There is last version of patch with following changes/improvements:

1) I divide set_config_option to more smaller functions without backside effect.

2) Behavior of reconfiguration is "same" in SIG_HUP context (exclude elevel). All errors are reported and full validity of file is checked too.

        Zdenek


Index: src/backend/utils/misc/guc-file.l
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/utils/misc/guc-file.l,v
retrieving revision 1.37
diff -c -r1.37 guc-file.l
*** src/backend/utils/misc/guc-file.l	7 Mar 2006 01:03:12 -0000	1.37
--- src/backend/utils/misc/guc-file.l	13 Jul 2006 21:55:28 -0000
***************
*** 112,119 ****
  void
  ProcessConfigFile(GucContext context)
  {
! 	int			elevel;
  	struct name_value_pair *item, *head, *tail;
  
  	Assert(context == PGC_POSTMASTER || context == PGC_SIGHUP);
  
--- 112,120 ----
  void
  ProcessConfigFile(GucContext context)
  {
! 	int			elevel, i;
  	struct name_value_pair *item, *head, *tail;
+ 	char	   *env;
  
  	Assert(context == PGC_POSTMASTER || context == PGC_SIGHUP);
  
***************
*** 137,146 ****
  
  	/* Check if all options are valid */
  	for (item = head; item; item = item->next)
! 	{
! 		if (!set_config_option(item->name, item->value, context,
! 							   PGC_S_FILE, false, false))
  			goto cleanup_list;
  	}
  
  	/* If we got here all the options checked out okay, so apply them. */
--- 138,173 ----
  
  	/* Check if all options are valid */
  	for (item = head; item; item = item->next)
! 	{   
! 		bool isEqual, isContextOk;
! 
! 		if (!verify_config_option(item->name, item->value, context,
! 						  PGC_S_FILE, &isEqual, &isContextOk))
! 		{
! 			ereport(elevel,
! 				(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
! 				errmsg("configuration file is invalid")));
  			goto cleanup_list;
+ 		}
+ 
+ 		if( isContextOk == false )
+ 		{
+ 			if( context == PGC_SIGHUP )
+ 			{
+ 				if ( isEqual == false )
+ 				{
+ 					ereport(elevel,
+ 						(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
+ 						errmsg("parameter \"%s\" cannot be changed after server start; configuration file change ignored",
+ 						item->name)));
+ 				}
+ 			}
+ 			else 
+ 			{
+ 				// if it is boot phase loading context must be valid for all configuration item.
+ 				goto cleanup_list;
+ 			}
+ 		}
  	}
  
  	/* If we got here all the options checked out okay, so apply them. */
***************
*** 150,155 ****
--- 177,233 ----
  						  PGC_S_FILE, false, true);
  	}
  
+ 	if( context == PGC_SIGHUP)
+ 	{
+ 	/* Revert all "untouched" options with reset source PGC_S_FILE to 
+      * default/boot value. 
+      */
+ 		for (i = 0; i < num_guc_variables; i++)
+ 		{
+ 			struct config_generic *gconf = guc_variables[i];
+ 			if ( gconf->context != PGC_INTERNAL && gconf->context != PGC_POSTMASTER && 
+ 				!( gconf->context == PGC_BACKEND && IsUnderPostmaster) &&
+ 				 (gconf->reset_source == PGC_S_FILE) && ( (gconf->status & GUC_JUST_RELOAD) == 0) )
+ 			{
+ 				if( set_config_option(gconf->name, NULL, context,
+ 					  PGC_S_FILE, false, true) )
+ 				{
+ 					GucStack   *stack;
+ 					/* set correctly source */
+ 					gconf->reset_source = PGC_S_DEFAULT;
+ 					for (stack = gconf->stack; stack; stack = stack->prev)
+ 					{
+ 						if (stack->source == PGC_S_FILE)
+ 						{
+ 							stack->source = PGC_S_DEFAULT;
+ 						}
+ 					}
+ 
+ 					ereport(elevel,
+ 							(errcode(ERRCODE_SUCCESSFUL_COMPLETION),
+ 							errmsg("configuration option %s has been revert to the boot value", gconf->name)));
+ 				}
+ 			}
+ 			gconf->status &= ~GUC_JUST_RELOAD;
+ 		}
+ 
+ 		/* Revert to environment variable. PGPORT is ignored, because it cannot be 
+ 		 * set in running state. 
+ 		 */ 
+ 		env = getenv("PGDATESTYLE");
+ 		if (env != NULL)
+ 		{
+ 			set_config_option("datestyle", env, context, 
+ 							PGC_S_ENV_VAR, false, true);
+ 		}
+ 
+ 		env = getenv("PGCLIENTENCODING");
+ 		if (env != NULL)
+ 		{
+ 			set_config_option("client_encoding", env, context, 
+ 							PGC_S_ENV_VAR, false, true);
+ 		}
+ 	}
   cleanup_list:
  	free_name_value_list(head);
  }
Index: src/backend/utils/misc/guc.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/utils/misc/guc.c,v
retrieving revision 1.319
diff -c -r1.319 guc.c
*** src/backend/utils/misc/guc.c	11 May 2006 19:15:35 -0000	1.319
--- src/backend/utils/misc/guc.c	13 Jul 2006 21:55:28 -0000
***************
*** 2648,2686 ****
  					struct config_bool *conf = (struct config_bool *) gconf;
  
