/*--------------------------------------------------------------------
 * guc.c
 *
 * Support for grand unified configuration scheme, including SET
 * command, configuration file, and command line options.
 * See src/backend/utils/misc/README for more information.
 *
 * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.70 2002/06/16 00:09:12 momjian Exp $
 *
 * Copyright 2000 by PostgreSQL Global Development Group
 * Written by Peter Eisentraut <peter_e@gmx.net>.
 *--------------------------------------------------------------------
 */

#include "postgres.h"

#include <errno.h>
#include <float.h>
#include <limits.h>
#include <unistd.h>

#include "utils/guc.h"

#include "access/xlog.h"
#include "catalog/namespace.h"
#include "commands/async.h"
#include "commands/variable.h"
#include "fmgr.h"
#include "libpq/auth.h"
#include "libpq/pqcomm.h"
#include "miscadmin.h"
#include "optimizer/cost.h"
#include "optimizer/geqo.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "parser/parse_expr.h"
#include "storage/fd.h"
#include "storage/freespace.h"
#include "storage/lock.h"
#include "storage/proc.h"
#include "tcop/tcopprot.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/datetime.h"
#include "utils/elog.h"
#include "utils/pg_locale.h"
#include "pgstat.h"


/* XXX these should be in other modules' header files */
extern bool Log_connections;
extern int	PreAuthDelay;
extern int	AuthenticationTimeout;
extern int	CheckPointTimeout;
extern int	CommitDelay;
extern int	CommitSiblings;
extern bool FixBTree;

#ifdef HAVE_SYSLOG
extern char *Syslog_facility;
extern char *Syslog_ident;

static const char *assign_facility(const char *facility,
								   bool doit, bool interactive);
#endif

/*
 * Debugging options
 */
#ifdef USE_ASSERT_CHECKING
bool		assert_enabled = true;
#endif
bool		Debug_print_query = false;
bool		Debug_print_plan = false;
bool		Debug_print_parse = false;
bool		Debug_print_rewritten = false;
bool		Debug_pretty_print = false;

bool		Show_parser_stats = false;
bool		Show_planner_stats = false;
bool		Show_executor_stats = false;
bool		Show_query_stats = false;	/* this is sort of all three above
										 * together */
bool		Show_btree_build_stats = false;

bool		Explain_pretty_print = true;

bool		SQL_inheritance = true;

bool		Australian_timezones = false;

bool		Password_encryption = false;

#ifndef PG_KRB_SRVTAB
#define PG_KRB_SRVTAB ""
#endif

/*
 * These variables are all dummies that don't do anything, except in some
 * cases provide the value for SHOW to display.  The real state is elsewhere
 * and is kept in sync by assign_hooks.
 */
static double phony_random_seed;
static char *client_encoding_string;
static char *datestyle_string;
static char *default_iso_level_string;
static char *server_encoding_string;
static char *session_authorization_string;
static char *timezone_string;
static char *XactIsoLevel_string;

static const char *assign_defaultxactisolevel(const char *newval,
											  bool doit, bool interactive);


/*
 * Declarations for GUC tables
 *
 * See src/backend/utils/misc/README for design notes.
 */
enum config_type
{
	PGC_BOOL,
	PGC_INT,
	PGC_REAL,
	PGC_STRING
};

/* Generic fields applicable to all types of variables */
struct config_generic
{
	/* constant fields, must be set correctly in initial value: */
	const char *name;			/* name of variable - MUST BE FIRST */
	GucContext	context;		/* context required to set the variable */
	int			flags;			/* flag bits, see below */
	/* variable fields, initialized at runtime: */
	enum config_type vartype;	/* type of variable (set only at startup) */
	int			status;			/* status bits, see below */
	GucSource	reset_source;	/* source of the reset_value */
	GucSource	session_source;	/* source of the session_value */
	GucSource	tentative_source; /* source of the tentative_value */
	GucSource	source;			/* source of the current actual value */
};

/* bit values in flags field */
#define GUC_LIST_INPUT		0x0001	/* input can be list format */
#define GUC_LIST_QUOTE		0x0002	/* double-quote list elements */
#define GUC_NO_SHOW_ALL		0x0004	/* exclude from SHOW ALL */
#define GUC_NO_RESET_ALL	0x0008	/* exclude from RESET ALL */

/* bit values in status field */
#define GUC_HAVE_TENTATIVE	0x0001	/* tentative value is defined */
#define GUC_HAVE_LOCAL		0x0002	/* a SET LOCAL has been executed */


/* GUC records for specific variable types */

struct config_bool
{
	struct config_generic gen;
	/* these fields must be set correctly in initial value: */
	/* (all but reset_val are constants) */
	bool	   *variable;
	bool		reset_val;
	bool		(*assign_hook) (bool newval, bool doit, bool interactive);
	const char *(*show_hook) (void);
	/* variable fields, initialized at runtime: */
	bool		session_val;
	bool		tentative_val;
};

struct config_int
{
	struct config_generic gen;
	/* these fields must be set correctly in initial value: */
	/* (all but reset_val are constants) */
	int		   *variable;
	int			reset_val;
	int			min;
	int			max;
	bool		(*assign_hook) (int newval, bool doit, bool interactive);
	const char *(*show_hook) (void);
	/* variable fields, initialized at runtime: */
	int			session_val;
	int			tentative_val;
};

struct config_real
{
	struct config_generic gen;
	/* these fields must be set correctly in initial value: */
	/* (all but reset_val are constants) */
	double	   *variable;
	double		reset_val;
	double		min;
	double		max;
	bool		(*assign_hook) (double newval, bool doit, bool interactive);
	const char *(*show_hook) (void);
	/* variable fields, initialized at runtime: */
	double		session_val;
	double		tentative_val;
};

struct config_string
{
	struct config_generic gen;
	/* these fields must be set correctly in initial value: */
	/* (all are constants) */
	char	  **variable;
	const char *boot_val;
	const char *(*assign_hook) (const char *newval, bool doit, bool interactive);
	const char *(*show_hook) (void);
	/* variable fields, initialized at runtime: */
	char	   *reset_val;
	char	   *session_val;
	char	   *tentative_val;
};

/* Macros for freeing malloc'd pointers only if appropriate to do so */
/* Some of these tests are probably redundant, but be safe ... */
#define SET_STRING_VARIABLE(rec, newval) \
	do { \
		if (*(rec)->variable && \
			*(rec)->variable != (rec)->reset_val && \
			*(rec)->variable != (rec)->session_val && \
			*(rec)->variable != (rec)->tentative_val) \
			free(*(rec)->variable); \
		*(rec)->variable = (newval); \
	} while (0)
#define SET_STRING_RESET_VAL(rec, newval) \
	do { \
		if ((rec)->reset_val && \
			(rec)->reset_val != *(rec)->variable && \
			(rec)->reset_val != (rec)->session_val && \
			(rec)->reset_val != (rec)->tentative_val) \
			free((rec)->reset_val); \
		(rec)->reset_val = (newval); \
	} while (0)
#define SET_STRING_SESSION_VAL(rec, newval) \
	do { \
		if ((rec)->session_val && \
			(rec)->session_val != *(rec)->variable && \
			(rec)->session_val != (rec)->reset_val && \
			(rec)->session_val != (rec)->tentative_val) \
			free((rec)->session_val); \
		(rec)->session_val = (newval); \
	} while (0)
#define SET_STRING_TENTATIVE_VAL(rec, newval) \
	do { \
		if ((rec)->tentative_val && \
			(rec)->tentative_val != *(rec)->variable && \
			(rec)->tentative_val != (rec)->reset_val && \
			(rec)->tentative_val != (rec)->session_val) \
			free((rec)->tentative_val); \
		(rec)->tentative_val = (newval); \
	} while (0)



/*
 * TO ADD AN OPTION:
 *
 * 1. Declare a global variable of type bool, int, double, or char*
 * and make use of it.
 *
 * 2. Decide at what times it's safe to set the option. See guc.h for
 * details.
 *
 * 3. Decide on a name, a default value, upper and lower bounds (if
 * applicable), etc.
 *
 * 4. Add a record below.
 *
 * 5. Add it to src/backend/utils/misc/postgresql.conf.sample.
 *
 * 6. Add it to src/bin/psql/tab-complete.c, if it's a USERSET option.
 *
 * 7. Don't forget to document the option.
 */


