Make configuration parameters fall back to their default values when they

are removed from the configuration file.

Joachim Wieland

src/backend/utils/misc/guc-file.l

@@ -4,7 +4,7 @@
  *
  * Copyright (c) 2000-2007, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/backend/utils/misc/guc-file.l,v 1.49 2007/03/13 14:32:25 petere Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/misc/guc-file.l,v 1.50 2007/04/21 20:02:40 petere Exp $
  */
 
 %{
@@ -116,6 +116,9 @@ ProcessConfigFile(GucContext context)
 {
 	int			elevel;
 	struct name_value_pair *item, *head, *tail;
+	int			i;
+	bool	   *in_conffile = NULL;
+	const char *var;
 
 	Assert(context == PGC_POSTMASTER || context == PGC_SIGHUP);
 
@@ -140,19 +143,158 @@ ProcessConfigFile(GucContext context)
 	/* Check if all options are valid */
 	for (item = head; item; item = item->next)
 	{
+		char *sep = strchr(item->name, GUC_QUALIFIER_SEPARATOR);
+		if (sep && !is_custom_class(item->name, sep - item->name))
+		{
+			ereport(elevel,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("unrecognized configuration parameter \"%s\"",
+						item->name)));
+			goto cleanup_list;
+		}
+
 		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. */
+
+	/*
+	 * Mark all variables as not showing up in the config file.  The
+	 * allocation has to take place after ParseConfigFile() since this
+	 * function can change num_guc_variables due to custom variables.
+	 * It would be easier to add a new field or status bit to struct
+	 * conf_generic, but that way we would expose internal information
+	 * that is just needed here in the following few lines.  The price
+	 * to pay for this separation are a few more loops over the set of
+	 * configuration options, but those are expected to be rather few
+	 * and we only have to pay the cost at SIGHUP.  We initialize
+	 * in_conffile only here because set_config_option() makes
+	 * guc_variables grow with custom variables.
+	 */
+	in_conffile = guc_malloc(elevel, num_guc_variables * sizeof(bool));
+	if (!in_conffile)
+		goto cleanup_list;
+	for (i = 0; i < num_guc_variables; i++)
+		in_conffile[i] = false;
+
 	for (item = head; item; item = item->next)
 	{
+		/*
+		 * After set_config_option() the variable name item->name is
+		 * known to exist.
+		 */
+		Assert(guc_get_index(item->name) >= 0);
+		in_conffile[guc_get_index(item->name)] = true;
+	}
+
+	for (i = 0; i < num_guc_variables; i++)
+	{
+		struct config_generic *gconf = guc_variables[i];
+		if (!in_conffile[i] && gconf->source == PGC_S_FILE)
+		{
+			if (gconf->context < PGC_SIGHUP)
+				ereport(elevel,
+					(errcode(ERRCODE_CANT_CHANGE_RUNTIME_PARAM),
+							 errmsg("parameter \"%s\" cannot be changed after server start; configuration file change ignored",
+									gconf->name)));
+			else
+			{
+					/* prepare */
+					GucStack   *stack;
+					if (gconf->reset_source == PGC_S_FILE)
+						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;
+					/* apply the default */
+					set_config_option(gconf->name, NULL, context,
+									  PGC_S_DEFAULT, false, true);
+			}
+		}
+		else if (!in_conffile[i] && gconf->reset_source == PGC_S_FILE)
+		{
+			/*------
+			 * Change the reset_val to default_val.  Here's an
+			 * example: In the configuration file we have
+			 *
+			 * seq_page_cost = 3.00
+			 *
+			 * Now we execute in a session
+			 *
+			 * SET seq_page_cost TO 4.00;
+			 *
+			 * Then we remove this option from the configuration file
+			 * and send SIGHUP. Now when you execute
+			 *
+			 * RESET seq_page_cost;
+			 *
+			 * it should fall back to 1.00 (the default value for
+			 * seq_page_cost) and not to 3.00 (which is the current
+			 * reset_val).
+			 */
+
+			switch (gconf->vartype)
+			{
+				case PGC_BOOL:
+					{
+						struct config_bool *conf;
+						conf = (struct config_bool *) gconf;
+						conf->reset_val = conf->boot_val;
+						break;
+					}
+				case PGC_INT:
+					{
+						struct config_int *conf;
+						conf = (struct config_int *) gconf;
+						conf->reset_val = conf->boot_val;
+						break;
+					}
+				case PGC_REAL:
+					{
+						struct config_real *conf;
+						conf = (struct config_real *) gconf;
+						conf->reset_val = conf->boot_val;
+						break;
+					}
+				case PGC_STRING:
+					{
+						struct config_string   *conf;
+						conf = (struct config_string *) gconf;
+						/*
+						 * We can cast away the const here because we
+						 * won't free the address.  It is protected by
+						 * set_string_field() and string_field_used().
+						 */
+						conf->reset_val = (char *) conf->boot_val;
+						break;
+					}
+			}
+		}
+	}
+
+	/* If we got here all the options checked out okay, so apply them. */
+	for (item = head; item; item = item->next)
 		set_config_option(item->name, item->value, context,
 						  PGC_S_FILE, false, true);
-	}
+
+	/*
+	 * Reset variables to the value of environment variables
+	 * (PGC_S_ENV_VAR overrules PGC_S_FILE).  PGPORT is ignored,
+	 * because it cannot be changed without restart.
+	 */
+	var = getenv("PGDATESTYLE");
+	if (var != NULL)
+		set_config_option("datestyle", var, context,
+						  PGC_S_ENV_VAR, false, true);
+
+	var = getenv("PGCLIENTENCODING");
+	if (var != NULL)
+		set_config_option("client_encoding", var, context,
+						  PGC_S_ENV_VAR, false, true);
 