  					if (conf->assign_hook)
! 						if (!(*conf->assign_hook) (conf->reset_val, true,
  												   PGC_S_DEFAULT))
  							elog(FATAL, "failed to initialize %s to %d",
! 								 conf->gen.name, (int) conf->reset_val);
! 					*conf->variable = conf->reset_val;
  					break;
  				}
  			case PGC_INT:
  				{
  					struct config_int *conf = (struct config_int *) gconf;
  
! 					Assert(conf->reset_val >= conf->min);
! 					Assert(conf->reset_val <= conf->max);
  					if (conf->assign_hook)
! 						if (!(*conf->assign_hook) (conf->reset_val, true,
  												   PGC_S_DEFAULT))
  							elog(FATAL, "failed to initialize %s to %d",
! 								 conf->gen.name, conf->reset_val);
! 					*conf->variable = conf->reset_val;
  					break;
  				}
  			case PGC_REAL:
  				{
  					struct config_real *conf = (struct config_real *) gconf;
  
! 					Assert(conf->reset_val >= conf->min);
! 					Assert(conf->reset_val <= conf->max);
  					if (conf->assign_hook)
! 						if (!(*conf->assign_hook) (conf->reset_val, true,
  												   PGC_S_DEFAULT))
  							elog(FATAL, "failed to initialize %s to %g",
! 								 conf->gen.name, conf->reset_val);
! 					*conf->variable = conf->reset_val;
  					break;
  				}
  			case PGC_STRING:
--- 2648,2686 ----
  					struct config_bool *conf = (struct config_bool *) gconf;
  
  					if (conf->assign_hook)
! 						if (!(*conf->assign_hook) (conf->boot_val, true,
  												   PGC_S_DEFAULT))
  							elog(FATAL, "failed to initialize %s to %d",
! 								 conf->gen.name, (int) conf->boot_val);
! 					*conf->variable = conf->reset_val = conf->boot_val;
  					break;
  				}
  			case PGC_INT:
  				{
  					struct config_int *conf = (struct config_int *) gconf;
  
! 					Assert(conf->boot_val >= conf->min);
! 					Assert(conf->boot_val <= conf->max);
  					if (conf->assign_hook)
! 						if (!(*conf->assign_hook) (conf->boot_val, true,
  												   PGC_S_DEFAULT))
  							elog(FATAL, "failed to initialize %s to %d",
! 								 conf->gen.name, conf->boot_val);
! 					*conf->variable = conf->reset_val = conf->boot_val; 
  					break;
  				}
  			case PGC_REAL:
  				{
  					struct config_real *conf = (struct config_real *) gconf;
  
! 					Assert(conf->boot_val >= conf->min);
! 					Assert(conf->boot_val <= conf->max);
  					if (conf->assign_hook)
! 						if (!(*conf->assign_hook) (conf->boot_val, true,
  												   PGC_S_DEFAULT))
  							elog(FATAL, "failed to initialize %s to %g",
! 								 conf->gen.name, conf->boot_val);
! 					*conf->variable = conf->reset_val = conf->boot_val; 
  					break;
  				}
  			case PGC_STRING:
***************
*** 3133,3139 ****
  	for (i = 0; i < num_guc_variables; i++)
  	{
  		struct config_generic *gconf = guc_variables[i];
! 		int			my_status = gconf->status;
  		GucStack   *stack = gconf->stack;
  		bool		useTentative;
  		bool		changed;
--- 3133,3139 ----
  	for (i = 0; i < num_guc_variables; i++)
  	{
  		struct config_generic *gconf = guc_variables[i];
! 		int			my_status = gconf->status & (~GUC_JUST_RELOAD);
  		GucStack   *stack = gconf->stack;
  		bool		useTentative;
  		bool		changed;
***************
*** 3571,3630 ****
  	return result;
  }
  
