src/bin/pg_dump/dumputils.c

/*-------------------------------------------------------------------------
 *
 * Utility routines for SQL dumping
 *
 * Basically this is stuff that is useful in both pg_dump and pg_dumpall.
 *
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/bin/pg_dump/dumputils.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres_fe.h"

#include <ctype.h>

#include "dumputils.h"
#include "fe_utils/string_utils.h"


static bool parseAclItem(const char *item, const char *type,
						 const char *name, const char *subname, int remoteVersion,
						 PQExpBuffer grantee, PQExpBuffer grantor,
						 PQExpBuffer privs, PQExpBuffer privswgo);
static char *copyAclUserName(PQExpBuffer output, char *input);
static void AddAcl(PQExpBuffer aclbuf, const char *keyword,
				   const char *subname);


/*
 * Build GRANT/REVOKE command(s) for an object.
 *
 *	name: the object name, in the form to use in the commands (already quoted)
 *	subname: the sub-object name, if any (already quoted); NULL if none
 *	nspname: the namespace the object is in (NULL if none); not pre-quoted
 *	type: the object type (as seen in GRANT command: must be one of
 *		TABLE, SEQUENCE, FUNCTION, PROCEDURE, LANGUAGE, SCHEMA, DATABASE, TABLESPACE,
 *		FOREIGN DATA WRAPPER, SERVER, or LARGE OBJECT)
 *	acls: the ACL string fetched from the database
 *	racls: the ACL string of any initial-but-now-revoked privileges
 *	owner: username of object owner (will be passed through fmtId); can be
 *		NULL or empty string to indicate "no owner known"
 *	prefix: string to prefix to each generated command; typically empty
 *	remoteVersion: version of database
 *
 * Returns true if okay, false if could not parse the acl string.
 * The resulting commands (if any) are appended to the contents of 'sql'.
 *
 * Note: when processing a default ACL, prefix is "ALTER DEFAULT PRIVILEGES "
 * or something similar, and name is an empty string.
 *
 * Note: beware of passing a fmtId() result directly as 'name' or 'subname',
 * since this routine uses fmtId() internally.
 */
bool
buildACLCommands(const char *name, const char *subname, const char *nspname,
				 const char *type, const char *acls, const char *racls,
				 const char *owner, const char *prefix, int remoteVersion,
				 PQExpBuffer sql)
{
	bool		ok = true;
	char	  **aclitems = NULL;
	char	  **raclitems = NULL;
	int			naclitems = 0;
	int			nraclitems = 0;
	int			i;
	PQExpBuffer grantee,
				grantor,
				privs,
				privswgo;
	PQExpBuffer firstsql,
				secondsql;
	bool		found_owner_privs = false;

	if (strlen(acls) == 0 && strlen(racls) == 0)
		return true;			/* object has default permissions */

	/* treat empty-string owner same as NULL */
	if (owner && *owner == '\0')
		owner = NULL;

	if (strlen(acls) != 0)
	{
		if (!parsePGArray(acls, &aclitems, &naclitems))
		{
			if (aclitems)
				free(aclitems);
			return false;
		}
	}

	if (strlen(racls) != 0)
	{
		if (!parsePGArray(racls, &raclitems, &nraclitems))
		{
			if (aclitems)
				free(aclitems);
			if (raclitems)
				free(raclitems);
			return false;
		}
	}

	grantee = createPQExpBuffer();
	grantor = createPQExpBuffer();
	privs = createPQExpBuffer();
	privswgo = createPQExpBuffer();

	/*
	 * At the end, these two will be pasted together to form the result.
	 *
	 * For older systems we use these to ensure that the owner privileges go
	 * before the other ones, as a GRANT could create the default entry for
	 * the object, which generally includes all rights for the owner. In more
	 * recent versions we normally handle this because the owner rights come
	 * first in the ACLs, but older versions might have them after the PUBLIC
	 * privileges.
	 *
	 * For 9.6 and later systems, much of this changes.  With 9.6, we check
	 * the default privileges for the objects at dump time and create two sets
	 * of ACLs- "racls" which are the ACLs to REVOKE from the object (as the
	 * object may have initial privileges on it, along with any default ACLs
	 * which are not part of the current set of privileges), and regular
	 * "acls", which are the ACLs to GRANT to the object.  We handle the
	 * REVOKEs first, followed by the GRANTs.
	 */
	firstsql = createPQExpBuffer();
	secondsql = createPQExpBuffer();