/******** option records follow ********/

static struct config_bool
			ConfigureNamesBool[] =
{
	{
		{ "enable_seqscan", PGC_USERSET }, &enable_seqscan,
		true, NULL, NULL
	},
	{
		{ "enable_indexscan", PGC_USERSET }, &enable_indexscan,
		true, NULL, NULL
	},
	{
		{ "enable_tidscan", PGC_USERSET }, &enable_tidscan,
		true, NULL, NULL
	},
	{
		{ "enable_sort", PGC_USERSET }, &enable_sort,
		true, NULL, NULL
	},
	{
		{ "enable_nestloop", PGC_USERSET }, &enable_nestloop,
		true, NULL, NULL
	},
	{
		{ "enable_mergejoin", PGC_USERSET }, &enable_mergejoin,
		true, NULL, NULL
	},
	{
		{ "enable_hashjoin", PGC_USERSET }, &enable_hashjoin,
		true, NULL, NULL
	},
	{
		{ "geqo", PGC_USERSET }, &enable_geqo,
		true, NULL, NULL
	},

	{
		{ "tcpip_socket", PGC_POSTMASTER }, &NetServer,
		false, NULL, NULL
	},
	{
		{ "ssl", PGC_POSTMASTER }, &EnableSSL,
		false, NULL, NULL
	},
	{
		{ "fsync", PGC_SIGHUP }, &enableFsync,
		true, NULL, NULL
	},
	{
		{ "silent_mode", PGC_POSTMASTER }, &SilentMode,
		false, NULL, NULL
	},

	{
		{ "log_connections", PGC_BACKEND }, &Log_connections,
		false, NULL, NULL
	},
	{
		{ "log_timestamp", PGC_SIGHUP }, &Log_timestamp,
		false, NULL, NULL
	},
	{
		{ "log_pid", PGC_SIGHUP }, &Log_pid,
		false, NULL, NULL
	},

#ifdef USE_ASSERT_CHECKING
	{
		{ "debug_assertions", PGC_USERSET }, &assert_enabled,
		true, NULL, NULL
	},
#endif

	{
		{ "debug_print_query", PGC_USERSET }, &Debug_print_query,
		false, NULL, NULL
	},
	{
		{ "debug_print_parse", PGC_USERSET }, &Debug_print_parse,
		false, NULL, NULL
	},
	{
		{ "debug_print_rewritten", PGC_USERSET }, &Debug_print_rewritten,
		false, NULL, NULL
	},
	{
		{ "debug_print_plan", PGC_USERSET }, &Debug_print_plan,
		false, NULL, NULL
	},
	{
		{ "debug_pretty_print", PGC_USERSET }, &Debug_pretty_print,
		false, NULL, NULL
	},

	{
		{ "show_parser_stats", PGC_USERSET }, &Show_parser_stats,
		false, NULL, NULL
	},
	{
		{ "show_planner_stats", PGC_USERSET }, &Show_planner_stats,
		false, NULL, NULL
	},
	{
		{ "show_executor_stats", PGC_USERSET }, &Show_executor_stats,
		false, NULL, NULL
	},
	{
		{ "show_query_stats", PGC_USERSET }, &Show_query_stats,
		false, NULL, NULL
	},
#ifdef BTREE_BUILD_STATS
	{
		{ "show_btree_build_stats", PGC_SUSET }, &Show_btree_build_stats,
		false, NULL, NULL
	},
#endif

	{
		{ "explain_pretty_print", PGC_USERSET }, &Explain_pretty_print,
		true, NULL, NULL
	},

	{
		{ "stats_start_collector", PGC_POSTMASTER }, &pgstat_collect_startcollector,
		true, NULL, NULL
	},
	{
		{ "stats_reset_on_server_start", PGC_POSTMASTER }, &pgstat_collect_resetonpmstart,
		true, NULL, NULL
	},
	{
		{ "stats_command_string", PGC_SUSET }, &pgstat_collect_querystring,
		false, NULL, NULL
	},
	{
		{ "stats_row_level", PGC_SUSET }, &pgstat_collect_tuplelevel,
		false, NULL, NULL
	},
	{
		{ "stats_block_level", PGC_SUSET }, &pgstat_collect_blocklevel,
		false, NULL, NULL
	},

	{
		{ "trace_notify", PGC_USERSET }, &Trace_notify,
		false, NULL, NULL
	},

#ifdef LOCK_DEBUG
	{
		{ "trace_locks", PGC_SUSET }, &Trace_locks,
		false, NULL, NULL
	},
	{
		{ "trace_userlocks", PGC_SUSET }, &Trace_userlocks,
		false, NULL, NULL
	},
	{
		{ "trace_lwlocks", PGC_SUSET }, &Trace_lwlocks,
		false, NULL, NULL
	},
	{
		{ "debug_deadlocks", PGC_SUSET }, &Debug_deadlocks,
		false, NULL, NULL
	},
#endif

	{
		{ "hostname_lookup", PGC_SIGHUP }, &HostnameLookup,
		false, NULL, NULL
	},
	{
		{ "show_source_port", PGC_SIGHUP }, &ShowPortNumber,
		false, NULL, NULL
	},

	{
		{ "sql_inheritance", PGC_USERSET }, &SQL_inheritance,
		true, NULL, NULL
	},
	{
		{ "australian_timezones", PGC_USERSET }, &Australian_timezones,
		false, ClearDateCache, NULL
	},
	{
		{ "fixbtree", PGC_POSTMASTER }, &FixBTree,
		true, NULL, NULL
	},
	{
		{ "password_encryption", PGC_USERSET }, &Password_encryption,
		false, NULL, NULL
	},
	{
		{ "transform_null_equals", PGC_USERSET }, &Transform_null_equals,
		false, NULL, NULL
	},

	{
		{ NULL, 0 }, NULL, false, NULL, NULL
	}
};


static struct config_int
			ConfigureNamesInt[] =
{
	{
		{ "geqo_threshold", PGC_USERSET }, &geqo_rels,
		DEFAULT_GEQO_RELS, 2, INT_MAX, NULL, NULL
	},
	{
		{ "geqo_pool_size", PGC_USERSET }, &Geqo_pool_size,
		DEFAULT_GEQO_POOL_SIZE, 0, MAX_GEQO_POOL_SIZE, NULL, NULL
	},
	{
		{ "geqo_effort", PGC_USERSET }, &Geqo_effort,
		1, 1, INT_MAX, NULL, NULL
	},
	{
		{ "geqo_generations", PGC_USERSET }, &Geqo_generations,
		0, 0, INT_MAX, NULL, NULL
	},
	{
		{ "geqo_random_seed", PGC_USERSET }, &Geqo_random_seed,
		-1, INT_MIN, INT_MAX, NULL, NULL
	},

	{
		{ "deadlock_timeout", PGC_POSTMASTER }, &DeadlockTimeout,
		1000, 0, INT_MAX, NULL, NULL
	},

#ifdef HAVE_SYSLOG
	{
		{ "syslog", PGC_SIGHUP }, &Use_syslog,
		0, 0, 2, NULL, NULL
	},
#endif

	/*
	 * Note: There is some postprocessing done in PostmasterMain() to make
	 * sure the buffers are at least twice the number of backends, so the
	 * constraints here are partially unused.
	 */
	{
		{ "max_connections", PGC_POSTMASTER }, &MaxBackends,
		DEF_MAXBACKENDS, 1, INT_MAX, NULL, NULL
	},

	{
		{ "shared_buffers", PGC_POSTMASTER }, &NBuffers,
		DEF_NBUFFERS, 16, INT_MAX, NULL, NULL
	},

	{
		{ "port", PGC_POSTMASTER }, &PostPortNumber,
		DEF_PGPORT, 1, 65535, NULL, NULL
	},

	{
		{ "unix_socket_permissions", PGC_POSTMASTER }, &Unix_socket_permissions,
		0777, 0000, 0777, NULL, NULL
	},

	{
		{ "sort_mem", PGC_USERSET }, &SortMem,
		512, 4 * BLCKSZ / 1024, INT_MAX, NULL, NULL
	},