- 
  /*
!  * Sets option `name' to given value. The value should be a string
!  * which is going to be parsed and converted to the appropriate data
!  * type.  The context and source parameters indicate in which context this
!  * function is being called so it can apply the access restrictions
!  * properly.
!  *
!  * If value is NULL, set the option to its default value. If the
!  * parameter changeVal is false then don't really set the option but do all
!  * the checks to see if it would work.
!  *
!  * If there is an error (non-existing option, invalid value) then an
!  * ereport(ERROR) is thrown *unless* this is called in a context where we
!  * don't want to ereport (currently, startup or SIGHUP config file reread).
!  * In that case we write a suitable error message via ereport(DEBUG) and
!  * return false. This is working around the deficiencies in the ereport
!  * mechanism, so don't blame me.  In all other cases, the function
!  * returns true, including cases where the input is valid but we chose
!  * not to apply it because of context or source-priority considerations.
!  *
!  * See also SetConfigOption for an external interface.
   */
! bool
! set_config_option(const char *name, const char *value,
! 				  GucContext context, GucSource source,
! 				  bool isLocal, bool changeVal)
  {
- 	struct config_generic *record;
- 	int			elevel;
- 	bool		makeDefault;
  
! 	if (context == PGC_SIGHUP || source == PGC_S_DEFAULT)
  	{
! 		/*
! 		 * To avoid cluttering the log, only the postmaster bleats loudly
! 		 * about problems with the config file.
! 		 */
! 		elevel = IsUnderPostmaster ? DEBUG2 : LOG;
! 	}
! 	else if (source == PGC_S_DATABASE || source == PGC_S_USER)
! 		elevel = INFO;
! 	else
! 		elevel = ERROR;
  
! 	record = find_option(name, elevel);
! 	if (record == NULL)
! 	{
! 		ereport(elevel,
! 				(errcode(ERRCODE_UNDEFINED_OBJECT),
! 			   errmsg("unrecognized configuration parameter \"%s\"", name)));
! 		return false;
  	}
  
  	/*
  	 * Check if the option can be set at this time. See guc.h for the precise
  	 * rules. Note that we don't want to throw errors if we're in the SIGHUP
--- 3571,3852 ----
  	return result;
  }
  
  /*
!  * Try to parse value. Determine what is type and call related
!  * parsing function or if newval is equal to NULL, reset value 
!  * to default or bootval. If the value parsed okay return true,
!  * else false.
   */
! static bool
! parse_value(int elevel, const struct config_generic *record, 
! 		const char *value, GucSource *source, bool changeVal, 
! 		union config_var_value *retval)
  {
  
! 	Assert( !(changeVal && retval==NULL) );
! 	/*
! 	 * Evaluate value and set variable.
! 	 */
! 	switch (record->vartype)
  	{
! 		case PGC_BOOL:
! 			{
! 				struct config_bool *conf = (struct config_bool *) record;
! 				bool		newval;
  
