Adding upstream version 15.5.upstream/15.5

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 935 insertions, 0 deletions

diff --git a/src/backend/commands/variable.c b/src/backend/commands/variable.c
new file mode 100644
index 0000000..e5ddcda
--- /dev/null
+++ b/src/backend/commands/variable.c
@@ -0,0 +1,935 @@
+/*-------------------------------------------------------------------------
+ *
+ * variable.c
+ *		Routines for handling specialized SET variables.
+ *
+ *
+ * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/commands/variable.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <ctype.h>
+
+#include "access/htup_details.h"
+#include "access/parallel.h"
+#include "access/xact.h"
+#include "access/xlog.h"
+#include "catalog/pg_authid.h"
+#include "commands/variable.h"
+#include "mb/pg_wchar.h"
+#include "miscadmin.h"
+#include "utils/acl.h"
+#include "utils/builtins.h"
+#include "utils/snapmgr.h"
+#include "utils/syscache.h"
+#include "utils/timestamp.h"
+#include "utils/varlena.h"
+
+/*
+ * DATESTYLE
+ */
+
+/*
+ * check_datestyle: GUC check_hook for datestyle
+ */
+bool
+check_datestyle(char **newval, void **extra, GucSource source)
+{
+	int			newDateStyle = DateStyle;
+	int			newDateOrder = DateOrder;
+	bool		have_style = false;
+	bool		have_order = false;
+	bool		ok = true;
+	char	   *rawstring;
+	int		   *myextra;
+	char	   *result;
+	List	   *elemlist;
+	ListCell   *l;
+
+	/* Need a modifiable copy of string */
+	rawstring = pstrdup(*newval);
+
+	/* Parse string into list of identifiers */
+	if (!SplitIdentifierString(rawstring, ',', &elemlist))
+	{
+		/* syntax error in list */
+		GUC_check_errdetail("List syntax is invalid.");
+		pfree(rawstring);
+		list_free(elemlist);
+		return false;
+	}
+
+	foreach(l, elemlist)
+	{
+		char	   *tok = (char *) lfirst(l);
+
+		/* Ugh. Somebody ought to write a table driven version -- mjl */
+
+		if (pg_strcasecmp(tok, "ISO") == 0)
+		{
+			if (have_style && newDateStyle != USE_ISO_DATES)
+				ok = false;		/* conflicting styles */
+			newDateStyle = USE_ISO_DATES;
+			have_style = true;
+		}
+		else if (pg_strcasecmp(tok, "SQL") == 0)
+		{
+			if (have_style && newDateStyle != USE_SQL_DATES)
+				ok = false;		/* conflicting styles */
+			newDateStyle = USE_SQL_DATES;
+			have_style = true;
+		}
+		else if (pg_strncasecmp(tok, "POSTGRES", 8) == 0)
+		{
+			if (have_style && newDateStyle != USE_POSTGRES_DATES)
+				ok = false;		/* conflicting styles */
+			newDateStyle = USE_POSTGRES_DATES;
+			have_style = true;
+		}
+		else if (pg_strcasecmp(tok, "GERMAN") == 0)
+		{
+			if (have_style && newDateStyle != USE_GERMAN_DATES)
+				ok = false;		/* conflicting styles */
+			newDateStyle = USE_GERMAN_DATES;
+			have_style = true;
+			/* GERMAN also sets DMY, unless explicitly overridden */
+			if (!have_order)
+				newDateOrder = DATEORDER_DMY;
+		}
+		else if (pg_strcasecmp(tok, "YMD") == 0)
+		{
+			if (have_order && newDateOrder != DATEORDER_YMD)
+				ok = false;		/* conflicting orders */
+			newDateOrder = DATEORDER_YMD;
+			have_order = true;
+		}
+		else if (pg_strcasecmp(tok, "DMY") == 0 ||
+				 pg_strncasecmp(tok, "EURO", 4) == 0)
+		{
+			if (have_order && newDateOrder != DATEORDER_DMY)
+				ok = false;		/* conflicting orders */
+			newDateOrder = DATEORDER_DMY;
+			have_order = true;
+		}
+		else if (pg_strcasecmp(tok, "MDY") == 0 ||
+				 pg_strcasecmp(tok, "US") == 0 ||
+				 pg_strncasecmp(tok, "NONEURO", 7) == 0)
+		{
+			if (have_order && newDateOrder != DATEORDER_MDY)
+				ok = false;		/* conflicting orders */
+			newDateOrder = DATEORDER_MDY;
+			have_order = true;
+		}
+		else if (pg_strcasecmp(tok, "DEFAULT") == 0)
+		{
+			/*
+			 * Easiest way to get the current DEFAULT state is to fetch the
+			 * DEFAULT string from guc.c and recursively parse it.
