[ZODB-Dev] Feature Request 2381 : Persistent object iterator in Storage

[Barry A. Warsaw]

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>>>>> "GW" == Greg Ward <gward@mems-exchange.org> writes:

    GW> Yes, I would like to see an official API for this too.  I'll
    GW> attach a script I wrote to walk over an entire ZODB by
    GW> incrementing OIDs.  It's more interesting than useful, but it
    GW> *is* interesting.  ;-) It won't work out-of-the-box because it
    GW> relies on our init_database(), get_connection(), and
    GW> get_database() utility routines.  Exercise for the reader,
    GW> etc. etc.

There is a (under-documented <wink>) iteration interface for storages,
which might give you what you need.  FileStorage and now Berkeley Full
storage both support this interface, and BaseStorage even has a
copyTransactionsFrom() method that will copy all transactions and
objects from a source storage into the destination storage.

FWIW, I'm using this to debug some problems with Full's pack() method.
I can create a reproducible problem with a couple of Zope actions,
then I copy its database into a virgin Full db, and can now run pack()
over the copy without destroying the evidence.

I don't think this interface is actually documented anywhere, except
in an email Jim sent to me a few weeks ago.  He slapped a ZPL on it,
so I don't see why I can't post it here <wink>.  It's in scarecrow
form.

Does this help?

-Barry


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from types import IntType, StringType, NoneType
import types
from OID import OID
from ReferencesFunction import ReferencesFunction
from Transaction import Transaction
import ZODB.POSException
from interface import Interface, Standard, Return, Either, Tuple, Standard

class TransactionsInteration(Interface.Base):
    """Transactions iteration

    Transaction iteration facilitates copying and analysing storage
    transaction data.
    """

    def iterator():
        "Get a transactions iterator for the storage"
        return Return(TransactionsIterator, "The transactions")

class TransactionsIterator(Interface.Base):
    """Provide foreward iteration through the transactions in a storage.

    Transactions *must* be accessed sequentially (e.g. with a for loop).

    Transactions returned in commit order, which is also transaction id
    (time stamp) order.
    """

    def __getitem__(i):
        """Return the ith item in the sequence of transaction data.

        Items must be accessed sequentially. An IndexError will be raised
        after all of the items have been returned."""

        return Return(RecordIterator, "Transaction data, including records")

class RecordsIterator(Interface.Base):
    """Provide transaction meta-data and foreward iteration through
    the transactions in a storage.
    
    Records *must* be accessed sequentially (e.g. with a for loop).
    """
       
    def __getitem__(i):
        "Return the ith item in the sequence of record data.

        Items must be accessed sequentially. An IndexError will be raised
        after all of the items have been returned."""

        return Return(RecordData, "Record data")
    
    tid=Interface.Attribute(
        '''Transaction id

        This is an 8-byte time-stamp string.
        ''')
    status=Interface.Attribute(
        """Transaction status code:

        ' ' -- normal

        'p' -- Transaction has been packed, ans contains incomplete data.

        Note that undone ('u') and checkpoint transactions ('c') should
        not be included.
        """)
    

    user=Interface.Attribute('Transaction user')
    description=Interface.Attribute('Transaction description')
    _extension=Interface.Attribute('Transaction meta-data disctionary')

class Record(Interface.Base):
    oid=Interface.Attribute("Object id")
    serial=Interface.Attribute("Object serial data")
    version=Interface.Attribute("Version string")
    data=Interface.Attribute("Data pickle")







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