On Fri, 28 Oct 2005 00:17:54 +0800, "Neville C. Dempsey" <[EMAIL PROTECTED]>
wrote:
>Why does this python program fail to read record "6000000"?
>
>#!/usr/bin/env python
>import bsddb # twiceopen.py
>
>key="6000000"
>btf=bsddb.db.DB_INIT_THREAD
>
>list1=bsddb.btopen("twiceopen.tbl",btflags=btf)
>list1[key]="we have the technology"
>
>list2=bsddb.btopen("twiceopen.tbl",btflags=btf)
>#print "key:",key,"val:",list2[key] # doesn't work...
>print "first:",list2.first() # also fails first time...
>
>list1.close()
>list2.close()
>
>Maybe the solution needs one of:
> db.DB_CREATE|db.DB_INIT_MPOOL|db.DB_THREAD|db.DB_INIT_CDB
You really want to use transactions if you are going to access a database
concurrently. So that means DB_INIT_TXN. Now since you need transactions, you
need an environment, so you want to let bsddb create whatever environment files
it needs. So that means DB_CREATE. Now since there's an environment, every
process but the first to open it needs to *join* it, rather than opening it in
the usual way. So that means DB_JOINENV for all but the first open call.
Except I don't think btopen() supports half these operations. You really want
to use bsddb.db.DBEnv and bsddb.DB. Or a library that wraps them more
sensibly:
<http://divmod.org/users/viewcvs.twistd/trunk/atop/store.py?rev=9302&view=markup>.
You probably don't want everything there, but the DatabaseEnvironment class
(and supporting code) should be useful.
Jp
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