Remove the custom_variable_classes parameter.

This variable provides only marginal error-prevention capability (since
it can only check the prefix of a qualified GUC name), and the consensus
is that that isn't worth the amount of hassle that maintaining the setting
creates for DBAs.  So, let's just remove it.

With this commit, the system will silently accept a value for any qualified
GUC name at all, whether it has anything to do with any known extension or
not.  (Unqualified names still have to match known built-in settings,
though; and you will get a WARNING at extension load time if there's an
unrecognized setting with that extension's prefix.)

There's still some discussion ongoing about whether to tighten that up and
if so how; but if we do come up with a solution, it's not likely to look
anything like custom_variable_classes.

9 files changed, 31 insertions, 256 deletions

diff --git a/src/backend/utils/misc/guc-file.l b/src/backend/utils/misc/guc-file.l
index a7cf0378dc..7728544c54 100644
--- a/src/backend/utils/misc/guc-file.l
+++ b/src/backend/utils/misc/guc-file.l
@@ -111,8 +111,6 @@ ProcessConfigFile(GucContext context)
 	ConfigVariable *item,
 				   *head,
 				   *tail;
-	char	   *cvc = NULL;
-	struct config_string *cvc_struct;
 	int			i;
 
 	/*
@@ -139,50 +137,6 @@ ProcessConfigFile(GucContext context)
 	}
 
 	/*
-	 * We need the proposed new value of custom_variable_classes to check
-	 * custom variables with.  ParseConfigFile ensured that if it's in
-	 * the file, it's first in the list.  But first check to see if we
-	 * have an active value from the command line, which should override
-	 * the file in any case.  (Since there's no relevant env var, the
-	 * only possible nondefault sources are the file and ARGV.)
-	 */
-	cvc_struct = (struct config_string *)
-		find_option("custom_variable_classes", false, elevel);
-	Assert(cvc_struct);
-	if (cvc_struct->gen.reset_source > PGC_S_FILE)
-	{
-		cvc = guc_strdup(elevel, cvc_struct->reset_val);
-		if (cvc == NULL)
-		{
-			error = true;
-			goto cleanup_list;
-		}
-	}
-	else if (head != NULL &&
-			 guc_name_compare(head->name, "custom_variable_classes") == 0)
-	{
-		/*
-		 * Need to canonicalize the value by calling the check hook.
-		 */
-		void   *extra = NULL;
-
-		cvc = guc_strdup(elevel, head->value);
-		if (cvc == NULL)
-		{
-			error = true;
-			goto cleanup_list;
-		}
-		if (!call_string_check_hook(cvc_struct, &cvc, &extra,
-									PGC_S_FILE, elevel))
-		{
-			error = true;
-			goto cleanup_list;
-		}
-		if (extra)
-			free(extra);
-	}
-
-	/*
 	 * Mark all extant GUC variables as not present in the config file.
 	 * We need this so that we can tell below which ones have been removed
 	 * from the file since we last processed it.
@@ -199,39 +153,29 @@ ProcessConfigFile(GucContext context)
 	 * quasi-syntactic check on the validity of the config file.  It is
 	 * important that the postmaster and all backends agree on the results
 	 * of this phase, else we will have strange inconsistencies about which
-	 * processes accept a config file update and which don't.  Hence, custom
-	 * variable names can only be checked against custom_variable_classes,
-	 * not against any loadable modules that might (or might not) be present.
-	 * Likewise, we don't attempt to validate the options' values here.
+	 * processes accept a config file update and which don't.  Hence, unknown
+	 * custom variable names have to be accepted without complaint.  For the
+	 * same reason, we don't attempt to validate the options' values here.
 	 *
 	 * In addition, the GUC_IS_IN_FILE flag is set on each existing GUC
 	 * variable mentioned in the file.
 	 */
 	for (item = head; item; item = item->next)
 	{
-		char   *sep = strchr(item->name, GUC_QUALIFIER_SEPARATOR);
 		struct config_generic *record;
 