	/*
	 * For pre-9.6 systems, we always start with REVOKE ALL FROM PUBLIC, as we
	 * don't wish to make any assumptions about what the default ACLs are, and
	 * we do not collect them during the dump phase (and racls will always be
	 * the empty set, see above).
	 *
	 * For 9.6 and later, if any revoke ACLs have been provided, then include
	 * them in 'firstsql'.
	 *
	 * Revoke ACLs happen when an object starts out life with a set of
	 * privileges (eg: GRANT SELECT ON pg_class TO PUBLIC;) and the user has
	 * decided to revoke those rights.  Since those objects come into being
	 * with those default privileges, we have to revoke them to match what the
	 * current state of affairs is.  Note that we only started explicitly
	 * tracking such initial rights in 9.6, and prior to that all initial
	 * rights are actually handled by the simple 'REVOKE ALL .. FROM PUBLIC'
	 * case, for initdb-created objects.  Prior to 9.6, we didn't handle
	 * extensions correctly, but we do now by tracking their initial
	 * privileges, in the same way we track initdb initial privileges, see
	 * pg_init_privs.
	 */
	if (remoteVersion < 90600)
	{
		Assert(nraclitems == 0);

		appendPQExpBuffer(firstsql, "%sREVOKE ALL", prefix);
		if (subname)
			appendPQExpBuffer(firstsql, "(%s)", subname);
		appendPQExpBuffer(firstsql, " ON %s ", type);
		if (nspname && *nspname)
			appendPQExpBuffer(firstsql, "%s.", fmtId(nspname));
		appendPQExpBuffer(firstsql, "%s FROM PUBLIC;\n", name);
	}
	else
	{
		/* Scan individual REVOKE ACL items */
		for (i = 0; i < nraclitems; i++)
		{
			if (!parseAclItem(raclitems[i], type, name, subname, remoteVersion,
							  grantee, grantor, privs, NULL))
			{
				ok = false;
				break;
			}

			if (privs->len > 0)
			{
				appendPQExpBuffer(firstsql, "%sREVOKE %s ON %s ",
								  prefix, privs->data, type);
				if (nspname && *nspname)
					appendPQExpBuffer(firstsql, "%s.", fmtId(nspname));
				appendPQExpBuffer(firstsql, "%s FROM ", name);
				if (grantee->len == 0)
					appendPQExpBufferStr(firstsql, "PUBLIC;\n");
				else if (strncmp(grantee->data, "group ",
								 strlen("group ")) == 0)
					appendPQExpBuffer(firstsql, "GROUP %s;\n",
									  fmtId(grantee->data + strlen("group ")));
				else
					appendPQExpBuffer(firstsql, "%s;\n",
									  fmtId(grantee->data));
			}
		}
	}

	/* Scan individual ACL items */
	for (i = 0; i < naclitems; i++)
	{
		if (!parseAclItem(aclitems[i], type, name, subname, remoteVersion,
						  grantee, grantor, privs, privswgo))
		{
			ok = false;
			break;
		}

		if (grantor->len == 0 && owner)
			printfPQExpBuffer(grantor, "%s", owner);

		if (privs->len > 0 || privswgo->len > 0)
		{
			/*
			 * Prior to 9.6, we had to handle owner privileges in a special
			 * manner by first REVOKE'ing the rights and then GRANT'ing them
			 * after.  With 9.6 and above, what we need to REVOKE and what we
			 * need to GRANT is figured out when we dump and stashed into
			 * "racls" and "acls", respectively.  See above.
			 */
			if (remoteVersion < 90600 && owner
				&& strcmp(grantee->data, owner) == 0
				&& strcmp(grantor->data, owner) == 0)
			{
				found_owner_privs = true;

				/*
				 * For the owner, the default privilege level is ALL WITH
				 * GRANT OPTION.
				 */
				if (strcmp(privswgo->data, "ALL") != 0)
				{
					appendPQExpBuffer(firstsql, "%sREVOKE ALL", prefix);
					if (subname)
						appendPQExpBuffer(firstsql, "(%s)", subname);
					appendPQExpBuffer(firstsql, " ON %s ", type);
					if (nspname && *nspname)
						appendPQExpBuffer(firstsql, "%s.", fmtId(nspname));
					appendPQExpBuffer(firstsql, "%s FROM %s;\n",
									  name, fmtId(grantee->data));
					if (privs->len > 0)
					{
						appendPQExpBuffer(firstsql,
										  "%sGRANT %s ON %s ",
										  prefix, privs->data, type);
						if (nspname && *nspname)
							appendPQExpBuffer(firstsql, "%s.", fmtId(nspname));
						appendPQExpBuffer(firstsql,
										  "%s TO %s;\n",
										  name, fmtId(grantee->data));
					}
					if (privswgo->len > 0)
					{
						appendPQExpBuffer(firstsql,
										  "%sGRANT %s ON %s ",
										  prefix, privswgo->data, type);
						if (nspname && *nspname)
							appendPQExpBuffer(firstsql, "%s.", fmtId(nspname));
						appendPQExpBuffer(firstsql,
										  "%s TO %s WITH GRANT OPTION;\n",
										  name, fmtId(grantee->data));
					}
				}
			}
			else
			{
				/*
				 * For systems prior to 9.6, we can assume we are starting
				 * from no privs at this point.
				 *
				 * For 9.6 and above, at this point we have issued REVOKE
				 * statements for all initial and default privileges which are
				 * no longer present on the object (as they were passed in as
				 * 'racls') and we can simply GRANT the rights which are in
				 * 'acls'.
				 */
				if (grantor->len > 0
					&& (!owner || strcmp(owner, grantor->data) != 0))
					appendPQExpBuffer(secondsql, "SET SESSION AUTHORIZATION %s;\n",
									  fmtId(grantor->data));