  cleanup_list:
+	free(in_conffile);
 	free_name_value_list(head);
 }
 
@@ -312,14 +454,14 @@ ParseConfigFile(const char *config_file, const char *calling_file,
 			{
 				pfree(opt_name);
 				pfree(opt_value);
-				/* we assume error message was logged already */
+
+				/* We assume the error message was logged already. */
 				OK = false;
 				goto cleanup_exit;
 			}
-			pfree(opt_name);
-			pfree(opt_value);
 		}
-		else
+
+		if (pg_strcasecmp(opt_name, "include") != 0)
 		{
 			/* append to list */
 			struct name_value_pair *item;

src/backend/utils/misc/guc.c

@@ -10,7 +10,7 @@
  * Written by Peter Eisentraut <peter_e@gmx.net>.
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.386 2007/04/18 16:44:18 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.387 2007/04/21 20:02:40 petere Exp $
  *
  *--------------------------------------------------------------------
  */
@@ -2481,7 +2481,8 @@ set_string_field(struct config_string * conf, char **field, char *newval)
 	if (oldval == NULL ||
 		oldval == *(conf->variable) ||
 		oldval == conf->reset_val ||
-		oldval == conf->tentative_val)
+		oldval == conf->tentative_val ||
+		oldval == conf->boot_val)
 		return;
 	for (stack = conf->gen.stack; stack; stack = stack->prev)
 	{
@@ -2504,7 +2505,8 @@ string_field_used(struct config_string * conf, char *strval)
 
 	if (strval == *(conf->variable) ||
 		strval == conf->reset_val ||
-		strval == conf->tentative_val)
+		strval == conf->tentative_val ||
+		strval == conf->boot_val)
 		return true;
 	for (stack = conf->gen.stack; stack; stack = stack->prev)
 	{
@@ -2673,6 +2675,18 @@ add_guc_variable(struct config_generic * var, int elevel)
 	return true;
 }
 