	{
		{ "vacuum_mem", PGC_USERSET }, &VacuumMem,
		8192, 1024, INT_MAX, NULL, NULL
	},

	{
		{ "max_files_per_process", PGC_BACKEND }, &max_files_per_process,
		1000, 25, INT_MAX, NULL, NULL
	},

#ifdef LOCK_DEBUG
	{
		{ "trace_lock_oidmin", PGC_SUSET }, &Trace_lock_oidmin,
		BootstrapObjectIdData, 1, INT_MAX, NULL, NULL
	},
	{
		{ "trace_lock_table", PGC_SUSET }, &Trace_lock_table,
		0, 0, INT_MAX, NULL, NULL
	},
#endif
	{
		{ "max_expr_depth", PGC_USERSET }, &max_expr_depth,
		DEFAULT_MAX_EXPR_DEPTH, 10, INT_MAX, NULL, NULL
	},

	{
		{ "max_fsm_relations", PGC_POSTMASTER }, &MaxFSMRelations,
		100, 10, INT_MAX, NULL, NULL
	},
	{
		{ "max_fsm_pages", PGC_POSTMASTER }, &MaxFSMPages,
		10000, 1000, INT_MAX, NULL, NULL
	},

	{
		{ "max_locks_per_transaction", PGC_POSTMASTER }, &max_locks_per_xact,
		64, 10, INT_MAX, NULL, NULL
	},

	{
		{ "authentication_timeout", PGC_SIGHUP }, &AuthenticationTimeout,
		60, 1, 600, NULL, NULL
	},

	{
		{ "pre_auth_delay", PGC_SIGHUP }, &PreAuthDelay,
		0, 0, 60, NULL, NULL
	},

	{
		{ "checkpoint_segments", PGC_SIGHUP }, &CheckPointSegments,
		3, 1, INT_MAX, NULL, NULL
	},

	{
		{ "checkpoint_timeout", PGC_SIGHUP }, &CheckPointTimeout,
		300, 30, 3600, NULL, NULL
	},

	{
		{ "wal_buffers", PGC_POSTMASTER }, &XLOGbuffers,
		8, 4, INT_MAX, NULL, NULL
	},

	{
		{ "wal_files", PGC_SIGHUP }, &XLOGfiles,
		0, 0, 64, NULL, NULL
	},

	{
		{ "wal_debug", PGC_SUSET }, &XLOG_DEBUG,
		0, 0, 16, NULL, NULL
	},

	{
		{ "commit_delay", PGC_USERSET }, &CommitDelay,
		0, 0, 100000, NULL, NULL
	},

	{
		{ "commit_siblings", PGC_USERSET }, &CommitSiblings,
		5, 1, 1000, NULL, NULL
	},

	{
		{ NULL, 0 }, NULL, 0, 0, 0, NULL, NULL
	}
};


static struct config_real
			ConfigureNamesReal[] =
{
	{
		{ "effective_cache_size", PGC_USERSET }, &effective_cache_size,
		DEFAULT_EFFECTIVE_CACHE_SIZE, 0, DBL_MAX, NULL, NULL
	},
	{
		{ "random_page_cost", PGC_USERSET }, &random_page_cost,
		DEFAULT_RANDOM_PAGE_COST, 0, DBL_MAX, NULL, NULL
	},
	{
		{ "cpu_tuple_cost", PGC_USERSET }, &cpu_tuple_cost,
		DEFAULT_CPU_TUPLE_COST, 0, DBL_MAX, NULL, NULL
	},
	{
		{ "cpu_index_tuple_cost", PGC_USERSET }, &cpu_index_tuple_cost,
		DEFAULT_CPU_INDEX_TUPLE_COST, 0, DBL_MAX, NULL, NULL
	},
	{
		{ "cpu_operator_cost", PGC_USERSET }, &cpu_operator_cost,
		DEFAULT_CPU_OPERATOR_COST, 0, DBL_MAX, NULL, NULL
	},

	{
		{ "geqo_selection_bias", PGC_USERSET }, &Geqo_selection_bias,
		DEFAULT_GEQO_SELECTION_BIAS, MIN_GEQO_SELECTION_BIAS,
		MAX_GEQO_SELECTION_BIAS, NULL, NULL
	},

	{
		{ "seed", PGC_USERSET, GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL },
		&phony_random_seed,
		0.5, 0.0, 1.0, assign_random_seed, show_random_seed
	},

	{
		{ NULL, 0 }, NULL, 0.0, 0.0, 0.0, NULL, NULL
	}
};


static struct config_string
			ConfigureNamesString[] =
{
	{
		{ "client_encoding", PGC_USERSET }, &client_encoding_string,
		"SQL_ASCII", assign_client_encoding, NULL
	},

	{
		{ "client_min_messages", PGC_USERSET }, &client_min_messages_str,
		client_min_messages_str_default, assign_client_min_messages, NULL
	},

	{
		{ "DateStyle", PGC_USERSET, GUC_LIST_INPUT }, &datestyle_string,
		"ISO, US", assign_datestyle, show_datestyle
	},

	{
		{ "default_transaction_isolation", PGC_USERSET }, &default_iso_level_string,
		"read committed", assign_defaultxactisolevel, NULL
	},

	{
		{ "dynamic_library_path", PGC_SUSET }, &Dynamic_library_path,
		"$libdir", NULL, NULL
	},

	{
		{ "krb_server_keyfile", PGC_POSTMASTER }, &pg_krb_server_keyfile,
		PG_KRB_SRVTAB, NULL, NULL
	},

	{
		{ "lc_messages", PGC_SUSET }, &locale_messages,
		"", locale_messages_assign, NULL
	},

	{
		{ "lc_monetary", PGC_USERSET }, &locale_monetary,
		"", locale_monetary_assign, NULL
	},

	{
		{ "lc_numeric", PGC_USERSET }, &locale_numeric,
		"", locale_numeric_assign, NULL
	},

	{
		{ "lc_time", PGC_USERSET }, &locale_time,
		"", locale_time_assign, NULL
	},

	{
		{ "search_path", PGC_USERSET, GUC_LIST_INPUT | GUC_LIST_QUOTE },
		&namespace_search_path,
		"$user,public", assign_search_path, NULL
	},

	{
		{ "server_encoding", PGC_USERSET }, &server_encoding_string,
		"SQL_ASCII", assign_server_encoding, show_server_encoding
	},

	{
		{ "server_min_messages", PGC_USERSET }, &server_min_messages_str,
		server_min_messages_str_default, assign_server_min_messages, NULL
	},

	{
		{ "session_authorization", PGC_USERSET, GUC_NO_SHOW_ALL | GUC_NO_RESET_ALL },
		&session_authorization_string,
		NULL, assign_session_authorization, show_session_authorization
	},

#ifdef HAVE_SYSLOG
	{
		{ "syslog_facility", PGC_POSTMASTER }, &Syslog_facility,
		"LOCAL0", assign_facility, NULL
	},
	{
		{ "syslog_ident", PGC_POSTMASTER }, &Syslog_ident,
		"postgres", NULL, NULL
	},
#endif

	{
		{ "TimeZone", PGC_USERSET }, &timezone_string,
		"UNKNOWN", assign_timezone, show_timezone
	},

	{
		{ "TRANSACTION ISOLATION LEVEL", PGC_USERSET, GUC_NO_RESET_ALL },
		&XactIsoLevel_string,
		NULL, assign_XactIsoLevel, show_XactIsoLevel
	},

	{
		{ "unix_socket_group", PGC_POSTMASTER }, &Unix_socket_group,
		"", NULL, NULL
	},

	{
		{ "unix_socket_directory", PGC_POSTMASTER }, &UnixSocketDir,
		"", NULL, NULL
	},

	{
		{ "virtual_host", PGC_POSTMASTER }, &VirtualHost,
		"", NULL, NULL
	},

	{
		{ "wal_sync_method", PGC_SIGHUP }, &XLOG_sync_method,
		XLOG_sync_method_default, assign_xlog_sync_method, NULL
	},

	{
		{ NULL, 0 }, NULL, NULL, NULL, NULL
	}
};

