关于B+tree (附python 模拟代码)
#!/usr/bin/env pythonfrom random import randint,choice
from bisect import bisect_right,bisect_left
from collections import deque
class InitError(Exception):
pass
class ParaError(Exception):
pass
class KeyValue(object):
__slots__=('key','value')
def __init__(self,key,value):
self.key=key
self.value=value
def __str__(self):
return str((self.key,self.value))
def __cmp__(self,key):
if self.key>key:
return 1
elif self.key==key:
return 0
else:
return -1
class Bptree_InterNode(object):
def __init__(self,M):
if not isinstance(M,int):
raise InitError,'M must be int'
if M<=3:
raise InitError,'M must be greater then 3'
else:
self.__M=M
self.clist=[]
self.ilist=[]
self.par=None
def isleaf(self):
return False
def isfull(self):
return len(self.ilist)>=self.M-1
def isempty(self):
return len(self.ilist)<=(self.M+1)/2-1
@property
def M(self):
return self.__M
class Bptree_Leaf(object):
def __init__(self,L):
if not isinstance(L,int):
raise InitError,'L must be int'
else:
self.__L=L
self.vlist=[]
self.bro=None
self.par=None
def isleaf(self):
return True
def isfull(self):
return len(self.vlist)>self.L
def isempty(self):
return len(self.vlist)<=(self.L+1)/2
@property
def L(self):
return self.__L
class Bptree(object):
def __init__(self,M,L):
if L>M:
raise InitError,'L must be less or equal then M'
else:
self.__M=M
self.__L=L
self.__root=Bptree_Leaf(L)
self.__leaf=self.__root
@property
def M(self):
return self.__M
@property
def L(self):
return self.__L
def insert(self,key_value):
node=self.__root
def split_node(n1):
mid=self.M/2
newnode=Bptree_InterNode(self.M)
newnode.ilist=n1.ilist
newnode.clist=n1.clist
newnode.par=n1.par
for c in newnode.clist:
c.par=newnode
if n1.par is None:
newroot=Bptree_InterNode(self.M)
newroot.ilist=]
newroot.clist=
n1.par=newnode.par=newroot
self.__root=newroot
else:
i=n1.par.clist.index(n1)
n1.par.ilist.insert(i,n1.ilist)
n1.par.clist.insert(i+1,newnode)
n1.ilist=n1.ilist[:mid-1]
n1.clist=n1.clist[:mid]
return n1.par
def split_leaf(n2):
mid=(self.L+1)/2
newleaf=Bptree_Leaf(self.L)
newleaf.vlist=n2.vlist
if n2.par==None:
newroot=Bptree_InterNode(self.M)
newroot.ilist=.key]
newroot.clist=
n2.par=newleaf.par=newroot
self.__root=newroot
else:
i=n2.par.clist.index(n2)
n2.par.ilist.insert(i,n2.vlist.key)
n2.par.clist.insert(i+1,newleaf)
newleaf.par=n2.par
n2.vlist=n2.vlist[:mid]
n2.bro=newleaf
def insert_node(n):
if not n.isleaf():
if n.isfull():
insert_node(split_node(n))
else:
p=bisect_right(n.ilist,key_value)
insert_node(n.clist)
else:
p=bisect_right(n.vlist,key_value)
n.vlist.insert(p,key_value)
if n.isfull():
split_leaf(n)
else:
return
insert_node(node)
def search(self,mi=None,ma=None):
result=[]
node=self.__root
leaf=self.__leaf
if mi is None and ma is None:
raise ParaError,'you need to setup searching range'
elif mi is not None and ma is not None and mi>ma:
raise ParaError,'upper bound must be greater or equal than lower bound'
def search_key(n,k):
if n.isleaf():
p=bisect_left(n.vlist,k)
return (p,n)
else:
p=bisect_right(n.ilist,k)
return search_key(n.clist,k)