+			 *
+			 * We can't simply "return check_datestyle(...)" because we need
+			 * to handle constructs like "DEFAULT, ISO".
+			 */
+			char	   *subval;
+			void	   *subextra = NULL;
+
+			subval = strdup(GetConfigOptionResetString("datestyle"));
+			if (!subval)
+			{
+				ok = false;
+				break;
+			}
+			if (!check_datestyle(&subval, &subextra, source))
+			{
+				free(subval);
+				ok = false;
+				break;
+			}
+			myextra = (int *) subextra;
+			if (!have_style)
+				newDateStyle = myextra[0];
+			if (!have_order)
+				newDateOrder = myextra[1];
+			free(subval);
+			free(subextra);
+		}
+		else
+		{
+			GUC_check_errdetail("Unrecognized key word: \"%s\".", tok);
+			pfree(rawstring);
+			list_free(elemlist);
+			return false;
+		}
+	}
+
+	pfree(rawstring);
+	list_free(elemlist);
+
+	if (!ok)
+	{
+		GUC_check_errdetail("Conflicting \"datestyle\" specifications.");
+		return false;
+	}
+
+	/*
+	 * Prepare the canonical string to return.  GUC wants it malloc'd.
+	 */
+	result = (char *) malloc(32);
+	if (!result)
+		return false;
+
+	switch (newDateStyle)
+	{
+		case USE_ISO_DATES:
+			strcpy(result, "ISO");
+			break;
+		case USE_SQL_DATES:
+			strcpy(result, "SQL");
+			break;
+		case USE_GERMAN_DATES:
+			strcpy(result, "German");
+			break;
+		default:
+			strcpy(result, "Postgres");
+			break;
+	}
+	switch (newDateOrder)
+	{
+		case DATEORDER_YMD:
+			strcat(result, ", YMD");
+			break;
+		case DATEORDER_DMY:
+			strcat(result, ", DMY");
+			break;
+		default:
+			strcat(result, ", MDY");
+			break;
+	}
+
+	free(*newval);
+	*newval = result;
+
+	/*
+	 * Set up the "extra" struct actually used by assign_datestyle.
+	 */
+	myextra = (int *) malloc(2 * sizeof(int));
+	if (!myextra)
+		return false;
+	myextra[0] = newDateStyle;
+	myextra[1] = newDateOrder;
+	*extra = (void *) myextra;
+
+	return true;
+}
+
+/*
+ * assign_datestyle: GUC assign_hook for datestyle
+ */
+void
+assign_datestyle(const char *newval, void *extra)
+{
+	int		   *myextra = (int *) extra;
+
+	DateStyle = myextra[0];
+	DateOrder = myextra[1];
+}
+
+
+/*
+ * TIMEZONE
+ */
+
+/*
+ * check_timezone: GUC check_hook for timezone
+ */
+bool
+check_timezone(char **newval, void **extra, GucSource source)
+{
+	pg_tz	   *new_tz;
+	long		gmtoffset;
+	char	   *endptr;
+	double		hours;
+
+	if (pg_strncasecmp(*newval, "interval", 8) == 0)
+	{
+		/*
+		 * Support INTERVAL 'foo'.  This is for SQL spec compliance, not
+		 * because it has any actual real-world usefulness.
