+ (1 row)
+ 
+ show synchronous_standby_names;
+  synchronous_standby_names 
+ ---------------------------
+  standby1, standby2
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show autovacuum_naptime;
+  autovacuum_naptime 
+ --------------------
+  30s
+ (1 row)
+ 
+ show search_path;
+  search_path 
+ -------------
+  public
+ (1 row)
+ 
+ show default_tablespace;
+  default_tablespace 
+ --------------------
+  
+ (1 row)
+ 
+ show checkpoint_timeout;
+  checkpoint_timeout 
+ --------------------
+  90s
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- reconnect to see the new configurations
+ \c
+ select name, setting from pg_settings where name = 'log_connections';
+       name       | setting 
+ -----------------+---------
+  log_connections | on
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'max_connections';
+       name       | setting 
+ -----------------+---------
+  max_connections | 100
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'wal_level';
+    name    | setting 
+ -----------+---------
+  wal_level | minimal
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'authentication_timeout';
+           name          | setting 
+ ------------------------+---------
+  authentication_timeout | 10
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'vacuum_cost_delay';
+        name        | setting 
+ -------------------+---------
+  vacuum_cost_delay | 0
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'bgwriter_lru_multiplier';
+           name           | setting 
+ -------------------------+---------
+  bgwriter_lru_multiplier | 3.2
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'full_page_writes';
+        name       | setting 
+ ------------------+---------
+  full_page_writes | off
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'synchronous_commit';
+         name        | setting 
+ --------------------+---------
+  synchronous_commit | off
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'synchronous_standby_names';
+            name            |      setting       
+ ---------------------------+--------------------
+  synchronous_standby_names | standby1, standby2
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'seq_page_cost';
+      name      | setting 
+ ---------------+---------
+  seq_page_cost | 0.9
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'autovacuum_naptime';
+         name        | setting 
+ --------------------+---------
+  autovacuum_naptime | 30
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'search_path';
+     name     | setting 
+ -------------+---------
+  search_path | public
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'default_tablespace';
+         name        | setting 
+ --------------------+---------
+  default_tablespace | 
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'checkpoint_timeout';
+         name        | setting 
+ --------------------+---------
+  checkpoint_timeout | 90
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'restart_after_crash';
+         name         | setting 
+ ---------------------+---------
+  restart_after_crash | on
+ (1 row)
+ 
+ -- Reset the some of the parameters which are set in above
+ set persistent log_connections = default;
+ set persistent max_connections To default;
+ set persistent authentication_timeout To default;
+ set persistent synchronous_commit = default;
+ set persistent restart_after_crash To default;
+ -- reload the new configurations.
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'log_connections';
+       name       | setting 
+ -----------------+---------
+  log_connections | on
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'max_connections';
+       name       | setting 
+ -----------------+---------
+  max_connections | 100
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'authentication_timeout';
+           name          | setting 
+ ------------------------+---------
+  authentication_timeout | 60
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'seq_page_cost';
+      name      | setting 
+ ---------------+---------
+  seq_page_cost | 0.9
+ (1 row)
+ 
+ select name, setting from pg_settings where name = 'restart_after_crash';
+         name         | setting 
+ ---------------------+---------
+  restart_after_crash | on
+ (1 row)
+ 
+ -- reconnect to see the new configurations
+ \c
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  1min
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- set the parameters again which are reset above.
+ set persistent log_connections To yes;
+ set persistent max_connections = 50;
+ set persistent authentication_timeout = 20;
+ set persistent synchronous_commit To off;
+ set persistent restart_after_crash To yes;
+ -- reload the new configurations.
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show log_connections;
+  log_connections 
+ -----------------
+  off
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  20s
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- reconnect to see the new configurations
+ \c
+ show log_connections;
+  log_connections 
+ -----------------
+  on
+ (1 row)
+ 
+ show max_connections;
+  max_connections 
+ -----------------
+  100
+ (1 row)
+ 
+ show authentication_timeout;
+  authentication_timeout 
+ ------------------------
+  20s
+ (1 row)
+ 
+ show seq_page_cost;
+  seq_page_cost 
+ ---------------
+  0.9
+ (1 row)
+ 
+ show restart_after_crash;
+  restart_after_crash 
+ ---------------------
+  on
+ (1 row)
+ 
+ -- set a configuration param inside a function
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ set persistent enable_hashagg=off;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ select persistent_func();
+  persistent_func 
+ -----------------
+                1
+ (1 row)
+ 
+ show enable_hashagg;
+  enable_hashagg 
+ ----------------
+  on
+ (1 row)
+ 
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show enable_hashagg;
+  enable_hashagg 
+ ----------------
+  off
+ (1 row)
+ 
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ set persistent enable_hashagg=default;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ select persistent_func();
+  persistent_func 
+ -----------------
+                1
+ (1 row)
+ 
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ show enable_hashagg;
+  enable_hashagg 
+ ----------------
+  on
+ (1 row)
+ 
+ Drop function persistent_func();
+ -- Reset all parameters which are set at above.
