DB.py

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"""Database objects

$Id: DB.py,v 1.8 1999/06/29 18:27:55 jim Exp $"""
__version__='$Revision: 1.8 $'[11:-2]

import cPickle, cStringIO, sys, POSException
from Connection import Connection
from bpthread import allocate_lock
from Transaction import Transaction
from referencesf import referencesf

StringType=type('')

class DB:
    """The Object Database

    The Object database coordinates access to and interaction of one
    or more connections, which manage object spaces.  Most of the actual work
    of managing objects is done by the connections.
    """

    def __init__(self, storage,
                 pool_size=7,
                 cache_size=400,
                 cache_deactivate_after=60,
                 version_pool_size=3,
                 version_cache_size=100,
                 version_cache_deactivate_after=10,
                 ):
        """Create an object database.

        The storage for the object database must be passed in.
        Optional arguments are:

        pool_size -- The size of the pool of object spaces.

        """
        self._storage=storage
        storage.registerDB(self, None)
        try: storage.load('\0\0\0\0\0\0\0\0','')
        except:
            import PersistentMapping
            file=cStringIO.StringIO()
            p=cPickle.Pickler(file,1)
            p.dump((PersistentMapping.PersistentMapping,None))
            p.dump({'_container': {}})
            t=Transaction()
            t.description='initial database creation'
            storage.tpc_begin(t)
            storage.store('\0\0\0\0\0\0\0\0', None, file.getvalue(), '', t)
            storage.tpc_finish(t)

        # Allocate locks:
        l=allocate_lock()
        self._a=l.acquire
        self._r=l.release

        self._pools={},[]
        self._temps=[]

        self._pool_size=pool_size
        self._cache_size=cache_size
        self._cache_deactivate_after=cache_deactivate_after
        self._version_pool_size=version_pool_size
        self._version_cache_size=version_cache_size
        self._version_cache_deactivate_after=version_cache_deactivate_after

        # Pass through methods:
        for m in ('history', 'modifiedInVersion',
                  'supportsUndo', 'supportsVersions',
                  'undo', 'undoLog',
                  'versionEmpty', 'versions'):
            setattr(self, m, getattr(storage, m))
        

    def _cacheMean(self, attr):
        m=[0,0]
        def f(con, m=m):
            t=getattr(con._cache,attr)
            m[0]=m[0]+t
            m[1]=m[1]+1

        self._connectionMap(f)
        if m[1]: m=m[0]/m[1]
        else: m=None
        return m

    def _classFactory(self, connection, location, name,
                      _silly=('__doc__',), _globals={}):
        return getattr(__import__(location, _globals, _globals, _silly),
                       name)
            
    def _closeConnection(self, connection):
        """Return a connection to the pool"""
        self._a()
        try:
            version=connection._version
            pools,pooll=self._pools
            pool, allocated, pool_lock = pools[version]
            pool.append(connection)
            if len(pool)==1:
                # Pool now usable again, unlock it.
                pool_lock.release()
        finally: self._r()
        
    def _connectionMap(self, f):
        self._a()
        try:
            pools,pooll=self._pools
            for pool, allocated in pooll:
                for cc in allocated: f(cc)

            temps=self._temps
            if temps:
                t=[]
                for cc in temps:
                    if rc(cc) > 3: f(cc)
                self._temps=t
        finally: self._r()

    def abortVersion(self, version):
        AbortVersion(self, version)

    def cacheDetail(self):
        """Return information on objects in the various caches

        Organized by class."""

        detail={}
        def f(con,detail=detail,have_detail=detail.has_key):
            for oid, ob in con._cache.items():
                c="%s.%s" % (ob.__class__.__module__, ob.__class__.__name__)
                if have_detail(c): detail[c]=detail[c]+1
                else: detail[c]=1
        
        self._connectionMap(f)
        detail=detail.items()
        detail.sort()
        return detail

    def cacheExtremeDetail(self):
        detail=[]
        def f(con, detail=detail, rc=sys.getrefcount):
            for oid, ob in con._cache.items():
                id=oid
                if hasattr(ob,'__dict__'):
                    d=ob.__dict__
                    if d.has_key('id'):
                        id="%s (%s)" % (oid, d['id'])
                    elif d.has_key('__name__'):
                        id="%s (%s)" % (oid, d['__name__'])
    
                detail.append({
                    'oid': id,
                    'klass': "%s.%s" % (ob.__class__.__module__,
                                        ob.__class__.__name__),
                    'rc': rc(ob)-4,
                    'references': con.references(oid),
                    })

        self._connectionMap(f)
        return detail

    def cacheFullSweep(self, value):
        self._connectionMap(lambda c, v=value: c._cache.full_sweep(v))

    def cacheLastGCTime(self):
        m=[0]
        def f(con, m=m):
            t=con._cache.cache_last_gc_time
            if t > m[0]: m[0]=t

        self._connectionMap(f)
        return m[0]

    def cacheMinimize(self, value):
        self._connectionMap(lambda c, v=value: c._cache.minimize(v))

    def cacheMeanAge(self): return self._cacheMean('cache_mean_age')
    def cacheMeanDeac(self): return self._cacheMean('cache_mean_deac')
    def cacheMeanDeal(self): return self._cacheMean('cache_mean_deal')

    def cacheSize(self):
        m=[0]
        def f(con, m=m):
            m[0]=m[0]+len(con._cache)

        self._connectionMap(f)
        return m[0]

    def close(self): self._storage.close()

    def commitVersion(self, source, destination=''):
        CommitVersion(self, source, destination)

    def exportFile(self, oid, file=None):
        raise 'Not yet implemented'
                           
    def getCacheDeactivateAfter(self): return self._cache_deactivate_after
    def getCacheSize(self): return self._cache_size

    def getName(self): return self._storage.getName()

    def getPoolSize(self): return self._pool_size

    def getSize(self): return self._storage.getSize()

    def getVersionCacheDeactivateAfter(self):
        return self._version_cache_deactivate_after
    def getVersionCacheSize(self): return self._version_cache_size

    def getVersionPoolSize(self): return self._version_pool_size

    def importFile(self, file):
        raise 'Not yet implemented'

    def invalidate(self, oid, connection=None, version='',
                   rc=sys.getrefcount):
        """Invalidate references to a given oid.