+		 */
+		const char *valueptr = *newval;
+		char	   *val;
+		Interval   *interval;
+
+		valueptr += 8;
+		while (isspace((unsigned char) *valueptr))
+			valueptr++;
+		if (*valueptr++ != '\'')
+			return false;
+		val = pstrdup(valueptr);
+		/* Check and remove trailing quote */
+		endptr = strchr(val, '\'');
+		if (!endptr || endptr[1] != '\0')
+		{
+			pfree(val);
+			return false;
+		}
+		*endptr = '\0';
+
+		/*
+		 * Try to parse it.  XXX an invalid interval format will result in
+		 * ereport(ERROR), which is not desirable for GUC.  We did what we
+		 * could to guard against this in flatten_set_variable_args, but a
+		 * string coming in from postgresql.conf might contain anything.
+		 */
+		interval = DatumGetIntervalP(DirectFunctionCall3(interval_in,
+														 CStringGetDatum(val),
+														 ObjectIdGetDatum(InvalidOid),
+														 Int32GetDatum(-1)));
+
+		pfree(val);
+		if (interval->month != 0)
+		{
+			GUC_check_errdetail("Cannot specify months in time zone interval.");
+			pfree(interval);
+			return false;
+		}
+		if (interval->day != 0)
+		{
+			GUC_check_errdetail("Cannot specify days in time zone interval.");
+			pfree(interval);
+			return false;
+		}
+
+		/* Here we change from SQL to Unix sign convention */
+		gmtoffset = -(interval->time / USECS_PER_SEC);
+		new_tz = pg_tzset_offset(gmtoffset);
+
+		pfree(interval);
+	}
+	else
+	{
+		/*
+		 * Try it as a numeric number of hours (possibly fractional).
+		 */
+		hours = strtod(*newval, &endptr);
+		if (endptr != *newval && *endptr == '\0')
+		{
+			/* Here we change from SQL to Unix sign convention */
+			gmtoffset = -hours * SECS_PER_HOUR;
+			new_tz = pg_tzset_offset(gmtoffset);
+		}
+		else
+		{
+			/*
+			 * Otherwise assume it is a timezone name, and try to load it.
+			 */
+			new_tz = pg_tzset(*newval);
+
+			if (!new_tz)
+			{
+				/* Doesn't seem to be any great value in errdetail here */
+				return false;
+			}
+
+			if (!pg_tz_acceptable(new_tz))
+			{
+				GUC_check_errmsg("time zone \"%s\" appears to use leap seconds",
+								 *newval);
+				GUC_check_errdetail("PostgreSQL does not support leap seconds.");
+				return false;
+			}
+		}
+	}
+
+	/* Test for failure in pg_tzset_offset, which we assume is out-of-range */
+	if (!new_tz)
+	{
+		GUC_check_errdetail("UTC timezone offset is out of range.");
+		return false;
+	}
+
+	/*
+	 * Pass back data for assign_timezone to use
+	 */
+	*extra = malloc(sizeof(pg_tz *));
+	if (!*extra)
+		return false;
+	*((pg_tz **) *extra) = new_tz;
+
+	return true;
+}
+
+/*
+ * assign_timezone: GUC assign_hook for timezone
+ */
+void
+assign_timezone(const char *newval, void *extra)
+{
+	session_timezone = *((pg_tz **) extra);
+}
+
+/*
+ * show_timezone: GUC show_hook for timezone
+ */
+const char *
+show_timezone(void)
+{
+	const char *tzn;
+
+	/* Always show the zone's canonical name */
+	tzn = pg_get_timezone_name(session_timezone);
+
+	if (tzn != NULL)
+		return tzn;
+
+	return "unknown";
+}
+
+
+/*
+ * LOG_TIMEZONE
+ *
+ * For log_timezone, we don't support the interval-based methods of setting a
+ * zone, which are only there for SQL spec compliance not because they're
+ * actually useful.
+ */
+
+/*
+ * check_log_timezone: GUC check_hook for log_timezone
+ */
+bool
+check_log_timezone(char **newval, void **extra, GucSource source)
+{
+	pg_tz	   *new_tz;
+
+	/*
+	 * Assume it is a timezone name, and try to load it.
