CODEWITHSUNDEEP
pythondatabasepython-3.xpython-3.6zodb
K.Mulier
K.Mulier

Reputation: 9650

ZODB python database with Filestorage: why do temporary files stay on the disk?

I'm experimenting with the ZODB database module in Python 3.6. In my experiment, I create a TreeSet() and fill it with data. Then I commit the transaction (which saves the changes to disk) and close the database.

from ZODB.FileStorage import FileStorage
from ZODB import DB
from persistent import Persistent
from BTrees.OOBTree import TreeSet
import transaction

if __name__ == '__main__':
    # 1. Create ZODB database
    # ------------------------
    storage = FileStorage("C:/database_test/mydb.db")
    db = DB(storage)
    conn = db.open()
    root = conn.root()
    root.files = TreeSet()


    # 2. Fill the TreeSet
    # --------------------
    ...

    # 3. Save and close
    # ------------------
    transaction.commit()
    conn.close()
    db.close() # <- is this even necessary?

I look at the files remaining on my harddrive. As you can see, there are three temporary files remaining there - even after I've closed the database.

enter image description here

Did I close something (database, connection, storage, transaction, ...) not properly?

Note:
I don't know if this is important, but my system is as follows:

Upvotes: 3

Views: 425

Answers (2)

metatoaster
metatoaster

Reputation: 18948

The .index file is not a temporary file, but it is the index file that is persisted. If absent, it will always be fully regenerated (which will take a bit of time for a larger database).

The .temp file is for transient data that is generated before being fully committed.

The .lock file is to ensure that no two process open that file. It contains the PID of the last process that opened it. If it has terminated a new process will then write its PID into it.

There are actually more files than this, and they are documented inside the class docstring.

Upvotes: 4

BoarGules
BoarGules

Reputation: 16951

No, they are not really temporary files. They are permanent files with sometimes transient data.

In addition to the data file, some ancillary files are created. These can be lost without affecting data integrity, however losing the index file may cause extremely slow startup. (http://www.zodb.org/en/latest/reference/storages.html#included-storages)

Upvotes: 1

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