				if (privs->len > 0)
				{
					appendPQExpBuffer(secondsql, "%sGRANT %s ON %s ",
									  prefix, privs->data, type);
					if (nspname && *nspname)
						appendPQExpBuffer(secondsql, "%s.", fmtId(nspname));
					appendPQExpBuffer(secondsql, "%s TO ", name);
					if (grantee->len == 0)
						appendPQExpBufferStr(secondsql, "PUBLIC;\n");
					else if (strncmp(grantee->data, "group ",
									 strlen("group ")) == 0)
						appendPQExpBuffer(secondsql, "GROUP %s;\n",
										  fmtId(grantee->data + strlen("group ")));
					else
						appendPQExpBuffer(secondsql, "%s;\n", fmtId(grantee->data));
				}
				if (privswgo->len > 0)
				{
					appendPQExpBuffer(secondsql, "%sGRANT %s ON %s ",
									  prefix, privswgo->data, type);
					if (nspname && *nspname)
						appendPQExpBuffer(secondsql, "%s.", fmtId(nspname));
					appendPQExpBuffer(secondsql, "%s TO ", name);
					if (grantee->len == 0)
						appendPQExpBufferStr(secondsql, "PUBLIC");
					else if (strncmp(grantee->data, "group ",
									 strlen("group ")) == 0)
						appendPQExpBuffer(secondsql, "GROUP %s",
										  fmtId(grantee->data + strlen("group ")));
					else
						appendPQExpBufferStr(secondsql, fmtId(grantee->data));
					appendPQExpBufferStr(secondsql, " WITH GRANT OPTION;\n");
				}

				if (grantor->len > 0
					&& (!owner || strcmp(owner, grantor->data) != 0))
					appendPQExpBufferStr(secondsql, "RESET SESSION AUTHORIZATION;\n");
			}
		}
	}

	/*
	 * For systems prior to 9.6, if we didn't find any owner privs, the owner
	 * must have revoked 'em all.
	 *
	 * For 9.6 and above, we handle this through the 'racls'.  See above.
	 */
	if (remoteVersion < 90600 && !found_owner_privs && owner)
	{
		appendPQExpBuffer(firstsql, "%sREVOKE ALL", prefix);
		if (subname)
			appendPQExpBuffer(firstsql, "(%s)", subname);
		appendPQExpBuffer(firstsql, " ON %s ", type);
		if (nspname && *nspname)
			appendPQExpBuffer(firstsql, "%s.", fmtId(nspname));
		appendPQExpBuffer(firstsql, "%s FROM %s;\n",
						  name, fmtId(owner));
	}

	destroyPQExpBuffer(grantee);
	destroyPQExpBuffer(grantor);
	destroyPQExpBuffer(privs);
	destroyPQExpBuffer(privswgo);

	appendPQExpBuffer(sql, "%s%s", firstsql->data, secondsql->data);
	destroyPQExpBuffer(firstsql);
	destroyPQExpBuffer(secondsql);

	if (aclitems)
		free(aclitems);

	if (raclitems)
		free(raclitems);

	return ok;
}

/*
 * Build ALTER DEFAULT PRIVILEGES command(s) for single pg_default_acl entry.
 *
 *	type: the object type (TABLES, FUNCTIONS, etc)
 *	nspname: schema name, or NULL for global default privileges
 *	acls: the ACL string fetched from the database
 *	owner: username of privileges owner (will be passed through fmtId)
 *	remoteVersion: version of database
 *
 * Returns true if okay, false if could not parse the acl string.
 * The resulting commands (if any) are appended to the contents of 'sql'.
 */
bool
buildDefaultACLCommands(const char *type, const char *nspname,
						const char *acls, const char *racls,
						const char *initacls, const char *initracls,
						const char *owner,
						int remoteVersion,
						PQExpBuffer sql)
{
	PQExpBuffer prefix;

	prefix = createPQExpBuffer();