+ set persistent log_connections To default;
+ set persistent max_connections = default;
+ set persistent wal_level To default;
+ set persistent authentication_timeout To default;
+ set persistent vacuum_cost_delay = default;
+ set persistent bgwriter_lru_multiplier To default;
+ set persistent full_page_writes To default;
+ set persistent synchronous_commit = default;
+ set persistent synchronous_standby_names To default;
+ set persistent seq_page_cost To default;
+ set persistent autovacuum_naptime = default;
+ set persistent search_path To default;
+ set persistent default_tablespace To default;
+ set persistent checkpoint_timeout To default;
+ set persistent restart_after_crash = default;
+ select pg_reload_conf();
+  pg_reload_conf 
+ ----------------
+  t
+ (1 row)
+ 
+ select pg_sleep(1);
+  pg_sleep 
+ ----------
+  
+ (1 row)
+ 
+ -- Normal user tries to set
+ create user test password 'test';
+ SET SESSION AUTHORIZATION test;
+ set persistent enable_seqscan=off;
+ ERROR:  must be superuser to execute SET/RESET PERSISTENT command
+ \c -
+ drop user test;
+ -- In a transaction block tries to set
+ start transaction;
+ set persistent enable_hashagg=off;
+ ERROR:  SET/RESET PERSISTENT command cannot run inside a transaction block
+ commit;
+ start transaction;
+ set persistent enable_hashagg=default;
+ ERROR:  SET/RESET PERSISTENT command cannot run inside a transaction block
+ commit;
*** a/src/test/regress/parallel_schedule
--- b/src/test/regress/parallel_schedule
***************
*** 108,111 **** test: select_views portals_p2 foreign_key cluster dependency guc bitmapops combo
  test: plancache limit plpgsql copy2 temp domain rangefuncs prepare without_oid conversion truncate alter_table sequence polymorphism rowtypes returning largeobject with xml
  
  # run stats by itself because its delay may be insufficient under heavy load
! test: stats
--- 108,114 ----
  test: plancache limit plpgsql copy2 temp domain rangefuncs prepare without_oid conversion truncate alter_table sequence polymorphism rowtypes returning largeobject with xml
  
  # run stats by itself because its delay may be insufficient under heavy load
! test: stats 
! 
! # run persistent by itself because it modifies the configuration parameters
! test: persistent
*** a/src/test/regress/serial_schedule
--- b/src/test/regress/serial_schedule
***************
*** 135,137 **** test: largeobject
--- 135,138 ----
  test: with
  test: xml
  test: stats
+ test: persistent
*** /dev/null
--- b/src/test/regress/sql/persistent.sql
***************
*** 0 ****
--- 1,215 ----
+ -- parameter which cannot be set after connection start.
+ set persistent log_connections=on;
+ 
+ -- parameter can only be set at during server start.
+ set persistent max_connections To 10;
+ set persistent wal_level = hot_standby;
+ 
+ -- parameter can set by the backend
+ set persistent authentication_timeout = 10;
+ set persistent vacuum_cost_delay To 200;
+ set persistent bgwriter_lru_multiplier = 3.2;
+ set persistent full_page_writes = off;
+ set persistent synchronous_commit To off;
+ set persistent synchronous_standby_names = 'standby1, standby2';
+ set persistent seq_page_cost = 0.9;
+ set persistent autovacuum_naptime To 30;
+ set persistent search_path = 'public';
+ set persistent default_tablespace = '';
+ set persistent checkpoint_timeout = 1;
+ set persistent checkpoint_timeout = 3700;
+ set persistent checkpoint_timeout = 90;
+ set persistent restart_after_crash TO on;
+ 
+ 
+ show log_connections;
+ 
+ show max_connections;
+ show wal_level;
+ 
+ show authentication_timeout;
+ show vacuum_cost_delay;
+ show bgwriter_lru_multiplier;
+ show full_page_writes;
+ show synchronous_commit;
+ show synchronous_standby_names;
+ show seq_page_cost;
+ show autovacuum_naptime;
+ show search_path;
+ show default_tablespace;
+ show checkpoint_timeout;
+ show restart_after_crash;
+ 
+ -- reload the new configurations.
