src/backend/catalog/pg_db_role_setting.c - cloudberry - Git at Google

 /*
  * pg_db_role_setting.c
  *		Routines to support manipulation of the pg_db_role_setting relation
  *
  * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
  *		src/backend/catalog/pg_db_role_setting.c
  */
 #include "postgres.h"

 #include "access/genam.h"
 #include "access/heapam.h"
 #include "access/htup_details.h"
 #include "access/tableam.h"
 #include "catalog/indexing.h"
 #include "catalog/objectaccess.h"
 #include "catalog/pg_db_role_setting.h"
 #include "utils/fmgroids.h"
 #include "utils/rel.h"

 #include "catalog/heap.h"
 #include "catalog/pg_authid.h"
 #include "catalog/pg_database.h"
 #include "cdb/cdbdisp_query.h"
 #include "cdb/cdbvars.h"
 #include "utils/builtins.h"
 #include "utils/syscache.h"

 void
 AlterSetting(Oid databaseid, Oid roleid, VariableSetStmt *setstmt)
 {
 	char	   *valuestr;
 	HeapTuple	tuple;
 	Relation	rel;
 	ScanKeyData scankey[2];
 	SysScanDesc scan;

 	valuestr = ExtractSetVariableArgs(setstmt);

 	/* Get the old tuple, if any. */

 	rel = table_open(DbRoleSettingRelationId, RowExclusiveLock);
 	ScanKeyInit(&scankey[0],
 				Anum_pg_db_role_setting_setdatabase,
 				BTEqualStrategyNumber, F_OIDEQ,
 				ObjectIdGetDatum(databaseid));
 	ScanKeyInit(&scankey[1],
 				Anum_pg_db_role_setting_setrole,
 				BTEqualStrategyNumber, F_OIDEQ,
 				ObjectIdGetDatum(roleid));
 	scan = systable_beginscan(rel, DbRoleSettingDatidRolidIndexId, true,
 							  NULL, 2, scankey);
 	tuple = systable_getnext(scan);

 	/*
 	 * There are three cases:
 	 *
 	 * - in RESET ALL, request GUC to reset the settings array and update the
 	 * catalog if there's anything left, delete it otherwise
 	 *
 	 * - in other commands, if there's a tuple in pg_db_role_setting, update
 	 * it; if it ends up empty, delete it
 	 *
 	 * - otherwise, insert a new pg_db_role_setting tuple, but only if the
 	 * command is not RESET
 	 */
 	if (setstmt->kind == VAR_RESET_ALL)
 	{
 		if (HeapTupleIsValid(tuple))
 		{
 			ArrayType  *new = NULL;
 			Datum		datum;
 			bool		isnull;

 			datum = heap_getattr(tuple, Anum_pg_db_role_setting_setconfig,
 								 RelationGetDescr(rel), &isnull);

 			if (!isnull)
 				new = GUCArrayReset(DatumGetArrayTypeP(datum));

 			if (new)
 			{
 				Datum		repl_val[Natts_pg_db_role_setting];
 				bool		repl_null[Natts_pg_db_role_setting];
 				bool		repl_repl[Natts_pg_db_role_setting];
 				HeapTuple	newtuple;

 				memset(repl_repl, false, sizeof(repl_repl));

 				repl_val[Anum_pg_db_role_setting_setconfig - 1] =
 					PointerGetDatum(new);
 				repl_repl[Anum_pg_db_role_setting_setconfig - 1] = true;
 				repl_null[Anum_pg_db_role_setting_setconfig - 1] = false;

 				newtuple = heap_modify_tuple(tuple, RelationGetDescr(rel),
 											 repl_val, repl_null, repl_repl);
 				CatalogTupleUpdate(rel, &tuple->t_self, newtuple);
 			}
 			else
 				CatalogTupleDelete(rel, &tuple->t_self);
 		}
 	}
 	else if (HeapTupleIsValid(tuple))
 	{
 		Datum		repl_val[Natts_pg_db_role_setting];
 		bool		repl_null[Natts_pg_db_role_setting];
 		bool		repl_repl[Natts_pg_db_role_setting];
 		HeapTuple	newtuple;
 		Datum		datum;
 		bool		isnull;
 		ArrayType  *a;

 		memset(repl_repl, false, sizeof(repl_repl));
 		repl_repl[Anum_pg_db_role_setting_setconfig - 1] = true;
 		repl_null[Anum_pg_db_role_setting_setconfig - 1] = false;

