[ZODB-Dev] Database size increase on commit()

[tsmiller]

Tres Seaver wrote:
> 
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> tsmiller wrote:
> 
>> This is what my gut feeling was telling me.  Before I knew ANYTHING about
>> the ZODB it seemed natural and easy to just use dictionaries as data
>> structures for things such as accounts, books, dialogs, etc..   But it
>> looks
>> like the database saves the entire dictionary if anything in it changes. 
>> Is
>> this correct and is this why I need to use the PersistentMappings or
>> BTrees?
> 
> Yes, you are correct.
> 
>> Why would I use one over the other?  
> 
> Both obey the "mapping protocol" used by Python.  PersistentMapping
> tries harder to work like a dict;  the various BTee variants tend to
> scale better when the mapping gets large, at the cost of O(logN) lookup
> behavior, vs. O(1) amortizedd for the PM.
> 
> 
> 
> Tres.
> - --
> ===================================================================
> Tres Seaver          +1 540-429-0999          tseaver at palladion.com
> Palladion Software   "Excellence by Design"    http://palladion.com
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.6 (GNU/Linux)
> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
> 
> iD8DBQFHRIso+gerLs4ltQ4RAhtNAKDbG3MzQXiG5cofIjmL23o/10Z80gCeMMGX
> pRcV4PRFu7cg2Nmg1g8qSp8=
> =H4hQ
> -----END PGP SIGNATURE-----
> 
> _______________________________________________
> For more information about ZODB, see the ZODB Wiki:
> http://www.zope.org/Wikis/ZODB/
> 
> ZODB-Dev mailing list  -  ZODB-Dev at zope.org
> http://mail.zope.org/mailman/listinfo/zodb-dev
> 
> 
It is late. I am tired. I have been looking at this stuff since this
morning.  If possible, would you take a quick look at this short program and
see if you can  take a guess why it only saves the first record.  The other
two are completely ignored.  All of the records are written to memory, but
only the first comes back when I restart the program. Of course, it is
probably something obvious.  Thanks. Tom

from ZODB import FileStorage, DB
import BTrees.OOBTree

import persistent, transaction
import time
storage = FileStorage.FileStorage('books.fs')
db = DB( storage)
conn = db.open()
dbRoot = conn.root()
bTree = BTrees.OOBTree

class BookStore(persistent.Persistent):
    def __init__(self):
        if not dbRoot.has_key("books"):
            print "creating books"
            dbRoot['books'] = bTree.OOBTree()
            dbRoot['books']['1'] = {}
        
    def addBook(self, key, book):
        print "Adding a book ", key, book
        try:
            dbRoot['books']['1'][key] = book     
            transaction.commit()            
        except:
            print "transaction did not commit"

        
if __name__ == '__main__': 

    print "at the beginning"
    store, books = dbRoot['books'].iteritems().next()
##    print "store  ", store, " books ", books
    for key, book in books.items():
        print key, book
    
    bookStore = BookStore()
    bookStore.addBook('1-21', {'book-id' : "1-21", 'title':"The Red Pony"})    
    bookStore.addBook('1-20', {'book-id' : "1-24", 'title':"The Grapes of
Wrath"})
    bookStore.addBook('1-56', {'book-id' : "1-56", 'title':"Python Rules"})
    
##    print "at the end"
##    store, books = dbRoot['books'].iteritems().next()
####    print "store  ", store, " books ", books
##    for key, book in books.items():
##        print key, book
    ##print dbRoot['books'].iteritems().next() ,
type(dbRoot['books'].iteritems().next())
    db.close()


-- 
View this message in context: http://www.nabble.com/Database-size-increase-on-commit%28%29-tf4852044.html#a13888781
Sent from the Zope - ZODB-Dev mailing list archive at Nabble.com.