+	 */
+	new_tz = pg_tzset(*newval);
+
+	if (!new_tz)
+	{
+		/* Doesn't seem to be any great value in errdetail here */
+		return false;
+	}
+
+	if (!pg_tz_acceptable(new_tz))
+	{
+		GUC_check_errmsg("time zone \"%s\" appears to use leap seconds",
+						 *newval);
+		GUC_check_errdetail("PostgreSQL does not support leap seconds.");
+		return false;
+	}
+
+	/*
+	 * Pass back data for assign_log_timezone to use
+	 */
+	*extra = malloc(sizeof(pg_tz *));
+	if (!*extra)
+		return false;
+	*((pg_tz **) *extra) = new_tz;
+
+	return true;
+}
+
+/*
+ * assign_log_timezone: GUC assign_hook for log_timezone
+ */
+void
+assign_log_timezone(const char *newval, void *extra)
+{
+	log_timezone = *((pg_tz **) extra);
+}
+
+/*
+ * show_log_timezone: GUC show_hook for log_timezone
+ */
+const char *
+show_log_timezone(void)
+{
+	const char *tzn;
+
+	/* Always show the zone's canonical name */
+	tzn = pg_get_timezone_name(log_timezone);
+
+	if (tzn != NULL)
+		return tzn;
+
+	return "unknown";
+}
+
+
+/*
+ * SET TRANSACTION READ ONLY and SET TRANSACTION READ WRITE
+ *
+ * We allow idempotent changes (r/w -> r/w and r/o -> r/o) at any time, and
+ * we also always allow changes from read-write to read-only.  However,
+ * read-only may be changed to read-write only when in a top-level transaction
+ * that has not yet taken an initial snapshot.  Can't do it in a hot standby,
+ * either.
+ *
+ * If we are not in a transaction at all, just allow the change; it means
+ * nothing since XactReadOnly will be reset by the next StartTransaction().
+ * The IsTransactionState() test protects us against trying to check
+ * RecoveryInProgress() in contexts where shared memory is not accessible.
+ * (Similarly, if we're restoring state in a parallel worker, just allow
+ * the change.)
+ */
+bool
+check_transaction_read_only(bool *newval, void **extra, GucSource source)
+{
+	if (*newval == false && XactReadOnly && IsTransactionState() && !InitializingParallelWorker)
+	{
+		/* Can't go to r/w mode inside a r/o transaction */
+		if (IsSubTransaction())
+		{
+			GUC_check_errcode(ERRCODE_ACTIVE_SQL_TRANSACTION);
+			GUC_check_errmsg("cannot set transaction read-write mode inside a read-only transaction");
+			return false;
+		}
+		/* Top level transaction can't change to r/w after first snapshot. */
+		if (FirstSnapshotSet)
+		{
+			GUC_check_errcode(ERRCODE_ACTIVE_SQL_TRANSACTION);
+			GUC_check_errmsg("transaction read-write mode must be set before any query");
+			return false;
+		}
+		/* Can't go to r/w mode while recovery is still active */
+		if (RecoveryInProgress())
+		{
+			GUC_check_errcode(ERRCODE_FEATURE_NOT_SUPPORTED);
+			GUC_check_errmsg("cannot set transaction read-write mode during recovery");
+			return false;
+		}
+	}
+
+	return true;
+}
+
+/*
+ * SET TRANSACTION ISOLATION LEVEL
+ *
+ * We allow idempotent changes at any time, but otherwise this can only be
+ * changed in a toplevel transaction that has not yet taken a snapshot.
+ *
+ * As in check_transaction_read_only, allow it if not inside a transaction.