! 				if (value)
! 				{
! 					if (!parse_bool(value, &newval))
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 						  errmsg("parameter \"%s\" requires a Boolean value",
! 								 record->name)));
! 						return false;
! 					}
! 				}
! 				else
! 				{
! 					/* Revert value to default if source is configuration file. It is used when 
! 					 * configuration parameter is removed/commented out in the config file. Else
! 					 * RESET or SET TO DEFAULT command is called and reset_val is used. 
! 					 */
! 					if( *source == PGC_S_FILE )
! 					{
! 						newval =  conf->boot_val;
! 					}
! 					else
! 					{
! 						newval = conf->reset_val;
! 						*source = conf->gen.reset_source;
! 					}
! 				}
! 
! 				if (conf->assign_hook)
! 					if (!(*conf->assign_hook) (newval, changeVal, *source))
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 							 errmsg("invalid value for parameter \"%s\": %d",
! 									record->name, (int) newval)));
! 						return false;
! 					}
! 				if( retval != NULL )
! 					retval->boolval = newval;
! 				break;
! 			}
! 
! 		case PGC_INT:
! 			{
! 				struct config_int *conf = (struct config_int *) record;
! 				int			newval;
! 
! 				if (value)
! 				{
! 					if (!parse_int(value, &newval))
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 						 errmsg("parameter \"%s\" requires an integer value",
! 								record->name)));
! 						return false;
! 					}
! 					if (newval < conf->min || newval > conf->max)
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 								 errmsg("%d is outside the valid range for parameter \"%s\" (%d .. %d)",
! 										newval, record->name, conf->min, conf->max)));
! 						return false;
! 					}
! 				}
! 				else
! 				{
! 					/* Revert value to default if source is configuration file. It is used when 
! 					 * configuration parameter is removed/commented out in the config file. Else
! 					 * RESET or SET TO DEFAULT command is called and reset_val is used. 
! 					 */
! 					if( *source == PGC_S_FILE )
! 					{
! 						newval =  conf->boot_val;
! 					}
! 					else
! 					{
! 						newval = conf->reset_val;
! 						*source = conf->gen.reset_source;
! 					}
! 				}
! 
! 				if (conf->assign_hook)
! 					if (!(*conf->assign_hook) (newval, changeVal, *source))
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 							 errmsg("invalid value for parameter \"%s\": %d",
! 									record->name, newval)));
! 						return false;
! 					}
! 				if( retval != NULL )
! 					retval->intval = newval;
! 				break;
! 			}
! 
! 		case PGC_REAL:
! 			{
! 				struct config_real *conf = (struct config_real *) record;
! 				double		newval;
! 
! 				if (value)
! 				{
! 					if (!parse_real(value, &newval))
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 						  errmsg("parameter \"%s\" requires a numeric value",
! 								 record->name)));
! 						return false;
! 					}
! 					if (newval < conf->min || newval > conf->max)
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 								 errmsg("%g is outside the valid range for parameter \"%s\" (%g .. %g)",
! 										newval, record->name, conf->min, conf->max)));
! 						return false;
! 					}
! 				}
! 				else
! 				{
! 					/* Revert value to default if source is configuration file. It is used when 
! 					 * configuration parameter is removed/commented out in the config file. Else
! 					 * RESET or SET TO DEFAULT command is called and reset_val is used. 
! 					 */
! 					if( *source == PGC_S_FILE )
! 					{
! 						newval =  conf->boot_val;
! 					}
! 					else
! 					{
! 						newval = conf->reset_val;
! 						*source = conf->gen.reset_source;
! 					}
! 				}
! 
! 				if (conf->assign_hook)
! 					if (!(*conf->assign_hook) (newval, changeVal, *source))
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 							 errmsg("invalid value for parameter \"%s\": %g",
! 									record->name, newval)));
! 						return false;
! 					}
! 				if( retval != NULL )
! 					retval->realval = newval;
! 				break;
! 			}
! 
! 		case PGC_STRING:
! 			{
! 				struct config_string *conf = (struct config_string *) record;
! 				char	   *newval;
! 
! 				if (value)
! 				{
! 					newval = guc_strdup(elevel, value);
! 					if (newval == NULL)
! 						return false;
! 					/*
! 					 * The only sort of "parsing" check we need to do is
! 					 * apply truncation if GUC_IS_NAME.
! 					 */
! 					if (conf->gen.flags & GUC_IS_NAME)
! 						truncate_identifier(newval, strlen(newval), true);
! 				}
! 				else if (*source == PGC_S_FILE)
! 				{
! 					/* Revert value to default when item is removed from config file. */
! 					if ( conf->boot_val != NULL )
! 					{
! 						newval = guc_strdup(elevel, conf->boot_val);
! 						if (newval == NULL)
! 							return false;
! 					}
! 					else
! 					{
! 						return false;
! 					}
! 				} 
! 				else if (conf->reset_val)
! 				{
! 					/*
! 					 * We could possibly avoid strdup here, but easier to make
! 					 * this case work the same as the normal assignment case.
! 					 */
! 					newval = guc_strdup(elevel, conf->reset_val);
! 					if (newval == NULL)
! 						return false;
! 					*source = conf->gen.reset_source;
! 				}
! 				else
! 				{
! 					/* Nothing to reset to, as yet; so do nothing */
! 					break;
! 				}
! 
! 				if (conf->assign_hook)
! 				{
! 					const char *hookresult;
! 
! 					/*
! 					 * If the hook ereports, we have to make sure we free
! 					 * newval, else it will be a permanent memory leak.
! 					 */
! 					hookresult = call_string_assign_hook(conf->assign_hook,
! 														 newval,
! 														 changeVal,
! 														 *source);
! 					if (hookresult == NULL)
! 					{
! 						free(newval);
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 						 errmsg("invalid value for parameter \"%s\": \"%s\"",
! 								record->name, value ? value : "")));
! 						return false;
! 					}
! 					else if (hookresult != newval)
! 					{
! 						free(newval);
! 
! 						/*
! 						 * Having to cast away const here is annoying, but the
! 						 * alternative is to declare assign_hooks as returning
! 						 * char*, which would mean they'd have to cast away
! 						 * const, or as both taking and returning char*, which
! 						 * doesn't seem attractive either --- we don't want
! 						 * them to scribble on the passed str.
! 						 */
! 						newval = (char *) hookresult;
! 					}
! 				}
! 
! 				if ( !changeVal )
! 					free(newval);
! 				if( retval != NULL )
! 					retval->stringval= newval;
! 				break;
! 			}
  	}
+ 	return true;
+ }
  
+ /*
+  *
+  */
+ bool
+ checkContext(int elevel, struct config_generic *record, GucContext context)
+ {
  	/*
  	 * Check if the option can be set at this time. See guc.h for the precise
  	 * rules. Note that we don't want to throw errors if we're in the SIGHUP
***************
*** 3633,3666 ****
  	switch (record->context)
  	{
  		case PGC_INTERNAL:
- 			if (context == PGC_SIGHUP)
- 				return true;
  			if (context != PGC_INTERNAL)
  			{
  				ereport(elevel,
  						(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  						 errmsg("parameter \"%s\" cannot be changed",
! 								name)));
  				return false;
  			}
  			break;
  		case PGC_POSTMASTER:
  			if (context == PGC_SIGHUP)
! 			{
! 				if (changeVal && !is_newvalue_equal(record, value))
! 					ereport(elevel,
! 							(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
! 							 errmsg("parameter \"%s\" cannot be changed after server start; configuration file change ignored",
! 									name)));
  