/******** end of options list ********/


/*
 * Actual lookup of variables is done through this single, sorted array.
 */
static struct config_generic **guc_variables;
static int num_guc_variables;

static bool guc_dirty;			/* TRUE if need to do commit/abort work */

static char *guc_string_workspace; /* for avoiding memory leaks */


static int guc_var_compare(const void *a, const void *b);
static void _ShowOption(struct config_generic *record);


/*
 * Build the sorted array.  This is split out so that it could be
 * re-executed after startup (eg, we could allow loadable modules to
 * add vars, and then we'd need to re-sort).
 */
static void
build_guc_variables(void)
{
	int			num_vars = 0;
	struct config_generic **guc_vars;
	int			i;

	for (i = 0; ConfigureNamesBool[i].gen.name; i++)
	{
		struct config_bool *conf = &ConfigureNamesBool[i];

		/* Rather than requiring vartype to be filled in by hand, do this: */
		conf->gen.vartype = PGC_BOOL;
		num_vars++;
	}

	for (i = 0; ConfigureNamesInt[i].gen.name; i++)
	{
		struct config_int *conf = &ConfigureNamesInt[i];

		conf->gen.vartype = PGC_INT;
		num_vars++;
	}

	for (i = 0; ConfigureNamesReal[i].gen.name; i++)
	{
		struct config_real *conf = &ConfigureNamesReal[i];

		conf->gen.vartype = PGC_REAL;
		num_vars++;
	}

	for (i = 0; ConfigureNamesString[i].gen.name; i++)
	{
		struct config_string *conf = &ConfigureNamesString[i];

		conf->gen.vartype = PGC_STRING;
		num_vars++;
	}

	guc_vars = (struct config_generic **)
		malloc(num_vars * sizeof(struct config_generic *));
	if (!guc_vars)
		elog(PANIC, "out of memory");

	num_vars = 0;

	for (i = 0; ConfigureNamesBool[i].gen.name; i++)
		guc_vars[num_vars++] = & ConfigureNamesBool[i].gen;

	for (i = 0; ConfigureNamesInt[i].gen.name; i++)
		guc_vars[num_vars++] = & ConfigureNamesInt[i].gen;

	for (i = 0; ConfigureNamesReal[i].gen.name; i++)
		guc_vars[num_vars++] = & ConfigureNamesReal[i].gen;

	for (i = 0; ConfigureNamesString[i].gen.name; i++)
		guc_vars[num_vars++] = & ConfigureNamesString[i].gen;

	qsort((void *) guc_vars, num_vars, sizeof(struct config_generic *),
		  guc_var_compare);

	if (guc_variables)
		free(guc_variables);
	guc_variables = guc_vars;
	num_guc_variables = num_vars;
}


/*
 * Look up option NAME. If it exists, return a pointer to its record,
 * else return NULL.
 */
static struct config_generic *
find_option(const char *name)
{
	const char **key = &name;
	struct config_generic **res;

	Assert(name);

	/*
	 * by equating const char ** with struct config_generic *, we are
	 * assuming the name field is first in config_generic.
	 */
	res = (struct config_generic**) bsearch((void *) &key,
											(void *) guc_variables,
											num_guc_variables,
											sizeof(struct config_generic *),
											guc_var_compare);
	if (res)
		return *res;
	return NULL;
}


/*
 * comparator for qsorting and bsearching guc_variables array
 */
static int
guc_var_compare(const void *a, const void *b)
{
	struct config_generic *confa = *(struct config_generic **) a;
	struct config_generic *confb = *(struct config_generic **) b;
	const char *namea;
	const char *nameb;

	/*
	 * The temptation to use strcasecmp() here must be resisted, because
	 * the array ordering has to remain stable across setlocale() calls.
	 * So, build our own with a simple ASCII-only downcasing.
	 */
	namea = confa->name;
	nameb = confb->name;
	while (*namea && *nameb)
	{
		char		cha = *namea++;
		char		chb = *nameb++;

		if (cha >= 'A' && cha <= 'Z')
			cha += 'a' - 'A';
		if (chb >= 'A' && chb <= 'Z')
			chb += 'a' - 'A';
		if (cha != chb)
			return cha - chb;
	}
	if (*namea)
		return 1;				/* a is longer */
	if (*nameb)
		return -1;				/* b is longer */
	return 0;
}


/*
 * Initialize GUC options during program startup.
 */
void
InitializeGUCOptions(void)
{
	int			i;
	char	   *env;

	/*
	 * Build sorted array of all GUC variables.
	 */
	build_guc_variables();

	/*
	 * Load all variables with their compiled-in defaults, and initialize
	 * status fields as needed.
	 *
	 * Note: any errors here are reported with plain ol' printf, since we
	 * shouldn't assume that elog will work before we've initialized its
	 * config variables.  An error here would be unexpected anyway...
	 */
	for (i = 0; i < num_guc_variables; i++)
	{
		struct config_generic *gconf = guc_variables[i];

		gconf->status = 0;
		gconf->reset_source = PGC_S_DEFAULT;
		gconf->session_source = PGC_S_DEFAULT;
		gconf->tentative_source = PGC_S_DEFAULT;
		gconf->source = PGC_S_DEFAULT;

		switch (gconf->vartype)
		{
			case PGC_BOOL:
			{
				struct config_bool *conf = (struct config_bool *) gconf;

				if (conf->assign_hook)
					if (!(*conf->assign_hook) (conf->reset_val, true, false))
						fprintf(stderr, "Failed to initialize %s",
								conf->gen.name);
				*conf->variable = conf->reset_val;
				conf->session_val = 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, false))
						fprintf(stderr, "Failed to initialize %s",
								conf->gen.name);
				*conf->variable = conf->reset_val;
				conf->session_val = 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, false))
						fprintf(stderr, "Failed to initialize %s",
								conf->gen.name);
				*conf->variable = conf->reset_val;
				conf->session_val = conf->reset_val;
				break;
			}
			case PGC_STRING:
			{
				struct config_string *conf = (struct config_string *) gconf;
				char	   *str;

				*conf->variable = NULL;
				conf->reset_val = NULL;
				conf->session_val = NULL;
				conf->tentative_val = NULL;

				if (conf->boot_val == NULL)
				{
					/* Cannot set value yet */
					break;
				}

				str = strdup(conf->boot_val);
				if (str == NULL)
					elog(PANIC, "out of memory");
				conf->reset_val = str;

				if (conf->assign_hook)
				{
					const char   *newstr;

					newstr = (*conf->assign_hook) (str, true, false);
					if (newstr == NULL)
					{
						fprintf(stderr, "Failed to initialize %s",
								conf->gen.name);
					}
					else if (newstr != str)
					{
						free(str);
						/* See notes in set_config_option about casting */
						str = (char *) newstr;
						conf->reset_val = str;
					}
				}
				*conf->variable = str;
				conf->session_val = str;
				break;
			}
		}
	}

	guc_dirty = false;

	guc_string_workspace = NULL;

	/*
	 * Prevent any attempt to override TRANSACTION ISOLATION LEVEL from
	 * non-interactive sources.
	 */
	SetConfigOption("TRANSACTION ISOLATION LEVEL", "default",
					PGC_POSTMASTER, PGC_S_OVERRIDE);

	/*
	 * For historical reasons, some GUC parameters can receive defaults
	 * from environment variables.  Process those settings.
	 */

	env = getenv("PGPORT");
	if (env != NULL)
		SetConfigOption("port", env, PGC_POSTMASTER, PGC_S_ENV_VAR);

	env = getenv("PGDATESTYLE");
	if (env != NULL)
		SetConfigOption("datestyle", env, PGC_POSTMASTER, PGC_S_ENV_VAR);

	env = getenv("TZ");
	if (env != NULL)
		SetConfigOption("timezone", env, PGC_POSTMASTER, PGC_S_ENV_VAR);

#ifdef MULTIBYTE
	env = getenv("PGCLIENTENCODING");
	if (env != NULL)
		SetConfigOption("client_encoding", env, PGC_POSTMASTER, PGC_S_ENV_VAR);
#endif
}


