pg_shdepend.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

									   sdepForm->deptype, 0);
		}
		else if (sdepForm->dbid == InvalidOid)
		{
			numSharedDeps++;
			if (++totalDeps <= MAX_REPORTED_DEPS)
				storeObjectDescription(&descs, SHARED_OBJECT, &object,
									   sdepForm->deptype, 0);
		}
		else
		{
			/* It's not local nor shared, so it must be remote. */
			remoteDep  *dep;
			bool		stored = false;

			/*
			 * XXX this info is kept on a simple List.	Maybe it's not good
			 * for performance, but using a hash table seems needlessly
			 * complex.  The expected number of databases is not high anyway,
			 * I suppose.
			 */
			foreach(cell, remDeps)
			{
				dep = lfirst(cell);
				if (dep->dbOid == sdepForm->dbid)
				{
					dep->count++;
					stored = true;
					break;
				}
			}
			if (!stored)
			{
				dep = (remoteDep *) palloc(sizeof(remoteDep));
				dep->dbOid = sdepForm->dbid;
				dep->count = 1;
				remDeps = lappend(remDeps, dep);
				totalDeps++;
			}
		}
	}

	systable_endscan(scan);

	heap_close(sdepRel, AccessShareLock);

	if (totalDeps > MAX_REPORTED_DEPS)
	{
		/*
		 * Report seems unreasonably long, so reduce it to per-database info
		 *
		 * Note: we don't ever suppress per-database totals, which should be
		 * OK as long as there aren't too many databases ...
		 */
		descs.len = 0;			/* reset to empty */
		descs.data[0] = '\0';

		if (numLocalDeps > 0)
		{
			appendStringInfo(&descs, _("%d objects in this database"),
							 numLocalDeps);
			if (numSharedDeps > 0)
				appendStringInfoChar(&descs, '\n');
		}
		if (numSharedDeps > 0)
			appendStringInfo(&descs, _("%d shared objects"),
							 numSharedDeps);
	}

	foreach(cell, remDeps)
	{
		remoteDep  *dep = lfirst(cell);

		object.classId = DatabaseRelationId;
		object.objectId = dep->dbOid;
		object.objectSubId = 0;

		storeObjectDescription(&descs, REMOTE_OBJECT, &object,
							   SHARED_DEPENDENCY_INVALID, dep->count);
	}

	list_free_deep(remDeps);

	if (descs.len == 0)
	{
		pfree(descs.data);
		return NULL;
	}

	return descs.data;
}

/*
 * copyTemplateDependencies
 *
 * Routine to create the initial shared dependencies of a new database.
 * We simply copy the dependencies from the template database.
 */
void
copyTemplateDependencies(Oid templateDbId, Oid newDbId)
{
	Relation	sdepRel;
	TupleDesc	sdepDesc;
	ScanKeyData key[1];
	SysScanDesc scan;
	HeapTuple	tup;
	CatalogIndexState indstate;
	Datum		values[Natts_pg_shdepend];
	bool		nulls[Natts_pg_shdepend];
	bool		replace[Natts_pg_shdepend];

	sdepRel = heap_open(SharedDependRelationId, RowExclusiveLock);
	sdepDesc = RelationGetDescr(sdepRel);

	indstate = CatalogOpenIndexes(sdepRel);

	/* Scan all entries with dbid = templateDbId */
	ScanKeyInit(&key[0],
				Anum_pg_shdepend_dbid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(templateDbId));

	scan = systable_beginscan(sdepRel, SharedDependDependerIndexId, true,
							  SnapshotNow, 1, key);

	/* Set up to copy the tuples except for inserting newDbId */
	memset(values, 0, sizeof(values));
	memset(nulls, false, sizeof(nulls));
	memset(replace, false, sizeof(replace));

	replace[Anum_pg_shdepend_dbid - 1] = true;
	values[Anum_pg_shdepend_dbid - 1] = ObjectIdGetDatum(newDbId);