 		/* Extract old value of setconfig */
 		datum = heap_getattr(tuple, Anum_pg_db_role_setting_setconfig,
 							 RelationGetDescr(rel), &isnull);
 		a = isnull ? NULL : DatumGetArrayTypeP(datum);

 		/* Update (valuestr is NULL in RESET cases) */
 		if (valuestr)
 			a = GUCArrayAdd(a, setstmt->name, valuestr);
 		else
 			a = GUCArrayDelete(a, setstmt->name);

 		if (a)
 		{
 			repl_val[Anum_pg_db_role_setting_setconfig - 1] =
 				PointerGetDatum(a);

 			newtuple = heap_modify_tuple(tuple, RelationGetDescr(rel),
 										 repl_val, repl_null, repl_repl);
 			CatalogTupleUpdate(rel, &tuple->t_self, newtuple);
 		}
 		else
 			CatalogTupleDelete(rel, &tuple->t_self);
 	}
 	else if (valuestr)
 	{
 		/* non-null valuestr means it's not RESET, so insert a new tuple */
 		HeapTuple	newtuple;
 		Datum		values[Natts_pg_db_role_setting];
 		bool		nulls[Natts_pg_db_role_setting];
 		ArrayType  *a;

 		memset(nulls, false, sizeof(nulls));

 		a = GUCArrayAdd(NULL, setstmt->name, valuestr);

 		values[Anum_pg_db_role_setting_setdatabase - 1] =
 			ObjectIdGetDatum(databaseid);
 		values[Anum_pg_db_role_setting_setrole - 1] = ObjectIdGetDatum(roleid);
 		values[Anum_pg_db_role_setting_setconfig - 1] = PointerGetDatum(a);
 		newtuple = heap_form_tuple(RelationGetDescr(rel), values, nulls);

 		CatalogTupleInsert(rel, newtuple);
 	}

 	InvokeObjectPostAlterHookArg(DbRoleSettingRelationId,
 								 databaseid, 0, roleid, false);

 	systable_endscan(scan);

 	/* update pg_stat_last_shoperation for metadata tracking */
 	if (Gp_role == GP_ROLE_DISPATCH)
 	{
 		char	   *alter_subtype;

 		if (setstmt->kind == VAR_RESET_ALL)
 			alter_subtype = "RESET ALL";
 		else if (setstmt->kind == VAR_RESET)
 			alter_subtype = "RESET";
 		else
 			alter_subtype = "SET";

 		/* roleoid is only valid for ALTER ROLE */
 		MetaTrackUpdObject(DatabaseRelationId,
 						   OidIsValid(roleid) ? roleid : databaseid,
 						   GetUserId(),
 						   "ALTER", alter_subtype);
 	}

 	if (Gp_role == GP_ROLE_DISPATCH)
 	{
 		StringInfoData buffer;
 		char	   *rolename;
 		char	   *dbname;
 		HeapTuple	htup;

 		if (roleid)
 		{
 			htup = SearchSysCache1(AUTHOID, roleid);
 			if (!HeapTupleIsValid(htup))
 				elog(ERROR, "cache lookup failed for role %u", roleid);
 			rolename = pstrdup(NameStr(((Form_pg_authid) GETSTRUCT(htup))->rolname));
 			ReleaseSysCache(htup);
 		}
 		else
 			rolename = NULL;