- 				return true;
- 			}
  			if (context != PGC_POSTMASTER)
  			{
  				ereport(elevel,
  						(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  						 errmsg("parameter \"%s\" cannot be changed after server start",
! 								name)));
  				return false;
  			}
  			break;
--- 3855,3879 ----
  	switch (record->context)
  	{
  		case PGC_INTERNAL:
  			if (context != PGC_INTERNAL)
  			{
  				ereport(elevel,
  						(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  						 errmsg("parameter \"%s\" cannot be changed",
! 								record->name)));
  				return false;
  			}
  			break;
  		case PGC_POSTMASTER:
  			if (context == PGC_SIGHUP)
! 				return false;
  
  			if (context != PGC_POSTMASTER)
  			{
  				ereport(elevel,
  						(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  						 errmsg("parameter \"%s\" cannot be changed after server start",
! 								record->name)));
  				return false;
  			}
  			break;
***************
*** 3670,3676 ****
  				ereport(elevel,
  						(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  						 errmsg("parameter \"%s\" cannot be changed now",
! 								name)));
  				return false;
  			}
  
--- 3883,3889 ----
  				ereport(elevel,
  						(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  						 errmsg("parameter \"%s\" cannot be changed now",
! 								record->name)));
  				return false;
  			}
  
***************
*** 3693,3706 ****
  				 * backend start.
  				 */
  				if (IsUnderPostmaster)
! 					return true;
  			}
  			else if (context != PGC_BACKEND && context != PGC_POSTMASTER)
  			{
  				ereport(elevel,
  						(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  						 errmsg("parameter \"%s\" cannot be set after connection start",
! 								name)));
  				return false;
  			}
  			break;
--- 3906,3921 ----
  				 * backend start.
  				 */
  				if (IsUnderPostmaster)
! 				{
! 					return false;
! 				}
  			}
  			else if (context != PGC_BACKEND && context != PGC_POSTMASTER)
  			{
  				ereport(elevel,
  						(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
  						 errmsg("parameter \"%s\" cannot be set after connection start",
! 								record->name)));
  				return false;
  			}
  			break;
***************
*** 3710,3716 ****
  				ereport(elevel,
  						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  						 errmsg("permission denied to set parameter \"%s\"",
! 								name)));
  				return false;
  			}
  			break;
--- 3925,3931 ----
  				ereport(elevel,
  						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
  						 errmsg("permission denied to set parameter \"%s\"",
! 								record->name)));
  				return false;
  			}
  			break;
***************
*** 3718,3729 ****
  			/* always okay */
  			break;
  	}
  
  	/*
  	 * Should we set reset/stacked values?	(If so, the behavior is not
  	 * transactional.)
  	 */
! 	makeDefault = changeVal && (source <= PGC_S_OVERRIDE) && (value != NULL);
  