	/*
	 * Copy the entries of the original database, changing the database Id to
	 * that of the new database.  Note that because we are not copying rows
	 * with dbId == 0 (ie, rows describing dependent shared objects) we won't
	 * copy the ownership dependency of the template database itself; this is
	 * what we want.
	 */
	while (HeapTupleIsValid(tup = systable_getnext(scan)))
	{
		HeapTuple	newtup;

		newtup = heap_modify_tuple(tup, sdepDesc, values, nulls, replace);
		simple_heap_insert(sdepRel, newtup);

		/* Keep indexes current */
		CatalogIndexInsert(indstate, newtup);

		heap_freetuple(newtup);
	}

	systable_endscan(scan);

	CatalogCloseIndexes(indstate);
	heap_close(sdepRel, RowExclusiveLock);
}

/*
 * dropDatabaseDependencies
 *
 * Delete pg_shdepend entries corresponding to a database that's being
 * dropped.
 */
void
dropDatabaseDependencies(Oid databaseId)
{
	Relation	sdepRel;
	ScanKeyData key[1];
	SysScanDesc scan;
	HeapTuple	tup;

	sdepRel = heap_open(SharedDependRelationId, RowExclusiveLock);

	/*
	 * First, delete all the entries that have the database Oid in the dbid
	 * field.
	 */
	ScanKeyInit(&key[0],
				Anum_pg_shdepend_dbid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(databaseId));
	/* We leave the other index fields unspecified */

	scan = systable_beginscan(sdepRel, SharedDependDependerIndexId, true,
							  SnapshotNow, 1, key);

	while (HeapTupleIsValid(tup = systable_getnext(scan)))
	{
		simple_heap_delete(sdepRel, &tup->t_self);
	}

	systable_endscan(scan);

	/* Now delete all entries corresponding to the database itself */
	shdepDropDependency(sdepRel, DatabaseRelationId, databaseId,
						InvalidOid, InvalidOid,
						SHARED_DEPENDENCY_INVALID);

	heap_close(sdepRel, RowExclusiveLock);
}

/*
 * deleteSharedDependencyRecordsFor
 *
 * Delete all pg_shdepend entries corresponding to an object that's being
 * dropped or modified.  The object is assumed to be either a shared object
 * or local to the current database (the classId tells us which).
 */
void
deleteSharedDependencyRecordsFor(Oid classId, Oid objectId)
{
	Relation	sdepRel;

	sdepRel = heap_open(SharedDependRelationId, RowExclusiveLock);

	shdepDropDependency(sdepRel, classId, objectId,
						InvalidOid, InvalidOid,
						SHARED_DEPENDENCY_INVALID);

	heap_close(sdepRel, RowExclusiveLock);
}

/*
 * shdepAddDependency
 *		Internal workhorse for inserting into pg_shdepend
 *
 * sdepRel must be the pg_shdepend relation, already opened and suitably
 * locked.
 */
static void
shdepAddDependency(Relation sdepRel, Oid classId, Oid objectId,
				   Oid refclassId, Oid refobjId,
				   SharedDependencyType deptype)
{
	HeapTuple	tup;
	Datum		values[Natts_pg_shdepend];
	bool		nulls[Natts_pg_shdepend];

	/*
	 * Make sure the object doesn't go away while we record the dependency on
	 * it.	DROP routines should lock the object exclusively before they check
	 * shared dependencies.
	 */
	shdepLockAndCheckObject(refclassId, refobjId);

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

	/*
	 * Form the new tuple and record the dependency.
	 */
	values[Anum_pg_shdepend_dbid - 1] = ObjectIdGetDatum(classIdGetDbId(classId));
	values[Anum_pg_shdepend_classid - 1] = ObjectIdGetDatum(classId);
	values[Anum_pg_shdepend_objid - 1] = ObjectIdGetDatum(objectId);

	values[Anum_pg_shdepend_refclassid - 1] = ObjectIdGetDatum(refclassId);
	values[Anum_pg_shdepend_refobjid - 1] = ObjectIdGetDatum(refobjId);
	values[Anum_pg_shdepend_deptype - 1] = CharGetDatum(deptype);

	tup = heap_form_tuple(sdepRel->rd_att, values, nulls);

	simple_heap_insert(sdepRel, tup);