        This is used to indicate that one of the connections has committed a
        change to the object.  The connection commiting the change should be
        passed in to prevent useless (but harmless) messages to the
        connection.
        """
        if connection is not None: version=connection._version
        self._a()
        try:
            pools,pooll=self._pools
            for pool, allocated in pooll:
                for cc in allocated:
                    if (cc is not connection and
                        (not version or cc._version==version)):
                        if rc(cc) <= 3:
                            cc.close()
                        cc.invalidate(oid)

            temps=self._temps
            if temps:
                t=[]
                for cc in temps:
                    if rc(cc) > 3:
                        if cc is not connection and cc._version==version:
                            cc.invalidate(oid)
                        t.append(cc)
                    else: cc.close()
                self._temps=t
        finally: self._r()

    def invalidateMany(self, oids=None, version=''):
        if oids is None: self.invalidate(None, version=version)
        else:
            for oid in oids: self.invalidate(oid, version=version)

    def objectCount(self): return len(self._storage)
        
    def open(self, version='', transaction=None, temporary=0, force=None,
             waitflag=1):
        """Return a object space (AKA connection) to work in

        The optional version argument can be used to specify that a
        version connection is desired.

        The optional transaction argument can be provided to cause the
        connection to be automatically closed when a transaction is
        terminated.  In addition, connections per transaction are
        reused, if possible.

        Note that the connection pool is managed as a stack, to increate the
        likelihood that the connection's stack will include useful objects.
        """
        if type(version) is not StringType:
            raise POSException.Unimplemented, 'temporary versions'
        
        self._a()
        try:

            if transaction is not None:
                connections=transaction._connections
                if connections:
                    if connection.has_key(version) and not temporary:
                        return connections[version]
                else:
                    transaction._connections=connections={}
                transaction=transaction._connections
                    

            if temporary:
                # This is a temporary connection.
                # We won't bother with the pools.  This will be
                # a one-use connection.
                c=Connection(
                    version=version,
                    cache_size=self._version_cache_size,
                    cache_deactivate_after=
                    self._version_cache_deactivate_after)
                c._setDB(self)
                self._temps.append(c)
                if transaction is not None: transaction[id(c)]=c
                return c


            pools,pooll=self._pools
            if pools.has_key(version):
                pool, allocated, pool_lock = pools[version]
            else:
                pool, allocated, pool_lock = pools[version] = (
                    [], [], allocate_lock())
                pooll.append((pool, allocated))
                pool_lock.acquire()


            if not pool:
                c=None
                if version:
                    if self._version_pool_size > len(allocated) or force:
                        c=Connection(
                            version=version,
                            cache_size=self._version_cache_size,
                            cache_deactivate_after=
                            self._version_cache_deactivate_after)
                        allocated.append(c)
                        pool.append(c)
                elif self._pool_size > len(allocated) or force:
                    c=Connection(
                        version=version,
                        cache_size=self._cache_size,
                        cache_deactivate_after=
                        self._cache_deactivate_after)
                    allocated.append(c)
                    pool.append(c)
                    
                if c is None:
                    if waitflag:
                        self._r()
                        pool_lock.acquire()
                        self._a()
                    else: return

            elif len(pool)==1:
                # Taking last one, lock the pool
                # We know that the pool lock is not set.
                pool_lock.acquire()

            c=pool[-1]
            del pool[-1]
            c._setDB(self)
            for pool, allocated in pooll:
                for cc in pool:
                    cc._incrgc()

            if transaction is not None: transaction[version]=c
            return c

        finally: self._r()
        
    def pack(self, t):
        self._storage.pack(t,referencesf)
                           
    def setCacheDeactivateAfter(self, v): self._cache_deactivate_after=v
    def setCacheSize(self, v): self._cache_size=v

    def setClassFactory(self, factory):
        self._classFactory=factory

    def setPoolSize(self, v): self._pool_size=v
    def setVersionCacheDeactivateAfter(self, v):
        self._version_cache_deactivate_after=v
    def setVersionCacheSize(self, v): self._version_cache_size=v
    def setVersionPoolSize(self, v): self._version_pool_size=v

    def cacheStatistics(self): return () # :(

    def versionEmpty(self, version):
        return self._storage.versionEmpty(version)

class CommitVersion:
    """An object that will see to version commit

    in cooperation with a transaction manager.
    """
    def __init__(self, db, version, dest=''):
        self._db=db
        s=db._storage
        self._version=version
        self._dest=dest
        self.tpc_abort=s.tpc_abort
        self.tpc_begin=s.tpc_begin
        self.tpc_finish=s.tpc_finish
        get_transaction().register(self)

    def abort(self, reallyme, t): pass

    def commit(self, reallyme, t):
        db=self._db
        dest=self._dest
        for oid in db._storage.commitVersion(self._version, dest, t):
            db.invalidate(oid, version=dest)
    
class AbortVersion(CommitVersion):
    """An object that will see to version abortion

    in cooperation with a transaction manager.
    """

    def commit(self, reallyme, t):
        db=self._db
        version=self._version
        for oid in db._storage.abortVersion(version, t):
            db.invalidate(oid, version=version)