  	/*
  	 * Ignore attempted set if overridden by previously processed setting.
--- 3933,4052 ----
  			/* always okay */
  			break;
  	}
+ 	return true;
+ }
+ /*
+  * Get error level for different sources and context.
+  */
+ int
+ get_elevel(GucContext context, GucSource source)
+ {
+ 	int elevel;
+ 	if (context == PGC_SIGHUP || source == PGC_S_DEFAULT)
+ 	{
+ 		/*
+ 		 * To avoid cluttering the log, only the postmaster bleats loudly
+ 		 * about problems with the config file.
+ 		 */
+ 		elevel = IsUnderPostmaster ? DEBUG2 : LOG;
+ 	}
+ 	else if (source == PGC_S_DATABASE || source == PGC_S_USER)
+ 		elevel = INFO;
+ 	else
+ 		elevel = ERROR;
+ 
+ 	return elevel;
+ }
+ 
+ /*
+  * Verify if option exists and value is valid.
+  * It is primary used for validation of items in configuration file.
+  */
+ bool
+ verify_config_option(const char *name, const char *value,
+ 				GucContext context, GucSource source,
+ 				bool *isNewEqual, bool *isContextOK)
+ {
+ 	union config_var_value newval;
+ 	int			elevel;
+ 	struct config_generic *record;
+ 
+ 	elevel = get_elevel(context, source);
+ 
+ 	record = find_option(name, elevel);
+ 	if (record == NULL)
+ 	{
+ 		ereport(elevel,
+ 				(errcode(ERRCODE_UNDEFINED_OBJECT),
+ 			   errmsg("unrecognized configuration parameter \"%s\"", name)));
+ 		return false;
+ 	}
+ 
+ 	if( parse_value(elevel, record, value, &source, false,  &newval) )
+ 	{	
+ 		if( isNewEqual != NULL) *isNewEqual = is_newvalue_equal(record, value);
+ 		if( isContextOK != NULL) *isContextOK = checkContext(elevel, record, context);
+ 	}
+ 	else 
+ 		return false;
+ 
+     return true;
+ }
+ 				 
+ 
+ /*
+  * Sets option `name' to given value. The value should be a string
+  * which is going to be parsed and converted to the appropriate data
+  * type.  The context and source parameters indicate in which context this
+  * function is being called so it can apply the access restrictions
+  * properly.
+  *
+  * If value is NULL, set the option to its default value. If the
+  * parameter changeVal is false then don't really set the option but do all
+  * the checks to see if it would work.
+  *
+  * If there is an error (non-existing option, invalid value) then an
+  * ereport(ERROR) is thrown *unless* this is called in a context where we
+  * don't want to ereport (currently, startup or SIGHUP config file reread).
+  * In that case we write a suitable error message via ereport(DEBUG) and
+  * return false. This is working around the deficiencies in the ereport
+  * mechanism, so don't blame me.  In all other cases, the function
+  * returns true, including cases where the input is valid but we chose
+  * not to apply it because of context or source-priority considerations.
+  *
+  * See also SetConfigOption for an external interface.
+  */
+ bool
+ set_config_option(const char *name, const char *value,
+ 				  GucContext context, GucSource source,
+ 				  bool isLocal, bool changeVal)
+ {
+ 	struct config_generic *record;
+ 	int			elevel;
+ 	bool		makeDefault;
+ 
+ 	elevel = get_elevel(context, source);
+ 
+ 	record = find_option(name, elevel);
+ 	if (record == NULL)
+ 	{
+ 		ereport(elevel,
+ 				(errcode(ERRCODE_UNDEFINED_OBJECT),
+ 			   errmsg("unrecognized configuration parameter \"%s\"", name)));
+ 		return false;
+ 	}
+ 	
+ 	/* Check if change is allowed in the running context. */
+     if( !checkContext ) 
+ 	{
+ 		return false;
+ 	}
  
  	/*
  	 * Should we set reset/stacked values?	(If so, the behavior is not
  	 * transactional.)
  	 */
! 	makeDefault = changeVal && (source <= PGC_S_OVERRIDE) && (value != NULL || source == PGC_S_FILE);
  
  	/*
  	 * Ignore attempted set if overridden by previously processed setting.
***************
*** 3752,3784 ****
  			{
  				struct config_bool *conf = (struct config_bool *) record;
  				bool		newval;
! 
! 				if (value)
! 				{
! 					if (!parse_bool(value, &newval))
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 						  errmsg("parameter \"%s\" requires a Boolean value",
! 								 name)));
! 						return false;
! 					}
! 				}
! 				else
! 				{
! 					newval = conf->reset_val;
! 					source = conf->gen.reset_source;
! 				}
! 
! 				if (conf->assign_hook)
! 					if (!(*conf->assign_hook) (newval, changeVal, source))
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 							 errmsg("invalid value for parameter \"%s\": %d",
! 									name, (int) newval)));
! 						return false;
! 					}
  
  				if (changeVal || makeDefault)
  				{
--- 4075,4083 ----
  			{
  				struct config_bool *conf = (struct config_bool *) record;
  				bool		newval;
! 				
! 				if( !parse_value(elevel, record, value, &source, changeVal, (union config_var_value*) &newval) )
! 					return false; 
  
  				if (changeVal || makeDefault)
  				{
***************
*** 3829,3868 ****
  				struct config_int *conf = (struct config_int *) record;
  				int			newval;
  
! 				if (value)
! 				{
! 					if (!parse_int(value, &newval))
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 						 errmsg("parameter \"%s\" requires an integer value",
! 								name)));
! 						return false;
! 					}
! 					if (newval < conf->min || newval > conf->max)
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 								 errmsg("%d is outside the valid range for parameter \"%s\" (%d .. %d)",
! 										newval, name, conf->min, conf->max)));
! 						return false;
! 					}
! 				}
! 				else
! 				{
! 					newval = conf->reset_val;
! 					source = conf->gen.reset_source;
! 				}
! 
! 				if (conf->assign_hook)
! 					if (!(*conf->assign_hook) (newval, changeVal, source))
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 							 errmsg("invalid value for parameter \"%s\": %d",
! 									name, newval)));
! 						return false;
! 					}
  
  				if (changeVal || makeDefault)
  				{
--- 4128,4135 ----
  				struct config_int *conf = (struct config_int *) record;
  				int			newval;
  