	/* keep indexes current */
	CatalogUpdateIndexes(sdepRel, tup);

	/* clean up */
	heap_freetuple(tup);
}

/*
 * shdepDropDependency
 *		Internal workhorse for deleting entries from pg_shdepend.
 *
 * We drop entries having the following properties:
 *	dependent object is the one identified by classId/objectId
 *	if refclassId isn't InvalidOid, it must match the entry's refclassid
 *	if refobjId isn't InvalidOid, it must match the entry's refobjid
 *	if deptype isn't SHARED_DEPENDENCY_INVALID, it must match entry's deptype
 *
 * sdepRel must be the pg_shdepend relation, already opened and suitably
 * locked.
 */
static void
shdepDropDependency(Relation sdepRel, Oid classId, Oid objectId,
					Oid refclassId, Oid refobjId,
					SharedDependencyType deptype)
{
	ScanKeyData key[3];
	SysScanDesc scan;
	HeapTuple	tup;

	/* Scan for entries matching the dependent object */
	ScanKeyInit(&key[0],
				Anum_pg_shdepend_dbid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(classIdGetDbId(classId)));
	ScanKeyInit(&key[1],
				Anum_pg_shdepend_classid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(classId));
	ScanKeyInit(&key[2],
				Anum_pg_shdepend_objid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(objectId));

	scan = systable_beginscan(sdepRel, SharedDependDependerIndexId, true,
							  SnapshotNow, 3, key);

	while (HeapTupleIsValid(tup = systable_getnext(scan)))
	{
		Form_pg_shdepend shdepForm = (Form_pg_shdepend) GETSTRUCT(tup);

		/* Filter entries according to additional parameters */
		if (OidIsValid(refclassId) && shdepForm->refclassid != refclassId)
			continue;
		if (OidIsValid(refobjId) && shdepForm->refobjid != refobjId)
			continue;
		if (deptype != SHARED_DEPENDENCY_INVALID &&
			shdepForm->deptype != deptype)
			continue;

		/* OK, delete it */
		simple_heap_delete(sdepRel, &tup->t_self);
	}

	systable_endscan(scan);
}

/*
 * classIdGetDbId
 *
 * Get the database Id that should be used in pg_shdepend, given the OID
 * of the catalog containing the object.  For shared objects, it's 0
 * (InvalidOid); for all other objects, it's the current database Id.
 *
 * XXX it's awfully tempting to hard-wire this instead of doing a syscache
 * lookup ... but resist the temptation, unless you can prove it's a
 * bottleneck.
 */
static Oid
classIdGetDbId(Oid classId)
{
	Oid			dbId;
	HeapTuple	tup;

	tup = SearchSysCache(RELOID,
						 ObjectIdGetDatum(classId),
						 0, 0, 0);
	if (!HeapTupleIsValid(tup))
		elog(ERROR, "cache lookup failed for relation %u", classId);

	if (((Form_pg_class) GETSTRUCT(tup))->relisshared)
		dbId = InvalidOid;
	else
		dbId = MyDatabaseId;

	ReleaseSysCache(tup);

	return dbId;
}

/*
 * shdepLockAndCheckObject
 *
 * Lock the object that we are about to record a dependency on.
 * After it's locked, verify that it hasn't been dropped while we
 * weren't looking.  If the object has been dropped, this function
 * does not return!
 */
static void
shdepLockAndCheckObject(Oid classId, Oid objectId)
{
	/* AccessShareLock should be OK, since we are not modifying the object */
	LockSharedObject(classId, objectId, 0, AccessShareLock);

	/*
	 * We have to recognize sinval updates here, else our local syscache may
	 * still contain the object even if it was just dropped.
	 */
	AcceptInvalidationMessages();

	switch (classId)
	{
		case AuthIdRelationId:
			if (!SearchSysCacheExists(AUTHOID,
									  ObjectIdGetDatum(objectId),
									  0, 0, 0))
				ereport(ERROR,
						(errcode(ERRCODE_UNDEFINED_OBJECT),
						 errmsg("role %u was concurrently dropped",
								objectId)));
			break;