+ */
+bool
+check_XactIsoLevel(int *newval, void **extra, GucSource source)
+{
+	int			newXactIsoLevel = *newval;
+
+	if (newXactIsoLevel != XactIsoLevel && IsTransactionState())
+	{
+		if (FirstSnapshotSet)
+		{
+			GUC_check_errcode(ERRCODE_ACTIVE_SQL_TRANSACTION);
+			GUC_check_errmsg("SET TRANSACTION ISOLATION LEVEL must be called before any query");
+			return false;
+		}
+		/* We ignore a subtransaction setting it to the existing value. */
+		if (IsSubTransaction())
+		{
+			GUC_check_errcode(ERRCODE_ACTIVE_SQL_TRANSACTION);
+			GUC_check_errmsg("SET TRANSACTION ISOLATION LEVEL must not be called in a subtransaction");
+			return false;
+		}
+		/* Can't go to serializable mode while recovery is still active */
+		if (newXactIsoLevel == XACT_SERIALIZABLE && RecoveryInProgress())
+		{
+			GUC_check_errcode(ERRCODE_FEATURE_NOT_SUPPORTED);
+			GUC_check_errmsg("cannot use serializable mode in a hot standby");
+			GUC_check_errhint("You can use REPEATABLE READ instead.");
+			return false;
+		}
+	}
+
+	return true;
+}
+
+/*
+ * SET TRANSACTION [NOT] DEFERRABLE
+ */
+
+bool
+check_transaction_deferrable(bool *newval, void **extra, GucSource source)
+{
+	if (IsSubTransaction())
+	{
+		GUC_check_errcode(ERRCODE_ACTIVE_SQL_TRANSACTION);
+		GUC_check_errmsg("SET TRANSACTION [NOT] DEFERRABLE cannot be called within a subtransaction");
+		return false;
+	}
+	if (FirstSnapshotSet)
+	{
+		GUC_check_errcode(ERRCODE_ACTIVE_SQL_TRANSACTION);
+		GUC_check_errmsg("SET TRANSACTION [NOT] DEFERRABLE must be called before any query");
+		return false;
+	}
+
+	return true;
+}
+
+/*
+ * Random number seed
+ *
+ * We can't roll back the random sequence on error, and we don't want
+ * config file reloads to affect it, so we only want interactive SET SEED
+ * commands to set it.  We use the "extra" storage to ensure that rollbacks
+ * don't try to do the operation again.
+ */
+
+bool
+check_random_seed(double *newval, void **extra, GucSource source)
+{
+	*extra = malloc(sizeof(int));
+	if (!*extra)
+		return false;
+	/* Arm the assign only if source of value is an interactive SET */
+	*((int *) *extra) = (source >= PGC_S_INTERACTIVE);
+
+	return true;
+}
+
+void
+assign_random_seed(double newval, void *extra)
+{
+	/* We'll do this at most once for any setting of the GUC variable */
+	if (*((int *) extra))
+		DirectFunctionCall1(setseed, Float8GetDatum(newval));
+	*((int *) extra) = 0;
+}
+
+const char *
+show_random_seed(void)
+{
+	return "unavailable";
+}
+
+
+/*
+ * SET CLIENT_ENCODING
+ */
+
+bool
+check_client_encoding(char **newval, void **extra, GucSource source)
+{
+	int			encoding;
+	const char *canonical_name;
+
+	/* Look up the encoding by name */
+	encoding = pg_valid_client_encoding(*newval);
+	if (encoding < 0)
+		return false;
+
+	/* Get the canonical name (no aliases, uniform case) */
+	canonical_name = pg_encoding_to_char(encoding);
+
+	/*
+	 * If we are not within a transaction then PrepareClientEncoding will not
+	 * be able to look up the necessary conversion procs.  If we are still
+	 * starting up, it will return "OK" anyway, and InitializeClientEncoding
+	 * will fix things once initialization is far enough along.  After
+	 * startup, we'll fail.  This would only happen if someone tries to change
+	 * client_encoding in postgresql.conf and then SIGHUP existing sessions.
+	 * It seems like a bad idea for client_encoding to change that way anyhow,
+	 * so we don't go out of our way to support it.
+	 *
+	 * Note: in the postmaster, or any other process that never calls
+	 * InitializeClientEncoding, PrepareClientEncoding will always succeed,
+	 * and so will SetClientEncoding; but they won't do anything, which is OK.
+	 */
+	if (PrepareClientEncoding(encoding) < 0)
+	{
+		if (IsTransactionState())
+		{
+			/* Must be a genuine no-such-conversion problem */
+			GUC_check_errcode(ERRCODE_FEATURE_NOT_SUPPORTED);
+			GUC_check_errdetail("Conversion between %s and %s is not supported.",
+								canonical_name,
+								GetDatabaseEncodingName());
+		}
+		else
+		{
+			/* Provide a useful complaint */
+			GUC_check_errdetail("Cannot change \"client_encoding\" now.");
+		}
+		return false;
+	}
+
+	/*
+	 * Replace the user-supplied string with the encoding's canonical name.
+	 * This gets rid of aliases and case-folding variations.