	/*
	 * We incorporate the target role directly into the command, rather than
	 * playing around with SET ROLE or anything like that.  This is so that a
	 * permissions error leads to nothing happening, rather than changing
	 * default privileges for the wrong user.
	 */
	appendPQExpBuffer(prefix, "ALTER DEFAULT PRIVILEGES FOR ROLE %s ",
					  fmtId(owner));
	if (nspname)
		appendPQExpBuffer(prefix, "IN SCHEMA %s ", fmtId(nspname));

	if (strlen(initacls) != 0 || strlen(initracls) != 0)
	{
		appendPQExpBufferStr(sql, "SELECT pg_catalog.binary_upgrade_set_record_init_privs(true);\n");
		if (!buildACLCommands("", NULL, NULL, type,
							  initacls, initracls, owner,
							  prefix->data, remoteVersion, sql))
		{
			destroyPQExpBuffer(prefix);
			return false;
		}
		appendPQExpBufferStr(sql, "SELECT pg_catalog.binary_upgrade_set_record_init_privs(false);\n");
	}

	if (!buildACLCommands("", NULL, NULL, type,
						  acls, racls, owner,
						  prefix->data, remoteVersion, sql))
	{
		destroyPQExpBuffer(prefix);
		return false;
	}

	destroyPQExpBuffer(prefix);

	return true;
}

/*
 * This will parse an aclitem string, having the general form
 *		username=privilegecodes/grantor
 * or
 *		group groupname=privilegecodes/grantor
 * (the "group" case occurs only with servers before 8.1).
 *
 * Returns true on success, false on parse error.  On success, the components
 * of the string are returned in the PQExpBuffer parameters.
 *
 * The returned grantee string will be the dequoted username or groupname
 * (preceded with "group " in the latter case).  Note that a grant to PUBLIC
 * is represented by an empty grantee string.  The returned grantor is the
 * dequoted grantor name.  Privilege characters are translated to GRANT/REVOKE
 * comma-separated privileges lists.  If "privswgo" is non-NULL, the result is
 * separate lists for privileges with grant option ("privswgo") and without
 * ("privs").  Otherwise, "privs" bears every relevant privilege, ignoring the
 * grant option distinction.
 *
 * Note: for cross-version compatibility, it's important to use ALL to
 * represent the privilege sets whenever appropriate.
 */
static bool
parseAclItem(const char *item, const char *type,
			 const char *name, const char *subname, int remoteVersion,
			 PQExpBuffer grantee, PQExpBuffer grantor,
			 PQExpBuffer privs, PQExpBuffer privswgo)
{
	char	   *buf;
	bool		all_with_go = true;
	bool		all_without_go = true;
	char	   *eqpos;
	char	   *slpos;
	char	   *pos;

	buf = pg_strdup(item);

	/* user or group name is string up to = */
	eqpos = copyAclUserName(grantee, buf);
	if (*eqpos != '=')
	{
		pg_free(buf);
		return false;
	}

	/* grantor should appear after / */
	slpos = strchr(eqpos + 1, '/');
	if (slpos)
	{
		*slpos++ = '\0';
		slpos = copyAclUserName(grantor, slpos);
		if (*slpos != '\0')
		{
			pg_free(buf);
			return false;
		}
	}
	else
	{
		pg_free(buf);
		return false;
	}

	/* privilege codes */
#define CONVERT_PRIV(code, keywd) \
do { \
	if ((pos = strchr(eqpos + 1, code))) \
	{ \
		if (*(pos + 1) == '*' && privswgo != NULL) \
		{ \
			AddAcl(privswgo, keywd, subname); \
			all_without_go = false; \
		} \
		else \
		{ \
			AddAcl(privs, keywd, subname); \
			all_with_go = false; \
		} \
	} \
	else \
		all_with_go = all_without_go = false; \
} while (0)

	resetPQExpBuffer(privs);
	resetPQExpBuffer(privswgo);

	if (strcmp(type, "TABLE") == 0 || strcmp(type, "SEQUENCE") == 0 ||
		strcmp(type, "TABLES") == 0 || strcmp(type, "SEQUENCES") == 0)
	{
		CONVERT_PRIV('r', "SELECT");

		if (strcmp(type, "SEQUENCE") == 0 ||
			strcmp(type, "SEQUENCES") == 0)
			/* sequence only */
			CONVERT_PRIV('U', "USAGE");
		else
		{
			/* table only */
			CONVERT_PRIV('a', "INSERT");
			CONVERT_PRIV('x', "REFERENCES");
			/* rest are not applicable to columns */
			if (subname == NULL)
			{
				CONVERT_PRIV('d', "DELETE");
				CONVERT_PRIV('t', "TRIGGER");
				if (remoteVersion >= 80400)
					CONVERT_PRIV('D', "TRUNCATE");
			}
		}