-		if (sep)
-		{
-			/* Custom variable, so check against custom_variable_classes */
-			if (!is_custom_class(item->name, sep - item->name, cvc))
-			{
-				ereport(elevel,
-						(errcode(ERRCODE_UNDEFINED_OBJECT),
-						 errmsg("unrecognized configuration parameter \"%s\" in file \"%s\" line %u",
-								item->name,
-								item->filename, item->sourceline)));
-				error = true;
-				continue;
-			}
-		}
-
+		/*
+		 * Try to find the variable; but do not create a custom placeholder
+		 * if it's not there already.
+		 */
 		record = find_option(item->name, false, elevel);
 
 		if (record)
+		{
+			/* Found, so mark it as present in file */
 			record->status |= GUC_IS_IN_FILE;
-		else if (!sep)
+		}
+		else if (strchr(item->name, GUC_QUALIFIER_SEPARATOR) == NULL)
 		{
 			/* Invalid non-custom variable, so complain */
 			ereport(elevel,
@@ -382,8 +326,6 @@ ProcessConfigFile(GucContext context)
 
  cleanup_list:
 	FreeConfigVariables(head);
-	if (cvc)
-		free(cvc);
 
 	if (error)
 	{
@@ -581,40 +523,6 @@ ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
 			pfree(opt_name);
 			pfree(opt_value);
 		}
-		else if (guc_name_compare(opt_name, "custom_variable_classes") == 0)
-		{
-			/*
-			 * This variable must be processed first as it controls
-			 * the validity of other variables; so it goes at the head
-			 * of the result list.  If we already found a value for it,
-			 * replace with this one.
-			 */
-			item = *head_p;
-			if (item != NULL &&
-				guc_name_compare(item->name, "custom_variable_classes") == 0)
-			{
-				/* replace existing head item */
-				pfree(item->name);
-				pfree(item->value);
-				item->name = opt_name;
-				item->value = opt_value;
-				item->filename = pstrdup(config_file);
-				item->sourceline = ConfigFileLineno-1;
-			}
-			else
-			{
-				/* prepend to list */
-				item = palloc(sizeof *item);
-				item->name = opt_name;
-				item->value = opt_value;
-				item->filename = pstrdup(config_file);
-				item->sourceline = ConfigFileLineno-1;
-				item->next = *head_p;
-				*head_p = item;
-				if (*tail_p == NULL)
-					*tail_p = item;
-			}
-		}
 		else
 		{
 			/* ordinary variable, append to list */
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index c5b14522d5..2fd4867d25 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -178,7 +178,6 @@ static void assign_syslog_ident(const char *newval, void *extra);
 static void assign_session_replication_role(int newval, void *extra);
 static bool check_temp_buffers(int *newval, void **extra, GucSource source);
 static bool check_phony_autocommit(bool *newval, void **extra, GucSource source);
-static bool check_custom_variable_classes(char **newval, void **extra, GucSource source);
 static bool check_debug_assertions(bool *newval, void **extra, GucSource source);
 static bool check_bonjour(bool *newval, void **extra, GucSource source);
 static bool check_ssl(bool *newval, void **extra, GucSource source);
@@ -467,7 +466,6 @@ static char *log_timezone_string;
 static char *timezone_abbreviations_string;
 static char *XactIsoLevel_string;
 static char *session_authorization_string;
-static char *custom_variable_classes;
 static int	max_function_args;
 static int	max_index_keys;
 static int	max_identifier_length;
@@ -2886,17 +2884,6 @@ static struct config_string ConfigureNamesString[] =
 	},
 
 	{
-		{"custom_variable_classes", PGC_SIGHUP, CUSTOM_OPTIONS,
-			gettext_noop("Sets the list of known custom variable classes."),
-			NULL,
-			GUC_LIST_INPUT | GUC_LIST_QUOTE
-		},
-		&custom_variable_classes,
-		NULL,
-		check_custom_variable_classes, NULL, NULL
-	},
-
-	{
 		{"data_directory", PGC_POSTMASTER, FILE_LOCATIONS,
 			gettext_noop("Sets the server's data directory."),
 			NULL,
@@ -3623,8 +3610,7 @@ add_guc_variable(struct config_generic * var, int elevel)
 }
 