/*
 * Reset all options to their saved default values (implements RESET ALL)
 */
void
ResetAllOptions(void)
{
	int			i;

	for (i = 0; i < num_guc_variables; i++)
	{
		struct config_generic *gconf = guc_variables[i];

		/* Don't reset non-SET-able values */
		if (gconf->context != PGC_SUSET && gconf->context != PGC_USERSET)
			continue;
		/* Don't reset if special exclusion from RESET ALL */
		if (gconf->flags & GUC_NO_RESET_ALL)
			continue;
		/* No need to reset if wasn't SET */
		if (gconf->source <= PGC_S_OVERRIDE)
			continue;

		switch (gconf->vartype)
		{
			case PGC_BOOL:
			{
				struct config_bool *conf = (struct config_bool *) gconf;

				if (conf->assign_hook)
					if (!(*conf->assign_hook) (conf->reset_val, true, true))
						elog(ERROR, "Failed to reset %s", conf->gen.name);
				*conf->variable = conf->reset_val;
				conf->tentative_val = conf->reset_val;
				conf->gen.source = conf->gen.reset_source;
				conf->gen.tentative_source = conf->gen.reset_source;
				conf->gen.status |= GUC_HAVE_TENTATIVE;
				guc_dirty = true;
				break;
			}
			case PGC_INT:
			{
				struct config_int *conf = (struct config_int *) gconf;

				if (conf->assign_hook)
					if (!(*conf->assign_hook) (conf->reset_val, true, true))
						elog(ERROR, "Failed to reset %s", conf->gen.name);
				*conf->variable = conf->reset_val;
				conf->tentative_val = conf->reset_val;
				conf->gen.source = conf->gen.reset_source;
				conf->gen.tentative_source = conf->gen.reset_source;
				conf->gen.status |= GUC_HAVE_TENTATIVE;
				guc_dirty = true;
				break;
			}
			case PGC_REAL:
			{
				struct config_real *conf = (struct config_real *) gconf;

				if (conf->assign_hook)
					if (!(*conf->assign_hook) (conf->reset_val, true, true))
						elog(ERROR, "Failed to reset %s", conf->gen.name);
				*conf->variable = conf->reset_val;
				conf->tentative_val = conf->reset_val;
				conf->gen.source = conf->gen.reset_source;
				conf->gen.tentative_source = conf->gen.reset_source;
				conf->gen.status |= GUC_HAVE_TENTATIVE;
				guc_dirty = true;
				break;
			}
			case PGC_STRING:
			{
				struct config_string *conf = (struct config_string *) gconf;
				char	   *str;

				if (conf->reset_val == NULL)
				{
					/* Nothing to reset to, as yet; so do nothing */
					break;
				}

				/* We need not strdup here */
				str = conf->reset_val;

				if (conf->assign_hook)
				{
					const char   *newstr;

					newstr = (*conf->assign_hook) (str, true, true);
					if (newstr == NULL)
						elog(ERROR, "Failed to reset %s", conf->gen.name);
					else if (newstr != str)
					{
						/* See notes in set_config_option about casting */
						str = (char *) newstr;
					}
				}

				SET_STRING_VARIABLE(conf, str);
				SET_STRING_TENTATIVE_VAL(conf, str);
				conf->gen.source = conf->gen.reset_source;
				conf->gen.tentative_source = conf->gen.reset_source;
				conf->gen.status |= GUC_HAVE_TENTATIVE;
				guc_dirty = true;
				break;
			}
		}
	}
}


/*
 * Do GUC processing at transaction commit or abort.
 */
void
AtEOXact_GUC(bool isCommit)
{
	int			i;

	/* Quick exit if nothing's changed in this transaction */
	if (!guc_dirty)
		return;

	/* Prevent memory leak if elog during an assign_hook */
	if (guc_string_workspace)
	{
		free(guc_string_workspace);
		guc_string_workspace = NULL;
	}

	for (i = 0; i < num_guc_variables; i++)
	{
		struct config_generic *gconf = guc_variables[i];

		/* Skip if nothing's happened to this var in this transaction */
		if (gconf->status == 0)
			continue;

		switch (gconf->vartype)
		{
			case PGC_BOOL:
			{
				struct config_bool *conf = (struct config_bool *) gconf;

				if (isCommit && (conf->gen.status & GUC_HAVE_TENTATIVE))
				{
					conf->session_val = conf->tentative_val;
					conf->gen.session_source = conf->gen.tentative_source;
				}

				if (*conf->variable != conf->session_val)
				{
					if (conf->assign_hook)
						if (!(*conf->assign_hook) (conf->session_val,
												   true, false))
							elog(LOG, "Failed to commit %s", conf->gen.name);
					*conf->variable = conf->session_val;
				}
				conf->gen.source = conf->gen.session_source;
				conf->gen.status = 0;
				break;
			}
			case PGC_INT:
			{
				struct config_int *conf = (struct config_int *) gconf;

				if (isCommit && (conf->gen.status & GUC_HAVE_TENTATIVE))
				{
					conf->session_val = conf->tentative_val;
					conf->gen.session_source = conf->gen.tentative_source;
				}

				if (*conf->variable != conf->session_val)
				{
					if (conf->assign_hook)
						if (!(*conf->assign_hook) (conf->session_val,
												   true, false))
							elog(LOG, "Failed to commit %s", conf->gen.name);
					*conf->variable = conf->session_val;
				}
				conf->gen.source = conf->gen.session_source;
				conf->gen.status = 0;
				break;
			}
			case PGC_REAL:
			{
				struct config_real *conf = (struct config_real *) gconf;

				if (isCommit && (conf->gen.status & GUC_HAVE_TENTATIVE))
				{
					conf->session_val = conf->tentative_val;
					conf->gen.session_source = conf->gen.tentative_source;
				}

				if (*conf->variable != conf->session_val)
				{
					if (conf->assign_hook)
						if (!(*conf->assign_hook) (conf->session_val,
												   true, false))
							elog(LOG, "Failed to commit %s", conf->gen.name);
					*conf->variable = conf->session_val;
				}
				conf->gen.source = conf->gen.session_source;
				conf->gen.status = 0;
				break;
			}
			case PGC_STRING:
			{
				struct config_string *conf = (struct config_string *) gconf;

				if (isCommit && (conf->gen.status & GUC_HAVE_TENTATIVE))
				{
					SET_STRING_SESSION_VAL(conf, conf->tentative_val);
					conf->gen.session_source = conf->gen.tentative_source;
					conf->tentative_val = NULL;	/* transfer ownership */
				}
				else
				{
					SET_STRING_TENTATIVE_VAL(conf, NULL);
				}

				if (*conf->variable != conf->session_val)
				{
					char	   *str = conf->session_val;

					if (conf->assign_hook)
					{
						const char   *newstr;

						newstr = (*conf->assign_hook) (str, true, false);
						if (newstr == NULL)
							elog(LOG, "Failed to commit %s", conf->gen.name);
						else if (newstr != str)
						{
							/* See notes in set_config_option about casting */
							str = (char *) newstr;
							SET_STRING_SESSION_VAL(conf, str);
						}
					}

					SET_STRING_VARIABLE(conf, str);
				}
				conf->gen.source = conf->gen.session_source;
				conf->gen.status = 0;
				break;
			}
		}
	}

	guc_dirty = false;
}


/*
 * Try to interpret value as boolean value.  Valid values are: true,
 * false, yes, no, on, off, 1, 0.  If the string parses okay, return
 * true, else false.  If result is not NULL, return the parsing result
 * there.
 */
static bool
parse_bool(const char *value, bool *result)
{
	size_t		len = strlen(value);

	if (strncasecmp(value, "true", len) == 0)
	{
		if (result)
			*result = true;
	}
	else if (strncasecmp(value, "false", len) == 0)
	{
		if (result)
			*result = false;
	}

	else if (strncasecmp(value, "yes", len) == 0)
	{
		if (result)
			*result = true;
	}
	else if (strncasecmp(value, "no", len) == 0)
	{
		if (result)
			*result = false;
	}

	else if (strcasecmp(value, "on") == 0)
	{
		if (result)
			*result = true;
	}
	else if (strcasecmp(value, "off") == 0)
	{
		if (result)
			*result = false;
	}

	else if (strcasecmp(value, "1") == 0)
	{
		if (result)
			*result = true;
	}
	else if (strcasecmp(value, "0") == 0)
	{
		if (result)
			*result = false;
	}

	else
		return false;
	return true;
}



/*
 * Try to parse value as an integer.  The accepted formats are the
 * usual decimal, octal, or hexadecimal formats.  If the string parses
 * okay, return true, else false.  If result is not NULL, return the
 * value there.
 */
static bool
parse_int(const char *value, int *result)
{
	long		val;
	char	   *endptr;

	errno = 0;
	val = strtol(value, &endptr, 0);
	if (endptr == value || *endptr != '\0' || errno == ERANGE
#ifdef HAVE_LONG_INT_64
	/* if long > 32 bits, check for overflow of int4 */
		|| val != (long) ((int32) val)
#endif
		)
		return false;
	if (result)
		*result = (int) val;
	return true;
}