		/* UPDATE */
		CONVERT_PRIV('w', "UPDATE");
	}
	else if (strcmp(type, "FUNCTION") == 0 ||
			 strcmp(type, "FUNCTIONS") == 0)
		CONVERT_PRIV('X', "EXECUTE");
	else if (strcmp(type, "PROCEDURE") == 0 ||
			 strcmp(type, "PROCEDURES") == 0)
		CONVERT_PRIV('X', "EXECUTE");
	else if (strcmp(type, "LANGUAGE") == 0)
		CONVERT_PRIV('U', "USAGE");
	else if (strcmp(type, "SCHEMA") == 0 ||
			 strcmp(type, "SCHEMAS") == 0)
	{
		CONVERT_PRIV('C', "CREATE");
		CONVERT_PRIV('U', "USAGE");
	}
	else if (strcmp(type, "DATABASE") == 0)
	{
		CONVERT_PRIV('C', "CREATE");
		CONVERT_PRIV('c', "CONNECT");
		CONVERT_PRIV('T', "TEMPORARY");
	}
	else if (strcmp(type, "TABLESPACE") == 0)
		CONVERT_PRIV('C', "CREATE");
	else if (strcmp(type, "TYPE") == 0 ||
			 strcmp(type, "TYPES") == 0)
		CONVERT_PRIV('U', "USAGE");
	else if (strcmp(type, "FOREIGN DATA WRAPPER") == 0)
		CONVERT_PRIV('U', "USAGE");
	else if (strcmp(type, "FOREIGN SERVER") == 0)
		CONVERT_PRIV('U', "USAGE");
	else if (strcmp(type, "FOREIGN TABLE") == 0)
		CONVERT_PRIV('r', "SELECT");
	else if (strcmp(type, "LARGE OBJECT") == 0)
	{
		CONVERT_PRIV('r', "SELECT");
		CONVERT_PRIV('w', "UPDATE");
	}
	else if (strcmp(type, "PROTOCOL") == 0)
	{
		CONVERT_PRIV('r', "SELECT");
		CONVERT_PRIV('a', "INSERT");
	}
	else
		abort();

#undef CONVERT_PRIV

	if (all_with_go)
	{
		resetPQExpBuffer(privs);
		printfPQExpBuffer(privswgo, "ALL");
		if (subname)
			appendPQExpBuffer(privswgo, "(%s)", subname);
	}
	else if (all_without_go)
	{
		resetPQExpBuffer(privswgo);
		printfPQExpBuffer(privs, "ALL");
		if (subname)
			appendPQExpBuffer(privs, "(%s)", subname);
	}

	pg_free(buf);

	return true;
}

/*
 * Transfer a user or group name starting at *input into the output buffer,
 * dequoting if needed.  Returns a pointer to just past the input name.
 * The name is taken to end at an unquoted '=' or end of string.
 */
static char *
copyAclUserName(PQExpBuffer output, char *input)
{
	resetPQExpBuffer(output);

	while (*input && *input != '=')
	{
		/*
		 * If user name isn't quoted, then just add it to the output buffer
		 */
		if (*input != '"')
			appendPQExpBufferChar(output, *input++);
		else
		{
			/* Otherwise, it's a quoted username */
			input++;
			/* Loop until we come across an unescaped quote */
			while (!(*input == '"' && *(input + 1) != '"'))
			{
				if (*input == '\0')
					return input;	/* really a syntax error... */

				/*
				 * Quoting convention is to escape " as "".  Keep this code in
				 * sync with putid() in backend's acl.c.
				 */
				if (*input == '"' && *(input + 1) == '"')
					input++;
				appendPQExpBufferChar(output, *input++);
			}
			input++;
		}
	}
	return input;
}

/*
 * Append a privilege keyword to a keyword list, inserting comma if needed.
 */
static void
AddAcl(PQExpBuffer aclbuf, const char *keyword, const char *subname)
{
	if (aclbuf->len > 0)
		appendPQExpBufferChar(aclbuf, ',');
	appendPQExpBufferStr(aclbuf, keyword);
	if (subname)
		appendPQExpBuffer(aclbuf, "(%s)", subname);
}


/*
 * buildShSecLabelQuery
 *
 * Build a query to retrieve security labels for a shared object.
 * The object is identified by its OID plus the name of the catalog
 * it can be found in (e.g., "pg_database" for database names).
 * The query is appended to "sql".  (We don't execute it here so as to
 * keep this file free of assumptions about how to deal with SQL errors.)
 */
void
buildShSecLabelQuery(const char *catalog_name, Oid objectId,
					 PQExpBuffer sql)
{
	appendPQExpBuffer(sql,
					  "SELECT provider, label FROM pg_catalog.pg_shseclabel "
					  "WHERE classoid = 'pg_catalog.%s'::pg_catalog.regclass "
					  "AND objoid = '%u'", catalog_name, objectId);
}