 		if (databaseid)
 		{
 			htup = SearchSysCache1(DATABASEOID, databaseid);
 			if (!htup)
 				elog(ERROR, "cache lookup failed for database %u", databaseid);
 			dbname = pstrdup(NameStr(((Form_pg_database) GETSTRUCT(htup))->datname));
 			ReleaseSysCache(htup);
 		}
 		else
 			dbname = NULL;

 		initStringInfo(&buffer);

 		if (databaseid && roleid)
 			appendStringInfo(&buffer, "ALTER ROLE %s IN DATABASE %s ",
 							 quote_identifier(rolename), quote_identifier(dbname));
 		else if (roleid)
 			appendStringInfo(&buffer, "ALTER ROLE %s ",
 							 quote_identifier(rolename));
 		else if (databaseid)
 			appendStringInfo(&buffer, "ALTER DATABASE %s ",
 							 quote_identifier(dbname));
 		else
 			appendStringInfo(&buffer, "ALTER ROLE ALL ");

 		if (setstmt->kind ==  VAR_RESET_ALL)
 			appendStringInfo(&buffer, "RESET ALL");
 		else if (valuestr == NULL)
 			appendStringInfo(&buffer, "RESET %s", quote_identifier(setstmt->name));
 		else if (setstmt->kind ==  VAR_SET_CURRENT)
 			appendStringInfo(&buffer, "SET %s TO %s", quote_identifier(setstmt->name), quote_literal_cstr(valuestr));
 		else
 		{
 			ListCell   *l;
 			bool		first;

 			appendStringInfo(&buffer, "SET %s TO ", quote_identifier(setstmt->name));

 			/* Parse string into list of identifiers */
 			first = true;
 			foreach(l, setstmt->args)
 			{
 				A_Const	   *arg = (A_Const *) lfirst(l);

 				if (!first)
 					appendStringInfo(&buffer, ",");
 				first = false;

 				switch (nodeTag(&arg->val))
 				{
 					case T_Integer:
 						appendStringInfo(&buffer, "%d", intVal(&arg->val));
 						break;
 					case T_Float:
 						/* represented as a string, so just copy it */
 						appendStringInfoString(&buffer, strVal(&arg->val));
 						break;
 					case T_String:
 						appendStringInfoString(&buffer, quote_literal_cstr(strVal(&arg->val)));
 						break;
 					default:
 						elog(ERROR, "unexpected constant type: %d", nodeTag(&arg->val));
 				}
 			}
 		}

 		CdbDispatchCommand(buffer.data,
 						   DF_CANCEL_ON_ERROR|
 						   DF_NEED_TWO_PHASE|
 						   DF_WITH_SNAPSHOT,
 						   NULL);

 		pfree(buffer.data);
 	}

 	/* Close pg_db_role_setting, but keep lock till commit */
 	table_close(rel, NoLock);
 }

 /*
  * Drop some settings from the catalog.  These can be for a particular
  * database, or for a particular role.  (It is of course possible to do both
  * too, but it doesn't make sense for current uses.)
  */
 void
 DropSetting(Oid databaseid, Oid roleid)
 {
 	Relation	relsetting;
 	TableScanDesc scan;
 	ScanKeyData keys[2];
 	HeapTuple	tup;
 	int			numkeys = 0;

 	relsetting = table_open(DbRoleSettingRelationId, RowExclusiveLock);

 	if (OidIsValid(databaseid))
 	{
 		ScanKeyInit(&keys[numkeys],
 					Anum_pg_db_role_setting_setdatabase,
 					BTEqualStrategyNumber,
 					F_OIDEQ,
 					ObjectIdGetDatum(databaseid));
 		numkeys++;
 	}
 	if (OidIsValid(roleid))
 	{
 		ScanKeyInit(&keys[numkeys],
 					Anum_pg_db_role_setting_setrole,
 					BTEqualStrategyNumber,
 					F_OIDEQ,
 					ObjectIdGetDatum(roleid));
 		numkeys++;
 	}