+static int
+guc_get_index(const char *name)
+{
+	int i;
+
+	for (i = 0; i < num_guc_variables; i++)
+		if (strcasecmp(name, guc_variables[i]->name) == 0)
+			return i;
+
+	return -1;
+}
+
 /*
  * Create and add a placeholder variable. It's presumed to belong
  * to a valid custom variable class at this point.
@@ -2851,39 +2865,39 @@ InitializeGUCOptions(void)
 					struct config_bool *conf = (struct config_bool *) gconf;
 
 					if (conf->assign_hook)
-						if (!(*conf->assign_hook) (conf->reset_val, true,
+						if (!(*conf->assign_hook) (conf->boot_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;
+								 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->reset_val >= conf->min);
-					Assert(conf->reset_val <= conf->max);
+					Assert(conf->boot_val >= conf->min);
+					Assert(conf->boot_val <= conf->max);
 					if (conf->assign_hook)
-						if (!(*conf->assign_hook) (conf->reset_val, true,
+						if (!(*conf->assign_hook) (conf->boot_val, true,
 												   PGC_S_DEFAULT))
 							elog(FATAL, "failed to initialize %s to %d",
-								 conf->gen.name, conf->reset_val);
-					*conf->variable = conf->reset_val;
+								 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->reset_val >= conf->min);
-					Assert(conf->reset_val <= conf->max);
+					Assert(conf->boot_val >= conf->min);
+					Assert(conf->boot_val <= conf->max);
 					if (conf->assign_hook)
-						if (!(*conf->assign_hook) (conf->reset_val, true,
+						if (!(*conf->assign_hook) (conf->boot_val, true,
 												   PGC_S_DEFAULT))
 							elog(FATAL, "failed to initialize %s to %g",
-								 conf->gen.name, conf->reset_val);
-					*conf->variable = conf->reset_val;
+								 conf->gen.name, conf->boot_val);
+					*conf->variable = conf->reset_val = conf->boot_val; 
 					break;
 				}
 			case PGC_STRING:
@@ -3945,6 +3959,13 @@ set_config_option(const char *name, const char *value,
 		return false;
 	}
 
+	/*
+	 * Do not replace a value that has been set on the command line by a SIGHUP
+	 * reload
+	 */
+	if (context == PGC_SIGHUP && record->source == PGC_S_ARGV)
+		return true;
+
 	/*
 	 * 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
@@ -4040,19 +4061,26 @@ set_config_option(const char *name, const char *value,
 	}
 
 	/*
-	 * Should we set reset/stacked values?	(If so, the behavior is not
-	 * transactional.)
+	 * Should we set reset/stacked values?  (If so, the behavior is not
+	 * transactional.)  This is done either when we get a default
+	 * value from the database's/user's/client's default settings or
+	 * when we reset a value to its default.
 	 */
-	makeDefault = changeVal && (source <= PGC_S_OVERRIDE) && (value != NULL);
+	makeDefault = changeVal && (source <= PGC_S_OVERRIDE)
+					&& ((value != NULL) || source == PGC_S_DEFAULT);
 