/*
 * emitShSecLabels
 *
 * Construct SECURITY LABEL commands using the data retrieved by the query
 * generated by buildShSecLabelQuery, and append them to "buffer".
 * Here, the target object is identified by its type name (e.g. "DATABASE")
 * and its name (not pre-quoted).
 */
void
emitShSecLabels(PGconn *conn, PGresult *res, PQExpBuffer buffer,
				const char *objtype, const char *objname)
{
	int			i;

	for (i = 0; i < PQntuples(res); i++)
	{
		char	   *provider = PQgetvalue(res, i, 0);
		char	   *label = PQgetvalue(res, i, 1);

		/* must use fmtId result before calling it again */
		appendPQExpBuffer(buffer,
						  "SECURITY LABEL FOR %s ON %s",
						  fmtId(provider), objtype);
		appendPQExpBuffer(buffer,
						  " %s IS ",
						  fmtId(objname));
		appendStringLiteralConn(buffer, label, conn);
		appendPQExpBufferStr(buffer, ";\n");
	}
}

/*
 * buildACLQueries
 *
 * Build the subqueries to extract out the correct set of ACLs to be
 * GRANT'd and REVOKE'd for the specific kind of object, accounting for any
 * initial privileges (from pg_init_privs) and based on if we are in binary
 * upgrade mode or not.
 *
 * Also builds subqueries to extract out the set of ACLs to go from the object
 * default privileges to the privileges in pg_init_privs, if we are in binary
 * upgrade mode, so that those privileges can be set up and recorded in the new
 * cluster before the regular privileges are added on top of those.
 */
void
buildACLQueries(PQExpBuffer acl_subquery, PQExpBuffer racl_subquery,
				PQExpBuffer init_acl_subquery, PQExpBuffer init_racl_subquery,
				const char *acl_column, const char *acl_owner,
				const char *obj_kind, bool binary_upgrade)
{
	/*
	 * To get the delta from what the permissions were at creation time
	 * (either initdb or CREATE EXTENSION) vs. what they are now, we have to
	 * look at two things:
	 *
	 * What privileges have been added, which we calculate by extracting all
	 * the current privileges (using the set of default privileges for the
	 * object type if current privileges are NULL) and then removing those
	 * which existed at creation time (again, using the set of default
	 * privileges for the object type if there were no creation time
	 * privileges).
	 *
	 * What privileges have been removed, which we calculate by extracting the
	 * privileges as they were at creation time (or the default privileges, as
	 * above), and then removing the current privileges (or the default
	 * privileges, if current privileges are NULL).
	 *
	 * As a good cross-check, both directions of these checks should result in
	 * the empty set if both the current ACL and the initial privs are NULL
	 * (meaning, in practice, that the default ACLs were there at init time
	 * and is what the current privileges are).
	 *
	 * We always perform this delta on all ACLs and expect that by the time
	 * these are run the initial privileges will be in place, even in a binary
	 * upgrade situation (see below).
	 *
	 * Finally, the order in which privileges are in the ACL string (the order
	 * they been GRANT'd in, which the backend maintains) must be preserved to
	 * ensure that GRANTs WITH GRANT OPTION and subsequent GRANTs based on
	 * those are dumped in the correct order.
	 */
	printfPQExpBuffer(acl_subquery,
					  "(SELECT pg_catalog.array_agg(acl ORDER BY row_n) FROM "
					  "(SELECT acl, row_n FROM "
					  "pg_catalog.unnest(coalesce(%s,pg_catalog.acldefault(%s,%s))) "
					  "WITH ORDINALITY AS perm(acl,row_n) "
					  "WHERE NOT EXISTS ( "
					  "SELECT 1 FROM "
					  "pg_catalog.unnest(coalesce(pip.initprivs,pg_catalog.acldefault(%s,%s))) "
					  "AS init(init_acl) WHERE acl = init_acl)) as foo)",
					  acl_column,
					  obj_kind,
					  acl_owner,
					  obj_kind,
					  acl_owner);

	printfPQExpBuffer(racl_subquery,
					  "(SELECT pg_catalog.array_agg(acl ORDER BY row_n) FROM "
					  "(SELECT acl, row_n FROM "
					  "pg_catalog.unnest(coalesce(pip.initprivs,pg_catalog.acldefault(%s,%s))) "
					  "WITH ORDINALITY AS initp(acl,row_n) "
					  "WHERE NOT EXISTS ( "
					  "SELECT 1 FROM "
					  "pg_catalog.unnest(coalesce(%s,pg_catalog.acldefault(%s,%s))) "
					  "AS permp(orig_acl) WHERE acl = orig_acl)) as foo)",
					  obj_kind,
					  acl_owner,
					  acl_column,
					  obj_kind,
					  acl_owner);