 /*
- * Create and add a placeholder variable. It's presumed to belong
- * to a valid custom variable class at this point.
+ * Create and add a placeholder variable for a custom variable name.
  */
 static struct config_generic *
 add_placeholder_variable(const char *name, int elevel)
@@ -3670,42 +3656,6 @@ add_placeholder_variable(const char *name, int elevel)
 }
 
 /*
- * Detect whether the portion of "name" before dotPos matches any custom
- * variable class name listed in custom_var_classes.  The latter must be
- * formatted the way that assign_custom_variable_classes does it, ie,
- * no whitespace.  NULL is valid for custom_var_classes.
- */
-static bool
-is_custom_class(const char *name, int dotPos, const char *custom_var_classes)
-{
-	bool		result = false;
-	const char *ccs = custom_var_classes;
-
-	if (ccs != NULL)
-	{
-		const char *start = ccs;
-
-		for (;; ++ccs)
-		{
-			char		c = *ccs;
-
-			if (c == '\0' || c == ',')
-			{
-				if (dotPos == ccs - start && strncmp(start, name, dotPos) == 0)
-				{
-					result = true;
-					break;
-				}
-				if (c == '\0')
-					break;
-				start = ccs + 1;
-			}
-		}
-	}
-	return result;
-}
-
-/*
  * Look up option NAME.  If it exists, return a pointer to its record,
  * else return NULL.  If create_placeholders is TRUE, we'll create a
  * placeholder record for a valid-looking custom variable name.
@@ -3745,13 +3695,9 @@ find_option(const char *name, bool create_placeholders, int elevel)
 	if (create_placeholders)
 	{
 		/*
-		 * Check if the name is qualified, and if so, check if the qualifier
-		 * matches any custom variable class.  If so, add a placeholder.
+		 * Check if the name is qualified, and if so, add a placeholder.
 		 */
-		const char *dot = strchr(name, GUC_QUALIFIER_SEPARATOR);
-
-		if (dot != NULL &&
-			is_custom_class(name, dot - name, custom_variable_classes))
+		if (strchr(name, GUC_QUALIFIER_SEPARATOR) != NULL)
 			return add_placeholder_variable(name, elevel);
 	}
 
@@ -7406,7 +7352,6 @@ write_nondefault_variables(GucContext context)
 {
 	int			elevel;
 	FILE	   *fp;
-	struct config_generic *cvc_conf;
 	int			i;
 
 	Assert(context == PGC_POSTMASTER || context == PGC_SIGHUP);
@@ -7426,20 +7371,9 @@ write_nondefault_variables(GucContext context)
 		return;
 	}
 
-	/*
-	 * custom_variable_classes must be written out first; otherwise we might
-	 * reject custom variable values while reading the file.
-	 */
-	cvc_conf = find_option("custom_variable_classes", false, ERROR);
-	if (cvc_conf)
-		write_one_nondefault_variable(fp, cvc_conf);
-
 	for (i = 0; i < num_guc_variables; i++)
 	{
-		struct config_generic *gconf = guc_variables[i];
-
-		if (gconf != cvc_conf)
-			write_one_nondefault_variable(fp, gconf);
+		write_one_nondefault_variable(fp, guc_variables[i]);
 	}
 