 	scan = table_beginscan_catalog(relsetting, numkeys, keys);
 	while (HeapTupleIsValid(tup = heap_getnext(scan, ForwardScanDirection)))
 	{
 		CatalogTupleDelete(relsetting, &tup->t_self);
 	}
 	table_endscan(scan);

 	table_close(relsetting, RowExclusiveLock);
 }

 /*
  * Scan pg_db_role_setting looking for applicable settings, and load them on
  * the current process.
  *
  * relsetting is pg_db_role_setting, already opened and locked.
  *
  * Note: we only consider setting for the exact databaseid/roleid combination.
  * This probably needs to be called more than once, with InvalidOid passed as
  * databaseid/roleid.
  */
 void
 ApplySetting(Snapshot snapshot, Oid databaseid, Oid roleid,
 			 Relation relsetting, GucSource source)
 {
 	SysScanDesc scan;
 	ScanKeyData keys[2];
 	HeapTuple	tup;

 	ScanKeyInit(&keys[0],
 				Anum_pg_db_role_setting_setdatabase,
 				BTEqualStrategyNumber,
 				F_OIDEQ,
 				ObjectIdGetDatum(databaseid));
 	ScanKeyInit(&keys[1],
 				Anum_pg_db_role_setting_setrole,
 				BTEqualStrategyNumber,
 				F_OIDEQ,
 				ObjectIdGetDatum(roleid));

 	scan = systable_beginscan(relsetting, DbRoleSettingDatidRolidIndexId, true,
 							  snapshot, 2, keys);
 	while (HeapTupleIsValid(tup = systable_getnext(scan)))
 	{
 		bool		isnull;
 		Datum		datum;

 		datum = heap_getattr(tup, Anum_pg_db_role_setting_setconfig,
 							 RelationGetDescr(relsetting), &isnull);
 		if (!isnull)
 		{
 			ArrayType  *a = DatumGetArrayTypeP(datum);

 			/*
 			 * We process all the options at SUSET level.  We assume that the
 			 * right to insert an option into pg_db_role_setting was checked
 			 * when it was inserted.
 			 */
 			ProcessGUCArray(a, PGC_SUSET, source, GUC_ACTION_SET);
 		}
 	}

 	systable_endscan(scan);
 }
	/*
	* pg_db_role_setting.c
	* Routines to support manipulation of the pg_db_role_setting relation
	*
	* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
	* Portions Copyright (c) 1994, Regents of the University of California
	*
	* IDENTIFICATION
	* src/backend/catalog/pg_db_role_setting.c
	*/
	#include "postgres.h"

	#include "access/genam.h"
	#include "access/heapam.h"
	#include "access/htup_details.h"
	#include "access/tableam.h"
	#include "catalog/indexing.h"
	#include "catalog/objectaccess.h"
	#include "catalog/pg_db_role_setting.h"
	#include "utils/fmgroids.h"
	#include "utils/rel.h"

	#include "catalog/heap.h"
	#include "catalog/pg_authid.h"
	#include "catalog/pg_database.h"
	#include "cdb/cdbdisp_query.h"
	#include "cdb/cdbvars.h"
	#include "utils/builtins.h"
	#include "utils/syscache.h"

	void
	AlterSetting(Oid databaseid, Oid roleid, VariableSetStmt *setstmt)
	{
	char *valuestr;
	HeapTuple tuple;
	Relation rel;
	ScanKeyData scankey[2];
	SysScanDesc scan;

	valuestr = ExtractSetVariableArgs(setstmt);