/*
 * Try to parse value as a floating point constant in the usual
 * format.	If the value parsed okay return true, else false.  If
 * result is not NULL, return the semantic value there.
 */
static bool
parse_real(const char *value, double *result)
{
	double		val;
	char	   *endptr;

	errno = 0;
	val = strtod(value, &endptr);
	if (endptr == value || *endptr != '\0' || errno == ERANGE)
		return false;
	if (result)
		*result = val;
	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 DoIt 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
 * elog(ERROR) is thrown *unless* this is called in a context where we
 * don't want to elog (currently, startup or SIGHUP config file reread).
 * In that case we write a suitable error message via elog(DEBUG) and
 * return false. This is working around the deficiencies in the elog
 * 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 DoIt)
{
	struct config_generic *record;
	int			elevel;
	bool		interactive;
	bool		makeDefault;

	if (context == PGC_SIGHUP || source == PGC_S_DEFAULT)
		elevel = DEBUG1;
	else if (source == PGC_S_DATABASE || source == PGC_S_USER)
		elevel = INFO;
	else
		elevel = ERROR;

	record = find_option(name);
	if (record == NULL)
	{
		elog(elevel, "'%s' is not a valid option name", 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 context. In that case we just ignore the attempt and
	 * return true.
	 */
	switch (record->context)
	{
		case PGC_POSTMASTER:
			if (context == PGC_SIGHUP)
				return true;
			if (context != PGC_POSTMASTER)
			{
				elog(elevel, "'%s' cannot be changed after server start",
					 name);
				return false;
			}
			break;
		case PGC_SIGHUP:
			if (context != PGC_SIGHUP && context != PGC_POSTMASTER)
			{
				elog(elevel, "'%s' cannot be changed now", name);
				return false;
			}

			/*
			 * Hmm, the idea of the SIGHUP context is "ought to be global,
			 * but can be changed after postmaster start". But there's
			 * nothing that prevents a crafty administrator from sending
			 * SIGHUP signals to individual backends only.
			 */
			break;
		case PGC_BACKEND:
			if (context == PGC_SIGHUP)
			{
				/*
				 * If a PGC_BACKEND parameter is changed in the config
				 * file, we want to accept the new value in the postmaster
				 * (whence it will propagate to subsequently-started
				 * backends), but ignore it in existing backends.  This is
				 * a tad klugy, but necessary because we don't re-read the
				 * config file during backend start.
				 */
				if (IsUnderPostmaster)
					return true;
			}
			else if (context != PGC_BACKEND && context != PGC_POSTMASTER)
			{
				elog(elevel, "'%s' cannot be set after connection start",
					 name);
				return false;
			}
			break;
		case PGC_SUSET:
			if (context == PGC_USERSET || context == PGC_BACKEND)
			{
				elog(elevel, "'%s': permission denied", name);
				return false;
			}
			break;
		case PGC_USERSET:
			/* always okay */
			break;
	}

	/* Should we report errors interactively? */
	interactive = (source >= PGC_S_SESSION);
	/*
	 * Should we set reset/session values?  (If so, the behavior is not
	 * transactional.)
	 */
	makeDefault = DoIt && (source <= PGC_S_OVERRIDE) && (value != NULL);

	/*
	 * Ignore attempted set if overridden by previously processed setting.
	 * However, if DoIt is false then plow ahead anyway since we are trying
	 * to find out if the value is potentially good, not actually use it.
	 * Also keep going if makeDefault is true, since we may want to set
	 * the reset/session values even if we can't set the variable itself.
	 */
	if (record->source > source)
	{
		if (DoIt && !makeDefault)
		{
			elog(DEBUG2, "%s: setting ignored because previous source is higher priority",
				 name);
			return true;
		}
		DoIt = false;			/* we won't change the variable itself */
	}

	/*
	 * 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))
					{
						elog(elevel, "option '%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, DoIt, interactive))
					{
						elog(elevel, "invalid value for option '%s': %d",
							 name, (int) newval);
						return false;
					}

				if (DoIt || makeDefault)
				{
					if (DoIt)
					{
						*conf->variable = newval;
						conf->gen.source = source;
					}
					if (makeDefault)
					{
						if (conf->gen.reset_source <= source)
						{
							conf->reset_val = newval;
							conf->gen.reset_source = source;
						}
						if (conf->gen.session_source <= source)
						{
							conf->session_val = newval;
							conf->gen.session_source = source;
						}
					}
					else if (isLocal)
					{
						conf->gen.status |= GUC_HAVE_LOCAL;
						guc_dirty = true;
					}
					else
					{
						conf->tentative_val = newval;
						conf->gen.tentative_source = source;
						conf->gen.status |= GUC_HAVE_TENTATIVE;
						guc_dirty = true;
					}
				}
				break;
			}

		case PGC_INT:
			{
				struct config_int *conf = (struct config_int *) record;
				int			newval;

				if (value)
				{
					if (!parse_int(value, &newval))
					{
						elog(elevel, "option '%s' expects an integer value",
							 name);
						return false;
					}
					if (newval < conf->min || newval > conf->max)
					{
						elog(elevel, "option '%s' value %d is outside"
							 " of permissible range [%d .. %d]",
							 name, newval, 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, DoIt, interactive))
					{
						elog(elevel, "invalid value for option '%s': %d",
							 name, newval);
						return false;
					}

				if (DoIt || makeDefault)
				{
					if (DoIt)
					{
						*conf->variable = newval;
						conf->gen.source = source;
					}
					if (makeDefault)
					{
						if (conf->gen.reset_source <= source)
						{
							conf->reset_val = newval;
							conf->gen.reset_source = source;
						}
						if (conf->gen.session_source <= source)
						{
							conf->session_val = newval;
							conf->gen.session_source = source;
						}
					}
					else if (isLocal)
					{
						conf->gen.status |= GUC_HAVE_LOCAL;
						guc_dirty = true;
					}
					else
					{
						conf->tentative_val = newval;
						conf->gen.tentative_source = source;
						conf->gen.status |= GUC_HAVE_TENTATIVE;
						guc_dirty = true;
					}
				}
				break;
			}

		case PGC_REAL:
			{
				struct config_real *conf = (struct config_real *) record;
				double		newval;

				if (value)
				{
					if (!parse_real(value, &newval))
					{
						elog(elevel, "option '%s' expects a real number",
							 name);
						return false;
					}
					if (newval < conf->min || newval > conf->max)
					{
						elog(elevel, "option '%s' value %g is outside"
							 " of permissible range [%g .. %g]",
							 name, newval, 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, DoIt, interactive))
					{
						elog(elevel, "invalid value for option '%s': %g",
							 name, newval);
						return false;
					}

				if (DoIt || makeDefault)
				{
					if (DoIt)
					{
						*conf->variable = newval;
						conf->gen.source = source;
					}
					if (makeDefault)
					{
						if (conf->gen.reset_source <= source)
						{
							conf->reset_val = newval;
							conf->gen.reset_source = source;
						}
						if (conf->gen.session_source <= source)
						{
							conf->session_val = newval;
							conf->gen.session_source = source;
						}
					}
					else if (isLocal)
					{
						conf->gen.status |= GUC_HAVE_LOCAL;
						guc_dirty = true;
					}
					else
					{
						conf->tentative_val = newval;
						conf->gen.tentative_source = source;
						conf->gen.status |= GUC_HAVE_TENTATIVE;
						guc_dirty = true;
					}
				}
				break;
			}

		case PGC_STRING:
			{
				struct config_string *conf = (struct config_string *) record;
				char	   *newval;

				if (value)
				{
					newval = strdup(value);
					if (newval == NULL)
					{
						elog(elevel, "out of memory");
						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 = strdup(conf->reset_val);
					if (newval == NULL)
					{
						elog(elevel, "out of memory");
						return false;
					}
					source = conf->gen.reset_source;
				}
				else
				{
					/* Nothing to reset to, as yet; so do nothing */
					break;
				}