+	 *
+	 * XXX Although canonicalizing seems like a good idea in the abstract, it
+	 * breaks pre-9.1 JDBC drivers, which expect that if they send "UNICODE"
+	 * as the client_encoding setting then it will read back the same way. As
+	 * a workaround, don't replace the string if it's "UNICODE".  Remove that
+	 * hack when pre-9.1 JDBC drivers are no longer in use.
+	 */
+	if (strcmp(*newval, canonical_name) != 0 &&
+		strcmp(*newval, "UNICODE") != 0)
+	{
+		free(*newval);
+		*newval = strdup(canonical_name);
+		if (!*newval)
+			return false;
+	}
+
+	/*
+	 * Save the encoding's ID in *extra, for use by assign_client_encoding.
+	 */
+	*extra = malloc(sizeof(int));
+	if (!*extra)
+		return false;
+	*((int *) *extra) = encoding;
+
+	return true;
+}
+
+void
+assign_client_encoding(const char *newval, void *extra)
+{
+	int			encoding = *((int *) extra);
+
+	/*
+	 * Parallel workers send data to the leader, not the client.  They always
+	 * send data using the database encoding.
+	 */
+	if (IsParallelWorker())
+	{
+		/*
+		 * During parallel worker startup, we want to accept the leader's
+		 * client_encoding setting so that anyone who looks at the value in
+		 * the worker sees the same value that they would see in the leader.
+		 */
+		if (InitializingParallelWorker)
+			return;
+
+		/*
+		 * A change other than during startup, for example due to a SET clause
+		 * attached to a function definition, should be rejected, as there is
+		 * nothing we can do inside the worker to make it take effect.
+		 */
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
+				 errmsg("cannot change client_encoding during a parallel operation")));
+	}
+
+	/* We do not expect an error if PrepareClientEncoding succeeded */
+	if (SetClientEncoding(encoding) < 0)
+		elog(LOG, "SetClientEncoding(%d) failed", encoding);
+}
+
+
+/*
+ * SET SESSION AUTHORIZATION
+ */
+
+typedef struct
+{
+	/* This is the "extra" state for both SESSION AUTHORIZATION and ROLE */
+	Oid			roleid;
+	bool		is_superuser;
+} role_auth_extra;
+
+bool
+check_session_authorization(char **newval, void **extra, GucSource source)
+{
+	HeapTuple	roleTup;
+	Form_pg_authid roleform;
+	Oid			roleid;
+	bool		is_superuser;
+	role_auth_extra *myextra;
+
+	/* Do nothing for the boot_val default of NULL */
+	if (*newval == NULL)
+		return true;
+
+	if (!IsTransactionState())
+	{
+		/*
+		 * Can't do catalog lookups, so fail.  The result of this is that
+		 * session_authorization cannot be set in postgresql.conf, which seems
+		 * like a good thing anyway, so we don't work hard to avoid it.
+		 */
+		return false;
+	}
+
+	/* Look up the username */
+	roleTup = SearchSysCache1(AUTHNAME, PointerGetDatum(*newval));
+	if (!HeapTupleIsValid(roleTup))
+	{
+		/*
+		 * When source == PGC_S_TEST, we don't throw a hard error for a
+		 * nonexistent user name, only a NOTICE.  See comments in guc.h.
+		 */
+		if (source == PGC_S_TEST)
+		{
+			ereport(NOTICE,
+					(errcode(ERRCODE_UNDEFINED_OBJECT),
+					 errmsg("role \"%s\" does not exist", *newval)));
+			return true;
+		}
+		GUC_check_errmsg("role \"%s\" does not exist", *newval);
+		return false;
+	}
+
+	roleform = (Form_pg_authid) GETSTRUCT(roleTup);
+	roleid = roleform->oid;
+	is_superuser = roleform->rolsuper;
+
+	ReleaseSysCache(roleTup);
+
+	/* Set up "extra" struct for assign_session_authorization to use */
+	myextra = (role_auth_extra *) malloc(sizeof(role_auth_extra));
+	if (!myextra)
+		return false;
+	myextra->roleid = roleid;
+	myextra->is_superuser = is_superuser;
+	*extra = (void *) myextra;
+
+	return true;
+}
+
+void
+assign_session_authorization(const char *newval, void *extra)
+{
+	role_auth_extra *myextra = (role_auth_extra *) extra;
+
+	/* Do nothing for the boot_val default of NULL */
+	if (!myextra)
+		return;
+
+	SetSessionAuthorization(myextra->roleid, myextra->is_superuser);
+}
+
+
+/*
+ * SET ROLE
+ *
+ * The SQL spec requires "SET ROLE NONE" to unset the role, so we hardwire
+ * a translation of "none" to InvalidOid.  Otherwise this is much like
+ * SET SESSION AUTHORIZATION.