	/*
	 * In binary upgrade mode we don't run the extension script but instead
	 * dump out the objects independently and then recreate them.  To preserve
	 * the initial privileges which were set on extension objects, we need to
	 * grab the set of GRANT and REVOKE commands necessary to get from the
	 * default privileges of an object to the initial privileges as recorded
	 * in pg_init_privs.
	 *
	 * These will then be run ahead of the regular ACL commands, which were
	 * calculated using the queries above, inside of a block which sets a flag
	 * to indicate that the backend should record the results of these GRANT
	 * and REVOKE statements into pg_init_privs.  This is how we preserve the
	 * contents of that catalog across binary upgrades.
	 */
	if (binary_upgrade)
	{
		printfPQExpBuffer(init_acl_subquery,
						  "CASE WHEN privtype = 'e' THEN "
						  "(SELECT pg_catalog.array_agg(acl ORDER BY row_n) FROM "
						  "(SELECT acl, row_n FROM pg_catalog.unnest(pip.initprivs) "
						  "WITH ORDINALITY AS initp(acl,row_n) "
						  "WHERE NOT EXISTS ( "
						  "SELECT 1 FROM "
						  "pg_catalog.unnest(pg_catalog.acldefault(%s,%s)) "
						  "AS privm(orig_acl) WHERE acl = orig_acl)) as foo) END",
						  obj_kind,
						  acl_owner);

		printfPQExpBuffer(init_racl_subquery,
						  "CASE WHEN privtype = 'e' THEN "
						  "(SELECT pg_catalog.array_agg(acl) FROM "
						  "(SELECT acl, row_n FROM "
						  "pg_catalog.unnest(pg_catalog.acldefault(%s,%s)) "
						  "WITH ORDINALITY AS privp(acl,row_n) "
						  "WHERE NOT EXISTS ( "
						  "SELECT 1 FROM pg_catalog.unnest(pip.initprivs) "
						  "AS initp(init_acl) WHERE acl = init_acl)) as foo) END",
						  obj_kind,
						  acl_owner);
	}
	else
	{
		printfPQExpBuffer(init_acl_subquery, "NULL");
		printfPQExpBuffer(init_racl_subquery, "NULL");
	}
}

/*
 * Detect whether the given GUC variable is of GUC_LIST_QUOTE type.
 *
 * It'd be better if we could inquire this directly from the backend; but even
 * if there were a function for that, it could only tell us about variables
 * currently known to guc.c, so that it'd be unsafe for extensions to declare
 * GUC_LIST_QUOTE variables anyway.  Lacking a solution for that, it doesn't
 * seem worth the work to do more than have this list, which must be kept in
 * sync with the variables actually marked GUC_LIST_QUOTE in guc.c.
 */
bool
variable_is_guc_list_quote(const char *name)
{
	if (pg_strcasecmp(name, "local_preload_libraries") == 0 ||
		pg_strcasecmp(name, "search_path") == 0 ||
		pg_strcasecmp(name, "session_preload_libraries") == 0 ||
		pg_strcasecmp(name, "shared_preload_libraries") == 0 ||
		pg_strcasecmp(name, "temp_tablespaces") == 0 ||
		pg_strcasecmp(name, "unix_socket_directories") == 0)
		return true;
	else
		return false;
}

/*
 * SplitGUCList --- parse a string containing identifiers or file names
 *
 * This is used to split the value of a GUC_LIST_QUOTE GUC variable, without
 * presuming whether the elements will be taken as identifiers or file names.
 * See comparable code in src/backend/utils/adt/varlena.c.
 *
 * Inputs:
 *	rawstring: the input string; must be overwritable!	On return, it's
 *			   been modified to contain the separated identifiers.
 *	separator: the separator punctuation expected between identifiers
 *			   (typically '.' or ',').  Whitespace may also appear around
 *			   identifiers.
 * Outputs:
 *	namelist: receives a malloc'd, null-terminated array of pointers to
 *			  identifiers within rawstring.  Caller should free this
 *			  even on error return.
 *
 * Returns true if okay, false if there is a syntax error in the string.
 */
bool
SplitGUCList(char *rawstring, char separator,
			 char ***namelist)
{
	char	   *nextp = rawstring;
	bool		done = false;
	char	  **nextptr;