	/* Get the old tuple, if any. */

	rel = table_open(DbRoleSettingRelationId, RowExclusiveLock);
	ScanKeyInit(&scankey[0],
	Anum_pg_db_role_setting_setdatabase,
	BTEqualStrategyNumber, F_OIDEQ,
	ObjectIdGetDatum(databaseid));
	ScanKeyInit(&scankey[1],
	Anum_pg_db_role_setting_setrole,
	BTEqualStrategyNumber, F_OIDEQ,
	ObjectIdGetDatum(roleid));
	scan = systable_beginscan(rel, DbRoleSettingDatidRolidIndexId, true,
	NULL, 2, scankey);
	tuple = systable_getnext(scan);

	/*
	* There are three cases:
	*
	* - in RESET ALL, request GUC to reset the settings array and update the
	* catalog if there's anything left, delete it otherwise
	*
	* - in other commands, if there's a tuple in pg_db_role_setting, update
	* it; if it ends up empty, delete it
	*
	* - otherwise, insert a new pg_db_role_setting tuple, but only if the
	* command is not RESET
	*/
	if (setstmt->kind == VAR_RESET_ALL)
	{
	if (HeapTupleIsValid(tuple))
	{
	ArrayType *new = NULL;
	Datum datum;
	bool isnull;

	datum = heap_getattr(tuple, Anum_pg_db_role_setting_setconfig,
	RelationGetDescr(rel), &isnull);

	if (!isnull)
	new = GUCArrayReset(DatumGetArrayTypeP(datum));

	if (new)
	{
	Datum repl_val[Natts_pg_db_role_setting];
	bool repl_null[Natts_pg_db_role_setting];
	bool repl_repl[Natts_pg_db_role_setting];
	HeapTuple newtuple;

	memset(repl_repl, false, sizeof(repl_repl));

	repl_val[Anum_pg_db_role_setting_setconfig - 1] =
	PointerGetDatum(new);
	repl_repl[Anum_pg_db_role_setting_setconfig - 1] = true;
	repl_null[Anum_pg_db_role_setting_setconfig - 1] = false;

	newtuple = heap_modify_tuple(tuple, RelationGetDescr(rel),
	repl_val, repl_null, repl_repl);
	CatalogTupleUpdate(rel, &tuple->t_self, newtuple);
	}
	else
	CatalogTupleDelete(rel, &tuple->t_self);
	}
	}
	else if (HeapTupleIsValid(tuple))
	{
	Datum repl_val[Natts_pg_db_role_setting];
	bool repl_null[Natts_pg_db_role_setting];
	bool repl_repl[Natts_pg_db_role_setting];
	HeapTuple newtuple;
	Datum datum;
	bool isnull;
	ArrayType *a;

	memset(repl_repl, false, sizeof(repl_repl));
	repl_repl[Anum_pg_db_role_setting_setconfig - 1] = true;
	repl_null[Anum_pg_db_role_setting_setconfig - 1] = false;

	/* Extract old value of setconfig */
	datum = heap_getattr(tuple, Anum_pg_db_role_setting_setconfig,
	RelationGetDescr(rel), &isnull);
	a = isnull ? NULL : DatumGetArrayTypeP(datum);

	/* Update (valuestr is NULL in RESET cases) */
	if (valuestr)
	a = GUCArrayAdd(a, setstmt->name, valuestr);
	else
	a = GUCArrayDelete(a, setstmt->name);

	if (a)
	{
	repl_val[Anum_pg_db_role_setting_setconfig - 1] =
	PointerGetDatum(a);

	newtuple = heap_modify_tuple(tuple, RelationGetDescr(rel),
	repl_val, repl_null, repl_repl);
	CatalogTupleUpdate(rel, &tuple->t_self, newtuple);
	}
	else
	CatalogTupleDelete(rel, &tuple->t_self);
	}
	else if (valuestr)
	{
	/* non-null valuestr means it's not RESET, so insert a new tuple */
	HeapTuple newtuple;
	Datum values[Natts_pg_db_role_setting];
	bool nulls[Natts_pg_db_role_setting];
	ArrayType *a;

	memset(nulls, false, sizeof(nulls));

	a = GUCArrayAdd(NULL, setstmt->name, valuestr);

	values[Anum_pg_db_role_setting_setdatabase - 1] =
	ObjectIdGetDatum(databaseid);
	values[Anum_pg_db_role_setting_setrole - 1] = ObjectIdGetDatum(roleid);
	values[Anum_pg_db_role_setting_setconfig - 1] = PointerGetDatum(a);
	newtuple = heap_form_tuple(RelationGetDescr(rel), values, nulls);