 	if (FreeFile(fp))
@@ -7886,20 +7820,15 @@ validate_option_array_item(const char *name, const char *value,
 	 * permissions normally (ie, allow if variable is USERSET, or if it's
 	 * SUSET and user is superuser).
 	 *
-	 * name is not known, but exists or can be created as a placeholder
-	 * (implying it has a prefix listed in custom_variable_classes). We allow
-	 * this case if you're a superuser, otherwise not.  Superusers are assumed
-	 * to know what they're doing.  We can't allow it for other users, because
-	 * when the placeholder is resolved it might turn out to be a SUSET
-	 * variable; define_custom_variable assumes we checked that.
+	 * name is not known, but exists or can be created as a placeholder (i.e.,
+	 * it has a prefixed name).  We allow this case if you're a superuser,
+	 * otherwise not.  Superusers are assumed to know what they're doing.
+	 * We can't allow it for other users, because when the placeholder is
+	 * resolved it might turn out to be a SUSET variable;
+	 * define_custom_variable assumes we checked that.
 	 *
 	 * name is not known and can't be created as a placeholder.  Throw error,
-	 * unless skipIfNoPermissions is true, in which case return FALSE. (It's
-	 * tempting to allow this case to superusers, if the name is qualified but
-	 * not listed in custom_variable_classes.  That would ease restoring of
-	 * dumps containing ALTER ROLE/DATABASE SET.  However, it's not clear that
-	 * this usage justifies such a loss of error checking. You can always fix
-	 * custom_variable_classes before you restore.)
+	 * unless skipIfNoPermissions is true, in which case return FALSE.
 	 */
 	gconf = find_option(name, true, WARNING);
 	if (!gconf)
@@ -7909,7 +7838,8 @@ validate_option_array_item(const char *name, const char *value,
 			return false;
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_OBJECT),
-			   errmsg("unrecognized configuration parameter \"%s\"", name)));
+				 errmsg("unrecognized configuration parameter \"%s\"",
+						name)));
 	}
 
 	if (gconf->flags & GUC_CUSTOM_PLACEHOLDER)
@@ -8263,69 +8193,6 @@ check_phony_autocommit(bool *newval, void **extra, GucSource source)
 }
 
 static bool
-check_custom_variable_classes(char **newval, void **extra, GucSource source)
-{
-	/*
-	 * Check syntax. newval must be a comma separated list of identifiers.
-	 * Whitespace is allowed but removed from the result.
-	 */
-	bool		hasSpaceAfterToken = false;
-	const char *cp = *newval;
-	int			symLen = 0;
-	char		c;
-	StringInfoData buf;
-
-	/* Default NULL is OK */
-	if (cp == NULL)
-		return true;
-
-	initStringInfo(&buf);
-	while ((c = *cp++) != '\0')
-	{
-		if (isspace((unsigned char) c))
-		{
-			if (symLen > 0)
-				hasSpaceAfterToken = true;
-			continue;
-		}
-
-		if (c == ',')
-		{
-			if (symLen > 0)		/* terminate identifier */
-			{
-				appendStringInfoChar(&buf, ',');
-				symLen = 0;
-			}
-			hasSpaceAfterToken = false;
-			continue;
-		}
-
-		if (hasSpaceAfterToken || !(isalnum((unsigned char) c) || c == '_'))
-		{
-			/*
-			 * Syntax error due to token following space after token or
-			 * non-identifier character
-			 */
-			pfree(buf.data);
-			return false;
-		}
-		appendStringInfoChar(&buf, c);
-		symLen++;
-	}
-
-	/* Remove stray ',' at end */
-	if (symLen == 0 && buf.len > 0)
-		buf.data[--buf.len] = '\0';
-
-	/* GUC wants the result malloc'd */
-	free(*newval);
-	*newval = guc_strdup(LOG, buf.data);
-
-	pfree(buf.data);
-	return true;
-}
-
-static bool
 check_debug_assertions(bool *newval, void **extra, GucSource source)
 {
 #ifndef USE_ASSERT_CHECKING
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index a18f14ae25..5bb7e7117b 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -560,4 +560,4 @@
 # CUSTOMIZED OPTIONS
 #------------------------------------------------------------------------------
 