 	/*
-	 * Ignore attempted set if overridden by previously processed setting.
-	 * However, if changeVal 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/stacked values even if we can't set the variable itself.
+	 * Ignore attempted set if overridden by previously processed
+	 * setting.  However, if changeVal 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/stacked values even if
+	 * we can't set the variable itself.  There's one exception to
+	 * this rule: if we want to apply the default value to variables
+	 * that were removed from the configuration file.  This is
+	 * indicated by source == PGC_S_DEFAULT.
 	 */
-	if (record->source > source)
+	if (record->source > source && source != PGC_S_DEFAULT)
 	{
 		if (changeVal && !makeDefault)
 		{
@@ -4084,6 +4112,14 @@ set_config_option(const char *name, const char *value,
 						return false;
 					}
 				}
+				/*
+				 * If value == NULL and source == PGC_S_DEFAULT then
+				 * we reset some value to its default (removed from
+				 * configuration file).
+				 */
+				else if (source == PGC_S_DEFAULT)
+					newval = conf->boot_val;
+				/* else we handle a "RESET varname" command */
 				else
 				{
 					newval = conf->reset_val;
@@ -4168,6 +4204,14 @@ set_config_option(const char *name, const char *value,
 						return false;
 					}
 				}
+				/*
+				 * If value == NULL and source == PGC_S_DEFAULT then
+				 * we reset some value to its default (removed from
+				 * configuration file).
+				 */
+				else if (source == PGC_S_DEFAULT)
+					newval = conf->boot_val;
+				/* else we handle a "RESET varname" command */
 				else
 				{
 					newval = conf->reset_val;
@@ -4252,6 +4296,14 @@ set_config_option(const char *name, const char *value,
 						return false;
 					}
 				}
+				/*
+				 * If value == NULL and source == PGC_S_DEFAULT then
+				 * we reset some value to its default (removed from
+				 * configuration file).
+				 */
+				else if (source == PGC_S_DEFAULT)
+					newval = conf->boot_val;
+				/* else we handle a "RESET varname" command */
 				else
 				{
 					newval = conf->reset_val;
@@ -4330,6 +4382,23 @@ set_config_option(const char *name, const char *value,
 					if (conf->gen.flags & GUC_IS_NAME)
 						truncate_identifier(newval, strlen(newval), true);
 				}
+				/*
+				 * If value == NULL and source == PGC_S_DEFAULT then
+				 * we reset some value to its default (removed from
+				 * configuration file).
+				 */
+				else if (source == PGC_S_DEFAULT)
+				{
+					if (conf->boot_val == NULL)
+						newval = NULL;
+					else
+					{
+						newval = guc_strdup(elevel, conf->boot_val);
+						if (newval == NULL)
+							return false;
+					}
+				}
+				/* else we handle a "RESET varname" command */
 				else if (conf->reset_val)
 				{
 					/*
@@ -6404,6 +6473,13 @@ assign_custom_variable_classes(const char *newval, bool doit, GucSource source)
 	int			c;
 	StringInfoData buf;
 
+	/*
+	 * Resetting custom_variable_classes by removing it from the
+	 * configuration file will lead to newval = NULL
+	 */
+	if (newval == NULL)
+		return guc_strdup(ERROR, "");
+
 	initStringInfo(&buf);
 	while ((c = *cp++) != 0)
 	{
@@ -6448,7 +6524,7 @@ assign_custom_variable_classes(const char *newval, bool doit, GucSource source)
 	if (buf.len == 0)
 		newval = NULL;
 	else if (doit)
-		newval = strdup(buf.data);
+		newval = guc_strdup(ERROR, buf.data);
 
 	pfree(buf.data);
 	return newval;

src/include/utils/guc_tables.h

@@ -7,7 +7,7 @@
  *
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  *
- *	  $PostgreSQL: pgsql/src/include/utils/guc_tables.h,v 1.32 2007/03/13 14:32:25 petere Exp $
+ *	  $PostgreSQL: pgsql/src/include/utils/guc_tables.h,v 1.33 2007/04/21 20:02:41 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -154,10 +154,11 @@ struct config_bool
 	/* these fields must be set correctly in initial value: */
 	/* (all but reset_val are constants) */
 	bool	   *variable;
-	bool		reset_val;
+	bool		boot_val;
 	GucBoolAssignHook assign_hook;
 	GucShowHook show_hook;
 	/* variable fields, initialized at runtime: */
+	bool		reset_val;
 	bool		tentative_val;
 };
 
@@ -167,12 +168,13 @@ struct config_int
 	/* these fields must be set correctly in initial value: */
 	/* (all but reset_val are constants) */
 	int		   *variable;
-	int			reset_val;
+	int			boot_val;
 	int			min;
 	int			max;
 	GucIntAssignHook assign_hook;
 	GucShowHook show_hook;
 	/* variable fields, initialized at runtime: */
+	int			reset_val;
 	int			tentative_val;
 };
 
@@ -182,12 +184,13 @@ struct config_real
 	/* these fields must be set correctly in initial value: */
 	/* (all but reset_val are constants) */
 	double	   *variable;
-	double		reset_val;
+	double		boot_val;
 	double		min;
 	double		max;
 	GucRealAssignHook assign_hook;
 	GucShowHook show_hook;
 	/* variable fields, initialized at runtime: */
+	double		reset_val;
 	double		tentative_val;
 };