	CatalogTupleInsert(rel, newtuple);
	}

	InvokeObjectPostAlterHookArg(DbRoleSettingRelationId,
	databaseid, 0, roleid, false);

	systable_endscan(scan);

	/* update pg_stat_last_shoperation for metadata tracking */
	if (Gp_role == GP_ROLE_DISPATCH)
	{
	char *alter_subtype;

	if (setstmt->kind == VAR_RESET_ALL)
	alter_subtype = "RESET ALL";
	else if (setstmt->kind == VAR_RESET)
	alter_subtype = "RESET";
	else
	alter_subtype = "SET";

	/* roleoid is only valid for ALTER ROLE */
	MetaTrackUpdObject(DatabaseRelationId,
	OidIsValid(roleid) ? roleid : databaseid,
	GetUserId(),
	"ALTER", alter_subtype);
	}

	if (Gp_role == GP_ROLE_DISPATCH)
	{
	StringInfoData buffer;
	char *rolename;
	char *dbname;
	HeapTuple htup;

	if (roleid)
	{
	htup = SearchSysCache1(AUTHOID, roleid);
	if (!HeapTupleIsValid(htup))
	elog(ERROR, "cache lookup failed for role %u", roleid);
	rolename = pstrdup(NameStr(((Form_pg_authid) GETSTRUCT(htup))->rolname));
	ReleaseSysCache(htup);
	}
	else
	rolename = NULL;

	if (databaseid)
	{
	htup = SearchSysCache1(DATABASEOID, databaseid);
	if (!htup)
	elog(ERROR, "cache lookup failed for database %u", databaseid);
	dbname = pstrdup(NameStr(((Form_pg_database) GETSTRUCT(htup))->datname));
	ReleaseSysCache(htup);
	}
	else
	dbname = NULL;

	initStringInfo(&buffer);

	if (databaseid && roleid)
	appendStringInfo(&buffer, "ALTER ROLE %s IN DATABASE %s ",
	quote_identifier(rolename), quote_identifier(dbname));
	else if (roleid)
	appendStringInfo(&buffer, "ALTER ROLE %s ",
	quote_identifier(rolename));
	else if (databaseid)
	appendStringInfo(&buffer, "ALTER DATABASE %s ",
	quote_identifier(dbname));
	else
	appendStringInfo(&buffer, "ALTER ROLE ALL ");

	if (setstmt->kind == VAR_RESET_ALL)
	appendStringInfo(&buffer, "RESET ALL");
	else if (valuestr == NULL)
	appendStringInfo(&buffer, "RESET %s", quote_identifier(setstmt->name));
	else if (setstmt->kind == VAR_SET_CURRENT)
	appendStringInfo(&buffer, "SET %s TO %s", quote_identifier(setstmt->name), quote_literal_cstr(valuestr));
	else
	{
	ListCell *l;
	bool first;

	appendStringInfo(&buffer, "SET %s TO ", quote_identifier(setstmt->name));

	/* Parse string into list of identifiers */
	first = true;
	foreach(l, setstmt->args)
	{
	A_Const arg = (A_Const ) lfirst(l);

	if (!first)
	appendStringInfo(&buffer, ",");
	first = false;

	switch (nodeTag(&arg->val))
	{
	case T_Integer:
	appendStringInfo(&buffer, "%d", intVal(&arg->val));
	break;
	case T_Float:
	/* represented as a string, so just copy it */
	appendStringInfoString(&buffer, strVal(&arg->val));
	break;
	case T_String:
	appendStringInfoString(&buffer, quote_literal_cstr(strVal(&arg->val)));
	break;
	default:
	elog(ERROR, "unexpected constant type: %d", nodeTag(&arg->val));
	}
	}
	}