-#custom_variable_classes = ''		# list of custom variable class names
+# Add settings for extensions here
diff --git a/src/pl/plperl/expected/plperl_init.out b/src/pl/plperl/expected/plperl_init.out
index 4a04dbd6f3..e8a8e9bd83 100644
--- a/src/pl/plperl/expected/plperl_init.out
+++ b/src/pl/plperl/expected/plperl_init.out
@@ -1,5 +1,5 @@
 -- test plperl.on_plperl_init errors are fatal
--- Avoid need for custom_variable_classes = 'plperl'
+-- Must load plperl before we can set on_plperl_init
 LOAD 'plperl';
 SET SESSION plperl.on_plperl_init = ' system("/nonesuch") ';
 SHOW plperl.on_plperl_init;
diff --git a/src/pl/plperl/expected/plperl_shared.out b/src/pl/plperl/expected/plperl_shared.out
index 1a6bf5ee4d..67478ab454 100644
--- a/src/pl/plperl/expected/plperl_shared.out
+++ b/src/pl/plperl/expected/plperl_shared.out
@@ -1,6 +1,6 @@
 -- test plperl.on_plperl_init via the shared hash
 -- (must be done before plperl is first used)
--- Avoid need for custom_variable_classes = 'plperl'
+-- Must load plperl before we can set on_plperl_init
 LOAD 'plperl';
 -- testing on_plperl_init gets run, and that it can alter %_SHARED
 SET plperl.on_plperl_init = '$_SHARED{on_init} = 42';
diff --git a/src/pl/plperl/expected/plperlu.out b/src/pl/plperl/expected/plperlu.out
index 25ac007b7a..1ba07eed9d 100644
--- a/src/pl/plperl/expected/plperlu.out
+++ b/src/pl/plperl/expected/plperlu.out
@@ -1,6 +1,6 @@
 -- Use ONLY plperlu tests here. For plperl/plerlu combined tests
 -- see plperl_plperlu.sql
--- Avoid need for custom_variable_classes = 'plperl'
+-- Must load plperl before we can set on_plperlu_init
 LOAD 'plperl';
 -- Test plperl.on_plperlu_init gets run
 SET plperl.on_plperlu_init = '$_SHARED{init} = 42';
diff --git a/src/pl/plperl/sql/plperl_init.sql b/src/pl/plperl/sql/plperl_init.sql
index f6a32b9bae..51ac9192bd 100644
--- a/src/pl/plperl/sql/plperl_init.sql
+++ b/src/pl/plperl/sql/plperl_init.sql
@@ -1,6 +1,6 @@
 -- test plperl.on_plperl_init errors are fatal
 
--- Avoid need for custom_variable_classes = 'plperl'
+-- Must load plperl before we can set on_plperl_init
 LOAD 'plperl';
 
 SET SESSION plperl.on_plperl_init = ' system("/nonesuch") ';
diff --git a/src/pl/plperl/sql/plperl_shared.sql b/src/pl/plperl/sql/plperl_shared.sql
index d367d32ff0..d2fa8cbf93 100644
--- a/src/pl/plperl/sql/plperl_shared.sql
+++ b/src/pl/plperl/sql/plperl_shared.sql
@@ -1,7 +1,7 @@
 -- test plperl.on_plperl_init via the shared hash
 -- (must be done before plperl is first used)
 
--- Avoid need for custom_variable_classes = 'plperl'
+-- Must load plperl before we can set on_plperl_init
 LOAD 'plperl';
 
 -- testing on_plperl_init gets run, and that it can alter %_SHARED
diff --git a/src/pl/plperl/sql/plperlu.sql b/src/pl/plperl/sql/plperlu.sql
index 125691e5f7..831b8f4460 100644
--- a/src/pl/plperl/sql/plperlu.sql
+++ b/src/pl/plperl/sql/plperlu.sql
@@ -1,7 +1,7 @@
 -- Use ONLY plperlu tests here. For plperl/plerlu combined tests
 -- see plperl_plperlu.sql
 
--- Avoid need for custom_variable_classes = 'plperl'
+-- Must load plperl before we can set on_plperlu_init
 LOAD 'plperl';
 
 -- Test plperl.on_plperlu_init gets run