				/*
				 * Remember string in workspace, so that we can free it
				 * and avoid a permanent memory leak if hook elogs.
				 */
				if (guc_string_workspace)
					free(guc_string_workspace);
				guc_string_workspace = newval;

				if (conf->assign_hook)
				{
					const char   *hookresult;

					hookresult = (*conf->assign_hook) (newval,
													   DoIt, interactive);
					guc_string_workspace = NULL;
					if (hookresult == NULL)
					{
						free(newval);
						elog(elevel, "invalid value for option '%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;
					}
				}

				guc_string_workspace = NULL;

				if (DoIt || makeDefault)
				{
					if (DoIt)
					{
						SET_STRING_VARIABLE(conf, newval);
						conf->gen.source = source;
					}
					if (makeDefault)
					{
						if (conf->gen.reset_source <= source)
						{
							SET_STRING_RESET_VAL(conf, newval);
							conf->gen.reset_source = source;
						}
						if (conf->gen.session_source <= source)
						{
							SET_STRING_SESSION_VAL(conf, newval);
							conf->gen.session_source = source;
						}
						/* Perhaps we didn't install newval anywhere */
						if (newval != *conf->variable &&
							newval != conf->session_val &&
							newval != conf->reset_val)
							free(newval);
					}
					else if (isLocal)
					{
						conf->gen.status |= GUC_HAVE_LOCAL;
						guc_dirty = true;
					}
					else
					{
						SET_STRING_TENTATIVE_VAL(conf, newval);
						conf->gen.tentative_source = source;
						conf->gen.status |= GUC_HAVE_TENTATIVE;
						guc_dirty = true;
					}
				}
				else
				{
					free(newval);
				}
				break;
			}
	}

	return true;
}



/*
 * Set a config option to the given value. See also set_config_option,
 * this is just the wrapper to be called from outside GUC.  NB: this
 * is used only for non-transactional operations.
 */
void
SetConfigOption(const char *name, const char *value,
				GucContext context, GucSource source)
{
	(void) set_config_option(name, value, context, source, false, true);
}



/*
 * Fetch the current value of the option `name'. If the option doesn't exist,
 * throw an elog and don't return.
 *
 * The string is *not* allocated for modification and is really only
 * valid until the next call to configuration related functions.
 */
const char *
GetConfigOption(const char *name)
{
	struct config_generic *record;
	static char buffer[256];

	record = find_option(name);
	if (record == NULL)
		elog(ERROR, "Option '%s' is not recognized", name);

	switch (record->vartype)
	{
		case PGC_BOOL:
			return *((struct config_bool *) record)->variable ? "on" : "off";

		case PGC_INT:
			snprintf(buffer, sizeof(buffer), "%d",
					 *((struct config_int *) record)->variable);
			return buffer;

		case PGC_REAL:
			snprintf(buffer, sizeof(buffer), "%g",
					 *((struct config_real *) record)->variable);
			return buffer;

		case PGC_STRING:
			return *((struct config_string *) record)->variable;
	}
	return NULL;
}

/*
 * Get the RESET value associated with the given option.
 */
const char *
GetConfigOptionResetString(const char *name)
{
	struct config_generic *record;
	static char buffer[256];

	record = find_option(name);
	if (record == NULL)
		elog(ERROR, "Option '%s' is not recognized", name);

	switch (record->vartype)
	{
		case PGC_BOOL:
			return ((struct config_bool *) record)->reset_val ? "on" : "off";

		case PGC_INT:
			snprintf(buffer, sizeof(buffer), "%d",
					 ((struct config_int *) record)->reset_val);
			return buffer;

		case PGC_REAL:
			snprintf(buffer, sizeof(buffer), "%g",
					 ((struct config_real *) record)->reset_val);
			return buffer;

		case PGC_STRING:
			return ((struct config_string *) record)->reset_val;
	}
	return NULL;
}



/*
 * flatten_set_variable_args
 *		Given a parsenode List as emitted by the grammar for SET,
 *		convert to the flat string representation used by GUC.
 *
 * We need to be told the name of the variable the args are for, because
 * the flattening rules vary (ugh).
 *
 * The result is NULL if input is NIL (ie, SET ... TO DEFAULT), otherwise
 * a palloc'd string.
 */
char *
flatten_set_variable_args(const char *name, List *args)
{
	struct config_generic *record;
	int			flags;
	StringInfoData buf;
	List		*l;

	/* Fast path if just DEFAULT */
	if (args == NIL)
		return NULL;

	record = find_option(name);
	if (record == NULL)
		flags = 0;				/* default assumptions */
	else
		flags = record->flags;

	/* Complain if list input and non-list variable */
	if ((flags & GUC_LIST_INPUT) == 0 &&
		lnext(args) != NIL)
		elog(ERROR, "SET %s takes only one argument", name);

	initStringInfo(&buf);

	foreach(l, args)
	{
		A_Const    *arg = (A_Const *) lfirst(l);
		char	   *val;

		if (l != args)
			appendStringInfo(&buf, ", ");

		if (!IsA(arg, A_Const))
			elog(ERROR, "flatten_set_variable_args: unexpected input");

		switch (nodeTag(&arg->val))
		{
			case T_Integer:
				appendStringInfo(&buf, "%ld", intVal(&arg->val));
				break;
			case T_Float:
				/* represented as a string, so just copy it */
				appendStringInfo(&buf, "%s", strVal(&arg->val));
				break;
			case T_String:
				val = strVal(&arg->val);
				if (arg->typename != NULL)
				{
					/*
					 * Must be a ConstInterval argument for TIME ZONE.
					 * Coerce to interval and back to normalize the value
					 * and account for any typmod.
					 */
					Datum	interval;
					char   *intervalout;

					interval =
						DirectFunctionCall3(interval_in,
											CStringGetDatum(val),
											ObjectIdGetDatum(InvalidOid),
											Int32GetDatum(arg->typename->typmod));

					intervalout =
						DatumGetCString(DirectFunctionCall3(interval_out,
															interval,
															ObjectIdGetDatum(InvalidOid),
															Int32GetDatum(-1)));
					appendStringInfo(&buf, "INTERVAL '%s'", intervalout);
				}
				else
				{
					/*
					 * Plain string literal or identifier.  For quote mode,
					 * quote it if it's not a vanilla identifier.
					 */
					if (flags & GUC_LIST_QUOTE)
						appendStringInfo(&buf, "%s", quote_identifier(val));
					else
						appendStringInfo(&buf, "%s", val);
				}
				break;
			default:
				elog(ERROR, "flatten_set_variable_args: unexpected input");
				break;
		}
	}

	return buf.data;
}


/*
 * SET command
 */
void
SetPGVariable(const char *name, List *args, bool is_local)
{
	char	   *argstring = flatten_set_variable_args(name, args);

	/* Note SET DEFAULT (argstring == NULL) is equivalent to RESET */
	set_config_option(name,
					  argstring,
					  (superuser() ? PGC_SUSET : PGC_USERSET),
					  PGC_S_SESSION,
					  is_local,
					  true);
}

/*
 * SHOW command
 */
void
GetPGVariable(const char *name)
{
	if (strcasecmp(name, "all") == 0)
		ShowAllGUCConfig();
	else
		ShowGUCConfigOption(name);
}

/*
 * RESET command
 */
void
ResetPGVariable(const char *name)
{
	if (strcasecmp(name, "all") == 0)
		ResetAllOptions();
	else
		set_config_option(name,
						  NULL,
						  (superuser() ? PGC_SUSET : PGC_USERSET),
						  PGC_S_SESSION,
						  false,
						  true);
}