if mi is None:
while True:
for kv in leaf.vlist:
if kv<=ma:
result.append(kv)
else:
return result
if leaf.bro==None:
return result
else:
leaf=leaf.bro
elif ma is None:
index,leaf=search_key(node,mi)
result.extend(leaf.vlist)
while True:
if leaf.bro==None:
return result
else:
leaf=leaf.bro
result.extend(leaf.vlist)
else:
if mi==ma:
i,l=search_key(node,mi)
try:
if l.vlist==mi:
result.append(l.vlist)
return result
else:
return result
except IndexError:
return result
else:
i1,l1=search_key(node,mi)
i2,l2=search_key(node,ma)
if l1 is l2:
if i1==i2:
return result
else:
result.extend(l.vlist)
return result
else:
result.extend(l1.vlist)
l=l1
while True:
if l.bro==l2:
result.extend(l2.vlist[:i2+1])
return result
else:
result.extend(l.bro.vlist)
l=l.bro
def traversal(self):
result=[]
l=self.__leaf
while True:
result.extend(l.vlist)
if l.bro==None:
return result
else:
l=l.bro
def show(self):
print 'this b+tree is:\n'
q=deque()
h=0
q.append()
while True:
try:
w,hei=q.popleft()
except IndexError:
return
else:
if not w.isleaf():
print w.ilist,'the>
if hei==h:
h+=1
q.extend([ for i in w.clist])
else:
print ,'the leaf is,',hei
def delete(self,key_value):
def merge(n,i):
if n.clist.isleaf():
n.clist.vlist=n.clist.vlist+n.clist.vlist
n.clist.bro=n.clist.bro
else:
n.clist.ilist=n.clist.ilist+]+n.clist.ilist
n.clist.clist=n.clist.clist+n.clist.clist
n.clist.remove(n.clist)
n.ilist.remove(n.ilist)
if n.ilist==[]:
n.clist.par=None
self.__root=n.clist
del n
return self.__root
else:
return n
def tran_l2r(n,i):
if not n.clist.isleaf():
n.clist.clist.insert(0,n.clist.clist[-1])
n.clist.clist[-1].par=n.clist
n.clist.ilist.insert(0,n.ilist)
n.ilist=n.clist.ilist[-1]
n.clist.clist.pop()
n.clist.ilist.pop()
else:
n.clist.vlist.insert(0,n.clist.vlist[-1])
n.clist.vlist.pop()
n.ilist=n.clist.vlist.key
def tran_r2l(n,i):
if not n.clist.isleaf():
n.clist.clist.append(n.clist.clist)
n.clist.clist.par=n.clist
n.clist.ilist.append(n.ilist)
n.ilist=n.clist.ilist
n.clist.clist.remove(n.clist.clist)
n.clist.ilist.remove(n.clist.ilist)
else:
n.clist.vlist.append(n.clist.vlist)
n.clist.vlist.remove(n.clist.vlist)
n.ilist=n.clist.vlist.key
def del_node(n,kv):
if not n.isleaf():
p=bisect_right(n.ilist,kv)
if p==len(n.ilist):
if not n.clist.isempty():
return del_node(n.clist,kv)
elif not n.clist.isempty():
tran_l2r(n,p-1)
return del_node(n.clist,kv)
else:
return del_node(merge(n,p),kv)
else:
if not n.clist.isempty():
return del_node(n.clist,kv)
elif not n.clist.isempty():
tran_r2l(n,p)
return del_node(n.clist,kv)
else:
return del_node(merge(n,p),kv)
else:
p=bisect_left(n.vlist,kv)
try:
pp=n.vlist
except IndexError:
return -1
else:
if pp!=kv:
return -1
else:
n.vlist.remove(kv)
return 0
del_node(self.__root,key_value)
def test():
mini=2
maxi=60
testlist=[]
for i in range(1,10):
key=i
value=i
testlist.append(KeyValue(key,value))
mybptree=Bptree(4,4)
for kv in testlist:
mybptree.insert(kv)
mybptree.delete(testlist)
mybptree.show()
print '\nkey of this b+tree is \n'
if __name__=='__main__':
test()
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