	CdbDispatchCommand(buffer.data,
	DF_CANCEL_ON_ERROR\|
	DF_NEED_TWO_PHASE\|
	DF_WITH_SNAPSHOT,
	NULL);

	pfree(buffer.data);
	}

	/* Close pg_db_role_setting, but keep lock till commit */
	table_close(rel, NoLock);
	}

	/*
	* Drop some settings from the catalog. These can be for a particular
	* database, or for a particular role. (It is of course possible to do both
	* too, but it doesn't make sense for current uses.)
	*/
	void
	DropSetting(Oid databaseid, Oid roleid)
	{
	Relation relsetting;
	TableScanDesc scan;
	ScanKeyData keys[2];
	HeapTuple tup;
	int numkeys = 0;

	relsetting = table_open(DbRoleSettingRelationId, RowExclusiveLock);

	if (OidIsValid(databaseid))
	{
	ScanKeyInit(&keys[numkeys],
	Anum_pg_db_role_setting_setdatabase,
	BTEqualStrategyNumber,
	F_OIDEQ,
	ObjectIdGetDatum(databaseid));
	numkeys++;
	}
	if (OidIsValid(roleid))
	{
	ScanKeyInit(&keys[numkeys],
	Anum_pg_db_role_setting_setrole,
	BTEqualStrategyNumber,
	F_OIDEQ,
	ObjectIdGetDatum(roleid));
	numkeys++;
	}

	scan = table_beginscan_catalog(relsetting, numkeys, keys);
	while (HeapTupleIsValid(tup = heap_getnext(scan, ForwardScanDirection)))
	{
	CatalogTupleDelete(relsetting, &tup->t_self);
	}
	table_endscan(scan);

	table_close(relsetting, RowExclusiveLock);
	}

	/*
	* Scan pg_db_role_setting looking for applicable settings, and load them on
	* the current process.
	*
	* relsetting is pg_db_role_setting, already opened and locked.
	*
	* Note: we only consider setting for the exact databaseid/roleid combination.
	* This probably needs to be called more than once, with InvalidOid passed as
	* databaseid/roleid.
	*/
	void
	ApplySetting(Snapshot snapshot, Oid databaseid, Oid roleid,
	Relation relsetting, GucSource source)
	{
	SysScanDesc scan;
	ScanKeyData keys[2];
	HeapTuple tup;

	ScanKeyInit(&keys[0],
	Anum_pg_db_role_setting_setdatabase,
	BTEqualStrategyNumber,
	F_OIDEQ,
	ObjectIdGetDatum(databaseid));
	ScanKeyInit(&keys[1],
	Anum_pg_db_role_setting_setrole,
	BTEqualStrategyNumber,
	F_OIDEQ,
	ObjectIdGetDatum(roleid));

	scan = systable_beginscan(relsetting, DbRoleSettingDatidRolidIndexId, true,
	snapshot, 2, keys);
	while (HeapTupleIsValid(tup = systable_getnext(scan)))
	{
	bool isnull;
	Datum datum;

	datum = heap_getattr(tup, Anum_pg_db_role_setting_setconfig,
	RelationGetDescr(relsetting), &isnull);
	if (!isnull)
	{
	ArrayType *a = DatumGetArrayTypeP(datum);

	/*
	* We process all the options at SUSET level. We assume that the
	* right to insert an option into pg_db_role_setting was checked
	* when it was inserted.
	*/
	ProcessGUCArray(a, PGC_SUSET, source, GUC_ACTION_SET);
	}
	}

	systable_endscan(scan);
	}