/*
 * SHOW command
 */
void
ShowGUCConfigOption(const char *name)
{
	struct config_generic *record;

	record = find_option(name);
	if (record == NULL)
		elog(ERROR, "Option '%s' is not recognized", name);

	_ShowOption(record);
}

/*
 * SHOW ALL command
 */
void
ShowAllGUCConfig(void)
{
	int			i;

	for (i = 0; i < num_guc_variables; i++)
	{
		struct config_generic *conf = guc_variables[i];

		if ((conf->flags & GUC_NO_SHOW_ALL) == 0)
			_ShowOption(conf);
	}
}

static void
_ShowOption(struct config_generic *record)
{
	char		buffer[256];
	const char *val;

	switch (record->vartype)
	{
		case PGC_BOOL:
			{
				struct config_bool *conf = (struct config_bool *) record;

				if (conf->show_hook)
					val = (*conf->show_hook) ();
				else
					val = *conf->variable ? "on" : "off";
			}
			break;

		case PGC_INT:
			{
				struct config_int *conf = (struct config_int *) record;

				if (conf->show_hook)
					val = (*conf->show_hook) ();
				else
				{
					snprintf(buffer, sizeof(buffer), "%d",
							 *conf->variable);
					val = buffer;
				}
			}
			break;

		case PGC_REAL:
			{
				struct config_real *conf = (struct config_real *) record;

				if (conf->show_hook)
					val = (*conf->show_hook) ();
				else
				{
					snprintf(buffer, sizeof(buffer), "%g",
							 *conf->variable);
					val = buffer;
				}
			}
			break;

		case PGC_STRING:
			{
				struct config_string *conf = (struct config_string *) record;

				if (conf->show_hook)
					val = (*conf->show_hook) ();
				else if (*conf->variable && **conf->variable)
					val = *conf->variable;
				else
					val = "unset";
			}
			break;

		default:
			/* just to keep compiler quiet */
			val = "???";
			break;
	}

	elog(INFO, "%s is %s", record->name, val);
}


/*
 * A little "long argument" simulation, although not quite GNU
 * compliant. Takes a string of the form "some-option=some value" and
 * returns name = "some_option" and value = "some value" in malloc'ed
 * storage. Note that '-' is converted to '_' in the option name. If
 * there is no '=' in the input string then value will be NULL.
 */
void
ParseLongOption(const char *string, char **name, char **value)
{
	size_t		equal_pos;
	char	   *cp;

	AssertArg(string);
	AssertArg(name);
	AssertArg(value);

	equal_pos = strcspn(string, "=");

	if (string[equal_pos] == '=')
	{
		*name = malloc(equal_pos + 1);
		if (!*name)
			elog(FATAL, "out of memory");
		strncpy(*name, string, equal_pos);
		(*name)[equal_pos] = '\0';

		*value = strdup(&string[equal_pos + 1]);
		if (!*value)
			elog(FATAL, "out of memory");
	}
	else
	{
		/* no equal sign in string */
		*name = strdup(string);
		if (!*name)
			elog(FATAL, "out of memory");
		*value = NULL;
	}

	for (cp = *name; *cp; cp++)
		if (*cp == '-')
			*cp = '_';
}



#ifdef HAVE_SYSLOG

static const char *
assign_facility(const char *facility, bool doit, bool interactive)
{
	if (strcasecmp(facility, "LOCAL0") == 0)
		return facility;
	if (strcasecmp(facility, "LOCAL1") == 0)
		return facility;
	if (strcasecmp(facility, "LOCAL2") == 0)
		return facility;
	if (strcasecmp(facility, "LOCAL3") == 0)
		return facility;
	if (strcasecmp(facility, "LOCAL4") == 0)
		return facility;
	if (strcasecmp(facility, "LOCAL5") == 0)
		return facility;
	if (strcasecmp(facility, "LOCAL6") == 0)
		return facility;
	if (strcasecmp(facility, "LOCAL7") == 0)
		return facility;
	return NULL;
}

#endif


static const char *
assign_defaultxactisolevel(const char *newval, bool doit, bool interactive)
{
	if (strcasecmp(newval, "serializable") == 0)
		{ if (doit) DefaultXactIsoLevel = XACT_SERIALIZABLE; }
	else if (strcasecmp(newval, "read committed") == 0)
		{ if (doit) DefaultXactIsoLevel = XACT_READ_COMMITTED; }
	else
		return NULL;
	return newval;
}


/*
 * Handle options fetched from pg_database.datconfig or pg_shadow.useconfig.
 */
void
ProcessGUCArray(ArrayType *array, GucSource source)
{
	int		i;

	Assert(array != NULL);
	Assert(source == PGC_S_DATABASE || source == PGC_S_USER);

	for (i = 1; i <= ARR_DIMS(array)[0]; i++)
	{
		Datum		d;
		bool		isnull;
		char	   *s;
		char	   *name;
		char	   *value;

		d = array_ref(array, 1, &i,
					  false /*notbyvalue*/,
					  -1 /*varlenelem*/,
					  -1 /*varlenarray*/,
					  &isnull);

		if (isnull)
			continue;

		s = DatumGetCString(DirectFunctionCall1(textout, d));

		ParseLongOption(s, &name, &value);
		if (!value)
		{
			elog(WARNING, "cannot parse setting \"%s\"", name);
			free(name);
			continue;
		}

		/*
		 * We process all these options at SUSET level.  We assume that the
		 * right to insert an option into pg_database or pg_shadow was
		 * checked when it was inserted.
		 */
		SetConfigOption(name, value, PGC_SUSET, source);

		free(name);
		if (value)
			free(value);
	}
}



ArrayType *
GUCArrayAdd(ArrayType *array, const char *name, const char *value)
{
	Datum		datum;
	char	   *newval;
	ArrayType  *a;

	Assert(name);
	Assert(value);

	/* test if the option is valid */
	set_config_option(name, value,
					  superuser() ? PGC_SUSET : PGC_USERSET,
					  PGC_S_SESSION, false, false);

	newval = palloc(strlen(name) + 1 + strlen(value) + 1);
	sprintf(newval, "%s=%s", name, value);
	datum = DirectFunctionCall1(textin, CStringGetDatum(newval));

	if (array)
	{
		int		index;
		bool	isnull;
		int		i;

		index = ARR_DIMS(array)[0] + 1;	/* add after end */

		for (i = 1; i <= ARR_DIMS(array)[0]; i++)
		{
			Datum		d;
			char	   *current;

			d = array_ref(array, 1, &i,
						  false /*notbyvalue*/,
						  -1 /*varlenelem*/,
						  -1 /*varlenarray*/,
						  &isnull);
			current = DatumGetCString(DirectFunctionCall1(textout, d));
			if (strncmp(current, newval, strlen(name) + 1)==0)
			{
				index = i;
				break;
			}
		}

		isnull = false;
		a = array_set(array, 1, &index, datum, false/*notbyval*/, -1, -1, &isnull);
	}
	else
		a = construct_array(&datum, 1, false, -1, 'i');

	return a;
}



ArrayType *
GUCArrayDelete(ArrayType *array, const char *name)
{
	ArrayType *newarray;
	int i;
	int index;

	Assert(name);
	Assert(array);

	/* test if the option is valid */
	set_config_option(name, NULL,
					  superuser() ? PGC_SUSET : PGC_USERSET,
					  PGC_S_SESSION, false, false);

	newarray = construct_array(NULL, 0, false, -1, 'i');
	index = 1;

	for (i = 1; i <= ARR_DIMS(array)[0]; i++)
	{
		Datum		d;
		char	   *val;
		bool		isnull;

		d = array_ref(array, 1, &i,
					  false /*notbyvalue*/,
					  -1 /*varlenelem*/,
					  -1 /*varlenarray*/,
					  &isnull);
		val = DatumGetCString(DirectFunctionCall1(textout, d));

		if (strncmp(val, name, strlen(name))==0
			&& val[strlen(name)] == '=')
			continue;

		isnull = false;
		newarray = array_set(newarray, 1, &index, d, false/*notbyval*/, -1, -1, &isnull);
		index++;
	}

	return newarray;
}