! 				if( !parse_value(elevel, record, value, &source, changeVal, (union config_var_value*) &newval) )
! 					return false;
  
  				if (changeVal || makeDefault)
  				{
***************
*** 3913,3952 ****
  				struct config_real *conf = (struct config_real *) record;
  				double		newval;
  
! 				if (value)
! 				{
! 					if (!parse_real(value, &newval))
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 						  errmsg("parameter \"%s\" requires a numeric value",
! 								 name)));
! 						return false;
! 					}
! 					if (newval < conf->min || newval > conf->max)
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 								 errmsg("%g is outside the valid range for parameter \"%s\" (%g .. %g)",
! 										newval, name, conf->min, conf->max)));
! 						return false;
! 					}
! 				}
! 				else
! 				{
! 					newval = conf->reset_val;
! 					source = conf->gen.reset_source;
! 				}
! 
! 				if (conf->assign_hook)
! 					if (!(*conf->assign_hook) (newval, changeVal, source))
! 					{
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 							 errmsg("invalid value for parameter \"%s\": %g",
! 									name, newval)));
! 						return false;
! 					}
  
  				if (changeVal || makeDefault)
  				{
--- 4180,4187 ----
  				struct config_real *conf = (struct config_real *) record;
  				double		newval;
  
! 				if( !parse_value(elevel, record, value, &source, changeVal, (union config_var_value*) &newval) )
! 					return false; 
  
  				if (changeVal || makeDefault)
  				{
***************
*** 3997,4067 ****
  				struct config_string *conf = (struct config_string *) record;
  				char	   *newval;
  
! 				if (value)
! 				{
! 					newval = guc_strdup(elevel, value);
! 					if (newval == NULL)
! 						return false;
! 					/*
! 					 * The only sort of "parsing" check we need to do is
! 					 * apply truncation if GUC_IS_NAME.
! 					 */
! 					if (conf->gen.flags & GUC_IS_NAME)
! 						truncate_identifier(newval, strlen(newval), true);
! 				}
! 				else if (conf->reset_val)
! 				{
! 					/*
! 					 * We could possibly avoid strdup here, but easier to make
! 					 * this case work the same as the normal assignment case.
! 					 */
! 					newval = guc_strdup(elevel, conf->reset_val);
! 					if (newval == NULL)
! 						return false;
! 					source = conf->gen.reset_source;
! 				}
! 				else
! 				{
! 					/* Nothing to reset to, as yet; so do nothing */
! 					break;
! 				}
! 
! 				if (conf->assign_hook)
! 				{
! 					const char *hookresult;
! 
! 					/*
! 					 * If the hook ereports, we have to make sure we free
! 					 * newval, else it will be a permanent memory leak.
! 					 */
! 					hookresult = call_string_assign_hook(conf->assign_hook,
! 														 newval,
! 														 changeVal,
! 														 source);
! 					if (hookresult == NULL)
! 					{
! 						free(newval);
! 						ereport(elevel,
! 								(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
! 						 errmsg("invalid value for parameter \"%s\": \"%s\"",
! 								name, value ? value : "")));
! 						return false;
! 					}
! 					else if (hookresult != newval)
! 					{
! 						free(newval);
! 
! 						/*
! 						 * Having to cast away const here is annoying, but the
! 						 * alternative is to declare assign_hooks as returning
! 						 * char*, which would mean they'd have to cast away
! 						 * const, or as both taking and returning char*, which
! 						 * doesn't seem attractive either --- we don't want
! 						 * them to scribble on the passed str.
! 						 */
! 						newval = (char *) hookresult;
! 					}
! 				}
  
  				if (changeVal || makeDefault)
  				{
--- 4232,4239 ----
  				struct config_string *conf = (struct config_string *) record;
  				char	   *newval;
  
! 				if( !parse_value(elevel, record, value, &source, changeVal, (union config_var_value*) &newval) )
! 					return false; 
  
  				if (changeVal || makeDefault)
  				{
***************
*** 4109,4115 ****
  					}
  				}
  				else
! 					free(newval);
  				break;
  			}
  	}
--- 4281,4288 ----
  					}
  				}
  				else
! 					if( newval != NULL )
! 						free(newval);
  				break;
  			}
  	}
***************
*** 4117,4122 ****
--- 4290,4298 ----
  	if (changeVal && (record->flags & GUC_REPORT))
  		ReportGUCOption(record);
  
+ 	if(changeVal && record->source == PGC_S_FILE && value != NULL)
+ 		record->status |= GUC_JUST_RELOAD;
+ 
  	return true;
  }
  