+ */
+extern char *role_string;		/* in guc.c */
+
+bool
+check_role(char **newval, void **extra, GucSource source)
+{
+	HeapTuple	roleTup;
+	Oid			roleid;
+	bool		is_superuser;
+	role_auth_extra *myextra;
+	Form_pg_authid roleform;
+
+	if (strcmp(*newval, "none") == 0)
+	{
+		/* hardwired translation */
+		roleid = InvalidOid;
+		is_superuser = false;
+	}
+	else
+	{
+		if (!IsTransactionState())
+		{
+			/*
+			 * Can't do catalog lookups, so fail.  The result of this is that
+			 * role cannot be set in postgresql.conf, which seems like a good
+			 * thing anyway, so we don't work hard to avoid it.
+			 */
+			return false;
+		}
+
+		/*
+		 * When source == PGC_S_TEST, we don't throw a hard error for a
+		 * nonexistent user name or insufficient privileges, only a NOTICE.
+		 * See comments in guc.h.
+		 */
+
+		/* Look up the username */
+		roleTup = SearchSysCache1(AUTHNAME, PointerGetDatum(*newval));
+		if (!HeapTupleIsValid(roleTup))
+		{
+			if (source == PGC_S_TEST)
+			{
+				ereport(NOTICE,
+						(errcode(ERRCODE_UNDEFINED_OBJECT),
+						 errmsg("role \"%s\" does not exist", *newval)));
+				return true;
+			}
+			GUC_check_errmsg("role \"%s\" does not exist", *newval);
+			return false;
+		}
+
+		roleform = (Form_pg_authid) GETSTRUCT(roleTup);
+		roleid = roleform->oid;
+		is_superuser = roleform->rolsuper;
+
+		ReleaseSysCache(roleTup);
+
+		/*
+		 * Verify that session user is allowed to become this role, but skip
+		 * this in parallel mode, where we must blindly recreate the parallel
+		 * leader's state.
+		 */
+		if (!InitializingParallelWorker &&
+			!is_member_of_role(GetSessionUserId(), roleid))
+		{
+			if (source == PGC_S_TEST)
+			{
+				ereport(NOTICE,
+						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+						 errmsg("permission will be denied to set role \"%s\"",
+								*newval)));
+				return true;
+			}
+			GUC_check_errcode(ERRCODE_INSUFFICIENT_PRIVILEGE);
+			GUC_check_errmsg("permission denied to set role \"%s\"",
+							 *newval);
+			return false;
+		}
+	}
+
+	/* Set up "extra" struct for assign_role to use */
+	myextra = (role_auth_extra *) malloc(sizeof(role_auth_extra));
+	if (!myextra)
+		return false;
+	myextra->roleid = roleid;
+	myextra->is_superuser = is_superuser;
+	*extra = (void *) myextra;
+
+	return true;
+}
+
+void
+assign_role(const char *newval, void *extra)
+{
+	role_auth_extra *myextra = (role_auth_extra *) extra;
+
+	SetCurrentRoleId(myextra->roleid, myextra->is_superuser);
+}
+
+const char *
+show_role(void)
+{
+	/*
+	 * Check whether SET ROLE is active; if not return "none".  This is a
+	 * kluge to deal with the fact that SET SESSION AUTHORIZATION logically
+	 * resets SET ROLE to NONE, but we cannot set the GUC role variable from
+	 * assign_session_authorization (because we haven't got enough info to
+	 * call set_config_option).
+	 */
+	if (!OidIsValid(GetCurrentRoleId()))
+		return "none";
+
+	/* Otherwise we can just use the GUC string */
+	return role_string ? role_string : "none";
+}