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show log_connections;
+ 
+ show max_connections;
+ show wal_level;
+ 
+ show authentication_timeout;
+ show vacuum_cost_delay;
+ show bgwriter_lru_multiplier;
+ show full_page_writes;
+ show synchronous_commit;
+ show synchronous_standby_names;
+ show seq_page_cost;
+ show autovacuum_naptime;
+ show search_path;
+ show default_tablespace;
+ show checkpoint_timeout;
+ show restart_after_crash;
+ 
+ 
+ -- reconnect to see the new configurations
+ \c
+ 
+ select name, setting from pg_settings where name = 'log_connections';
+ 
+ select name, setting from pg_settings where name = 'max_connections';
+ select name, setting from pg_settings where name = 'wal_level';
+ 
+ select name, setting from pg_settings where name = 'authentication_timeout';
+ select name, setting from pg_settings where name = 'vacuum_cost_delay';
+ select name, setting from pg_settings where name = 'bgwriter_lru_multiplier';
+ select name, setting from pg_settings where name = 'full_page_writes';
+ select name, setting from pg_settings where name = 'synchronous_commit';
+ select name, setting from pg_settings where name = 'synchronous_standby_names';
+ select name, setting from pg_settings where name = 'seq_page_cost';
+ select name, setting from pg_settings where name = 'autovacuum_naptime';
+ select name, setting from pg_settings where name = 'search_path';
+ select name, setting from pg_settings where name = 'default_tablespace';
+ select name, setting from pg_settings where name = 'checkpoint_timeout';
+ select name, setting from pg_settings where name = 'restart_after_crash';
+ 
+ -- Reset the some of the parameters which are set in above
+ set persistent log_connections = default;
+ 
+ set persistent max_connections To default;
+ 
+ set persistent authentication_timeout To default;
+ set persistent synchronous_commit = default;
+ set persistent restart_after_crash To default;
+ 
+ -- reload the new configurations.
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ select name, setting from pg_settings where name = 'log_connections';
+ select name, setting from pg_settings where name = 'max_connections';
+ select name, setting from pg_settings where name = 'authentication_timeout';
+ select name, setting from pg_settings where name = 'seq_page_cost';
+ select name, setting from pg_settings where name = 'restart_after_crash';
+ 
+ -- reconnect to see the new configurations
+ \c
+ 
+ show log_connections;
+ show max_connections;
+ show authentication_timeout;
+ show seq_page_cost;
+ show restart_after_crash;
+ 
+ -- set the parameters again which are reset above.
+ set persistent log_connections To yes;
+ 
+ set persistent max_connections = 50;
+ 
+ set persistent authentication_timeout = 20;
+ set persistent synchronous_commit To off;
+ set persistent restart_after_crash To yes;
+ 
+ -- reload the new configurations.
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show log_connections;
+ show max_connections;
+ show authentication_timeout;
+ show seq_page_cost;
+ show restart_after_crash;
+ 
+ -- reconnect to see the new configurations
+ \c
+ show log_connections;
+ show max_connections;
+ show authentication_timeout;
+ show seq_page_cost;
+ show restart_after_crash;
+ 
+ -- set a configuration param inside a function
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ set persistent enable_hashagg=off;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ 
+ select persistent_func();
+ 
+ show enable_hashagg;
+ 
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show enable_hashagg;
+ 
+ create or replace function persistent_func() returns integer as
+ $$
+ begin
+ set persistent enable_hashagg=default;
+ return 1;
+ end;
+ $$ Language plpgsql;
+ 
+ select persistent_func();
+ 
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ show enable_hashagg;
+ 
+ Drop function persistent_func();
+ 
+ -- Reset all parameters which are set at above.
+ set persistent log_connections To default;
+ 
+ set persistent max_connections = default;
+ set persistent wal_level To default;
+ 
+ set persistent authentication_timeout To default;
+ set persistent vacuum_cost_delay = default;
+ set persistent bgwriter_lru_multiplier To default;
+ set persistent full_page_writes To default;
+ set persistent synchronous_commit = default;
+ set persistent synchronous_standby_names To default;
+ set persistent seq_page_cost To default;
+ set persistent autovacuum_naptime = default;
+ set persistent search_path To default;
+ set persistent default_tablespace To default;
+ set persistent checkpoint_timeout To default;
+ set persistent restart_after_crash = default;
+ 
+ select pg_reload_conf();
+ select pg_sleep(1);
+ 
+ 
+ -- Normal user tries to set
+ create user test password 'test';
+ SET SESSION AUTHORIZATION test;
+ set persistent enable_seqscan=off;
+ \c -
+ drop user test;
+ 
+ -- In a transaction block tries to set
+ start transaction;
+ set persistent enable_hashagg=off;
+ commit;
+ 
+ start transaction;
+ set persistent enable_hashagg=default;
+ commit;
+