***************
*** 5111,5116 ****
--- 5287,5297 ----
  static bool
  is_newvalue_equal(struct config_generic *record, const char *newvalue)
  {
+ 	if( !newvalue )
+ 	{
+ 		return false;
+ 	}
+   
  	switch (record->vartype)
  	{
  		case PGC_BOOL:
Index: src/include/utils/guc.h
===================================================================
RCS file: /projects/cvsroot/pgsql/src/include/utils/guc.h,v
retrieving revision 1.68
diff -c -r1.68 guc.h
*** src/include/utils/guc.h	11 May 2006 19:15:35 -0000	1.68
--- src/include/utils/guc.h	13 Jul 2006 21:55:29 -0000
***************
*** 17,23 ****
  #include "tcop/dest.h"
  #include "utils/array.h"
  
- 
  /*
   * Certain options can only be set at certain times. The rules are
   * like this:
--- 17,22 ----
***************
*** 195,200 ****
--- 194,202 ----
  extern bool set_config_option(const char *name, const char *value,
  				  GucContext context, GucSource source,
  				  bool isLocal, bool changeVal);
+ extern bool verify_config_option(const char *name, const char *value,
+ 				GucContext context, GucSource source,
+ 				bool *isNewEqual, bool *isContextOK);
  extern char *GetConfigOptionByName(const char *name, const char **varname);
  extern void GetConfigOptionByNum(int varnum, const char **values, bool *noshow);
  extern int	GetNumConfigOptions(void);
Index: src/include/utils/guc_tables.h
===================================================================
RCS file: /projects/cvsroot/pgsql/src/include/utils/guc_tables.h,v
retrieving revision 1.22
diff -c -r1.22 guc_tables.h
*** src/include/utils/guc_tables.h	5 Mar 2006 15:59:07 -0000	1.22
--- src/include/utils/guc_tables.h	13 Jul 2006 21:55:29 -0000
***************
*** 132,138 ****
  #define GUC_HAVE_TENTATIVE	0x0001		/* tentative value is defined */
  #define GUC_HAVE_LOCAL		0x0002		/* a SET LOCAL has been executed */
  #define GUC_HAVE_STACK		0x0004		/* we have stacked prior value(s) */
! 
  
  /* GUC records for specific variable types */
  
--- 132,138 ----
  #define GUC_HAVE_TENTATIVE	0x0001		/* tentative value is defined */
  #define GUC_HAVE_LOCAL		0x0002		/* a SET LOCAL has been executed */
  #define GUC_HAVE_STACK		0x0004		/* we have stacked prior value(s) */
! #define GUC_JUST_RELOAD     0x0008      /* value is just reload from configuration file */
  
  /* GUC records for specific variable types */
  
***************
*** 142,152 ****
  	/* these fields must be set correctly in initial value: */
  	/* (all but reset_val are constants) */
  	bool	   *variable;
! 	bool		reset_val;
  	GucBoolAssignHook assign_hook;
  	GucShowHook show_hook;
  	/* variable fields, initialized at runtime: */
  	bool		tentative_val;
  };
  
  struct config_int
--- 142,153 ----
  	/* these fields must be set correctly in initial value: */
  	/* (all but reset_val are constants) */
  	bool	   *variable;
! 	bool		boot_val;
  	GucBoolAssignHook assign_hook;
  	GucShowHook show_hook;
  	/* variable fields, initialized at runtime: */
  	bool		tentative_val;
+ 	bool		reset_val;
  };
  
  struct config_int
***************
*** 155,167 ****
  	/* these fields must be set correctly in initial value: */
  	/* (all but reset_val are constants) */
  	int		   *variable;
! 	int			reset_val;
  	int			min;
  	int			max;
  	GucIntAssignHook assign_hook;
  	GucShowHook show_hook;
  	/* variable fields, initialized at runtime: */
  	int			tentative_val;
  };
  
  struct config_real
--- 156,169 ----
  	/* these fields must be set correctly in initial value: */
  	/* (all but reset_val are constants) */
  	int		   *variable;
! 	int			boot_val;
  	int			min;
  	int			max;
  	GucIntAssignHook assign_hook;
  	GucShowHook show_hook;
  	/* variable fields, initialized at runtime: */
  	int			tentative_val;
+ 	int			reset_val;
  };
  
  struct config_real
***************
*** 170,182 ****
  	/* these fields must be set correctly in initial value: */
  	/* (all but reset_val are constants) */
  	double	   *variable;
! 	double		reset_val;
  	double		min;
  	double		max;
  	GucRealAssignHook assign_hook;
  	GucShowHook show_hook;
  	/* variable fields, initialized at runtime: */
  	double		tentative_val;
  };
  
  struct config_string
--- 172,186 ----
  	/* these fields must be set correctly in initial value: */
  	/* (all but reset_val are constants) */
  	double	   *variable;
! 	double		boot_val;
  	double		min;
  	double		max;
  	GucRealAssignHook assign_hook;
  	GucShowHook show_hook;
  	/* variable fields, initialized at runtime: */
  	double		tentative_val;
+   	double		reset_val;
+  
  };
  
  struct config_string

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