	/*
	 * Since we disallow empty identifiers, this is a conservative
	 * overestimate of the number of pointers we could need.  Allow one for
	 * list terminator.
	 */
	*namelist = nextptr = (char **)
		pg_malloc((strlen(rawstring) / 2 + 2) * sizeof(char *));
	*nextptr = NULL;

	while (isspace((unsigned char) *nextp))
		nextp++;				/* skip leading whitespace */

	if (*nextp == '\0')
		return true;			/* allow empty string */

	/* At the top of the loop, we are at start of a new identifier. */
	do
	{
		char	   *curname;
		char	   *endp;

		if (*nextp == '"')
		{
			/* Quoted name --- collapse quote-quote pairs */
			curname = nextp + 1;
			for (;;)
			{
				endp = strchr(nextp + 1, '"');
				if (endp == NULL)
					return false;	/* mismatched quotes */
				if (endp[1] != '"')
					break;		/* found end of quoted name */
				/* Collapse adjacent quotes into one quote, and look again */
				memmove(endp, endp + 1, strlen(endp));
				nextp = endp;
			}
			/* endp now points at the terminating quote */
			nextp = endp + 1;
		}
		else
		{
			/* Unquoted name --- extends to separator or whitespace */
			curname = nextp;
			while (*nextp && *nextp != separator &&
				   !isspace((unsigned char) *nextp))
				nextp++;
			endp = nextp;
			if (curname == nextp)
				return false;	/* empty unquoted name not allowed */
		}

		while (isspace((unsigned char) *nextp))
			nextp++;			/* skip trailing whitespace */

		if (*nextp == separator)
		{
			nextp++;
			while (isspace((unsigned char) *nextp))
				nextp++;		/* skip leading whitespace for next */
			/* we expect another name, so done remains false */
		}
		else if (*nextp == '\0')
			done = true;
		else
			return false;		/* invalid syntax */

		/* Now safe to overwrite separator with a null */
		*endp = '\0';

		/*
		 * Finished isolating current name --- add it to output array
		 */
		*nextptr++ = curname;

		/* Loop back if we didn't reach end of string */
	} while (!done);

	*nextptr = NULL;
	return true;
}

/*
 * Helper function for dumping "ALTER DATABASE/ROLE SET ..." commands.
 *
 * Parse the contents of configitem (a "name=value" string), wrap it in
 * a complete ALTER command, and append it to buf.
 *
 * type is DATABASE or ROLE, and name is the name of the database or role.
 * If we need an "IN" clause, type2 and name2 similarly define what to put
 * there; otherwise they should be NULL.
 * conn is used only to determine string-literal quoting conventions.
 */
void
makeAlterConfigCommand(PGconn *conn, const char *configitem,
					   const char *type, const char *name,
					   const char *type2, const char *name2,
					   PQExpBuffer buf)
{
	char	   *mine;
	char	   *pos;

	/* Parse the configitem.  If we can't find an "=", silently do nothing. */
	mine = pg_strdup(configitem);
	pos = strchr(mine, '=');
	if (pos == NULL)
	{
		pg_free(mine);
		return;
	}
	*pos++ = '\0';

	/* Build the command, with suitable quoting for everything. */
	appendPQExpBuffer(buf, "ALTER %s %s ", type, fmtId(name));
	if (type2 != NULL && name2 != NULL)
		appendPQExpBuffer(buf, "IN %s %s ", type2, fmtId(name2));
	appendPQExpBuffer(buf, "SET %s TO ", fmtId(mine));

	/*
	 * Variables that are marked GUC_LIST_QUOTE were already fully quoted by
	 * flatten_set_variable_args() before they were put into the setconfig
	 * array.  However, because the quoting rules used there aren't exactly
	 * like SQL's, we have to break the list value apart and then quote the
	 * elements as string literals.  (The elements may be double-quoted as-is,
	 * but we can't just feed them to the SQL parser; it would do the wrong
	 * thing with elements that are zero-length or longer than NAMEDATALEN.)
	 *
	 * Variables that are not so marked should just be emitted as simple
	 * string literals.  If the variable is not known to
	 * variable_is_guc_list_quote(), we'll do that; this makes it unsafe to
	 * use GUC_LIST_QUOTE for extension variables.
	 */
	if (variable_is_guc_list_quote(mine))
	{
		char	  **namelist;
		char	  **nameptr;

		/* Parse string into list of identifiers */
		/* this shouldn't fail really */
		if (SplitGUCList(pos, ',', &namelist))
		{
			for (nameptr = namelist; *nameptr; nameptr++)
			{
				if (nameptr != namelist)
					appendPQExpBufferStr(buf, ", ");
				appendStringLiteralConn(buf, *nameptr, conn);
			}
		}
		pg_free(namelist);
	}
	else
		appendStringLiteralConn(buf, pos, conn);

	appendPQExpBufferStr(buf, ";\n");

	pg_free(mine);
}