Design nested Index

Question

Hi,
I want to design nested Index .Is it possible or not? Is it possible to join 2 cursors that are join cursors .one example like this:
the sample record like this:
rec={'tradelead':({'offer_id':1256,'sell_buy':'s','title':'sell foods'},
{'offer_id':1257,'sell_buy':'b','title':'buy foods'},
{'offer_id':1258,'sell_buy':'s','title':'sell foods'}),
'products':({'product_id':2049,'product_name':'pressure pipes'}
,{'product_id':2050,'product_name':'pressure pipes'}
,{'product_id':2051,'product_name':'flatsheets'})}
import bsddb3
db1=bsddb3.db.DB()
class Index:
def productid(self,db2,key,data):
data1=data['products']
for Info in data1:
try:
proid=Info['product_id']
db2.put(str(proid),key)
except:
pass
def productname(self,db2,data):
data1=data['products']
for Info in data1:
try:
proid=Info['product_id']
proname=Info['product_name']
db2.put(str(proname),str(proid))
except:
pass
def offerid(self,db2,key,data):
data1=data['tradelead']
for Info in data1:
try:
offerid=Info['offer_id']
db2.put(str(offerid),key)
except:
pass
def sellbuy(self,db2,key,data):
data1=data['tradelead']
for Info in data1:
try:
offerid=Info['offer_id']
sb=Info['sell_buy']
db2.put(str(sb),str(offerid))
except:
pass
db1=bsddb3.db.DB()
db1.open("E:\\main.db",bsddb3.db.DB_BTREE,bsddb3.db.DB_CREATE)
db2=bsddb3.db.DB()
db2.set_flags(bsddb3.db.DB_DUPSORT)
db2.open("E:\\productid.db",bsddb3.db.DB_BTREE,bsddb3.db.DB_CREATE)
db3=bsddb3.db.DB()
db3.set_flags(bsddb3.db.DB_DUPSORT)
db3.open("E:\\productname.db",bsddb3.db.DB_BTREE,bsddb3.db.DB_CREATE)
db4=bsddb3.db.DB()
db4.set_flags(bsddb3.db.DB_DUPSORT)
db4.open("E:\\offerid.db",bsddb3.db.DB_BTREE,bsddb3.db.DB_CREATE)
db5=bsddb3.db.DB()
db5.set_flags(bsddb3.db.DB_DUPSORT)
db5.open("E:\\sell_buy.db",bsddb3.db.DB_BTREE,bsddb3.db.DB_CREATE)
Info=Index()
#sample code for import data
db1.put("1",str(rec))
Info.productid(db2,"1",rec)
Info.productname(db3,rec)
Info.offerid(db4,"1",rec)
Info.sellbuy(db5,"1",rec)
cur1=db3.cursor()
cur1.get("pressure pipes",bsddb3.db.DB_SET)
curlist1=[cur1]
join_cur1=db2.join(curlist1,0)
data=join_cur1.get(0)
cur2.get("s",bsddb3.db.DB_SET)
curlist2=[cur2]
join_cur2=db4.join(curlist2,0)
# Is it possible join join_curs?
curlist=[join_cur1,join_cur2]
join_cur=db1.join(curlist,0)
data=join_cur.get(0)
while data:
print data
data=join_cur.get(0)
thanks alot
regards,
saeed

Answer 1

Hi Saeed,
The join won't work if one of the cursors is a join cursor. To workaround this, you could take the keys returned by a join cursor and perform an ordinary get() or c_get() (on a normal cursor), or you may join a larger number of cursors on secondaries of a primary database. This is a normal consequence of the way join cursors are implemented in Berkeley DB. A join cursor can only retrieve the results of a join sequentially; unlike regular cursors, they're returning a result that is determined dinamically (by looking up corresponding keys in different cursors' lists), rather by pointing at entries in the database.
Regards,
Andrei