			/*
			 * Currently, this routine need not support any other shared
			 * object types besides roles.	If we wanted to record explicit
			 * dependencies on databases or tablespaces, we'd need code along
			 * these lines:
			 */
#ifdef NOT_USED
		case TableSpaceRelationId:
			{
				/* For lack of a syscache on pg_tablespace, do this: */
				char	   *tablespace = get_tablespace_name(objectId);

				if (tablespace == NULL)
					ereport(ERROR,
							(errcode(ERRCODE_UNDEFINED_OBJECT),
							 errmsg("tablespace %u was concurrently dropped",
									objectId)));
				pfree(tablespace);
				break;
			}
#endif

		default:
			elog(ERROR, "unrecognized shared classId: %u", classId);
	}
}


/*
 * storeObjectDescription
 *		Append the description of a dependent object to "descs"
 *
 * While searching for dependencies of a shared object, we stash the
 * descriptions of dependent objects we find in a single string, which we
 * later pass to ereport() in the DETAIL field when somebody attempts to
 * drop a referenced shared object.
 *
 * When type is LOCAL_OBJECT or SHARED_OBJECT, we expect object to be the
 * dependent object, deptype is the dependency type, and count is not used.
 * When type is REMOTE_OBJECT, we expect object to be the database object,
 * and count to be nonzero; deptype is not used in this case.
 */
static void
storeObjectDescription(StringInfo descs, objectType type,
					   ObjectAddress *object,
					   SharedDependencyType deptype,
					   int count)
{
	char	   *objdesc = getObjectDescription(object);

	/* separate entries with a newline */
	if (descs->len != 0)
		appendStringInfoChar(descs, '\n');

	switch (type)
	{
		case LOCAL_OBJECT:
		case SHARED_OBJECT:
			if (deptype == SHARED_DEPENDENCY_OWNER)
				appendStringInfo(descs, _("owner of %s"), objdesc);
			else if (deptype == SHARED_DEPENDENCY_ACL)
				appendStringInfo(descs, _("access to %s"), objdesc);
			else
				elog(ERROR, "unrecognized dependency type: %d",
					 (int) deptype);
			break;

		case REMOTE_OBJECT:
			/* translator: %s will always be "database %s" */
			appendStringInfo(descs, _("%d objects in %s"), count, objdesc);
			break;

		default:
			elog(ERROR, "unrecognized object type: %d", type);
	}

	pfree(objdesc);
}


/*
 * isSharedObjectPinned
 *		Return whether a given shared object has a SHARED_DEPENDENCY_PIN entry.
 *
 * sdepRel must be the pg_shdepend relation, already opened and suitably
 * locked.
 */
static bool
isSharedObjectPinned(Oid classId, Oid objectId, Relation sdepRel)
{
	bool		result = false;
	ScanKeyData key[2];
	SysScanDesc scan;
	HeapTuple	tup;

	ScanKeyInit(&key[0],
				Anum_pg_shdepend_refclassid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(classId));
	ScanKeyInit(&key[1],
				Anum_pg_shdepend_refobjid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(objectId));

	scan = systable_beginscan(sdepRel, SharedDependReferenceIndexId, true,
							  SnapshotNow, 2, key);

	/*
	 * Since we won't generate additional pg_shdepend entries for pinned
	 * objects, there can be at most one entry referencing a pinned object.
	 * Hence, it's sufficient to look at the first returned tuple; we don't
	 * need to loop.
	 */
	tup = systable_getnext(scan);
	if (HeapTupleIsValid(tup))
	{
		Form_pg_shdepend shdepForm = (Form_pg_shdepend) GETSTRUCT(tup);

		if (shdepForm->deptype == SHARED_DEPENDENCY_PIN)
			result = true;
	}

	systable_endscan(scan);

	return result;
}