pickleshare: hget, hset, hdict (for write efficient hash bucket file storage)

IPython/Extensions/pickleshare.py

@@ -1,267 +1,306 b''
 #!/usr/bin/env python
 
 """ PickleShare - a small 'shelve' like datastore with concurrency support
 
 Like shelve, a PickleShareDB object acts like a normal dictionary. Unlike 
 shelve, many processes can access the database simultaneously. Changing a 
 value in database is immediately visible to other processes accessing the 
 same database.
 
 Concurrency is possible because the values are stored in separate files. Hence
 the "database" is a directory where *all* files are governed by PickleShare.
 
 Example usage::
     
     from pickleshare import *
     db = PickleShareDB('~/testpickleshare')
     db.clear()
     print "Should be empty:",db.items()
     db['hello'] = 15
     db['aku ankka'] = [1,2,313]
     db['paths/are/ok/key'] = [1,(5,46)]
     print db.keys()
     del db['aku ankka']
 
 This module is certainly not ZODB, but can be used for low-load 
 (non-mission-critical) situations where tiny code size trumps the 
 advanced features of a "real" object database.
 
 Installation guide: easy_install pickleshare
 
 Author: Ville Vainio <[e-mail]>
 License: MIT open source license.
 
 """
 
 from path import path as Path
 import os,stat,time
 import cPickle as pickle
 import UserDict
 import warnings
 import glob
 
+def gethashfile(key):
+    return ("%02x" % abs(hash(key) % 256))[-2:]
+
 class PickleShareDB(UserDict.DictMixin):
     """ The main 'connection' object for PickleShare database """
     def __init__(self,root):
         """ Return a db object that will manage the specied directory"""
         self.root = Path(root).expanduser().abspath()
         if not self.root.isdir():
             self.root.makedirs()
         # cache has { 'key' : (obj, orig_mod_time) }
         self.cache = {}
 
     def __getitem__(self,key):
         """ db['key'] reading """
         fil = self.root / key
         try:
             mtime = (fil.stat()[stat.ST_MTIME])
         except OSError:
             raise KeyError(key)
 
         if fil in self.cache and mtime == self.cache[fil][1]:
             return self.cache[fil][0]
         try:
             # The cached item has expired, need to read
             obj = pickle.load(fil.open())
         except:
             raise KeyError(key)
             
         self.cache[fil] = (obj,mtime)
         return obj
     
     def __setitem__(self,key,value):
         """ db['key'] = 5 """
         fil = self.root / key
         parent = fil.parent
         if parent and not parent.isdir():
             parent.makedirs()
         pickled = pickle.dump(value,fil.open('w'))
         try:
             self.cache[fil] = (value,fil.mtime)
         except OSError,e:
             if e.errno != 2:
                 raise
     
+    def hset(self, hashroot, key, value):
+        hroot = self.root / hashroot
+        if not hroot.isdir():
+            hroot.makedirs()
+        hfile = hroot / gethashfile(key)
+        d = self.get(hfile, {})
+        d.update( {key : value})
+        self[hfile] = d                
+
+    def hget(self, hashroot, key, default = None):
+        hroot = self.root / hashroot
+        hfile = hroot / gethashfile(key)
+        d = self.get(hfile, None)
+        #print "got dict",d,"from",hfile
+        if d is None:
+            return default
+        return d.get(key, default)
+
+    def hdict(self, hashroot):
+        buckets = self.keys(hashroot + "/*")
+        hfiles = [f for f in buckets]
+        all = {}
+        for f in hfiles:
+            # print "using",f
+            all.update(self[f])
+            self.uncache(f)
+        
+        return all
+    
     def __delitem__(self,key):
         """ del db["key"] """
         fil = self.root / key
         self.cache.pop(fil,None)
         try:
             fil.remove()
         except OSError:
             # notfound and permission denied are ok - we
             # lost, the other process wins the conflict
             pass
         
     def _normalized(self, p):
         """ Make a key suitable for user's eyes """
         return str(self.root.relpathto(p)).replace('\\','/')
     
     def keys(self, globpat = None):
         """ All keys in DB, or all keys matching a glob"""
         
         if globpat is None:
             files = self.root.walkfiles()
         else:
             files = [Path(p) for p in glob.glob(self.root/globpat)]
         return [self._normalized(p) for p in files if p.isfile()]
 
     def uncache(self,*items):
         """ Removes all, or specified items from cache
         
         Use this after reading a large amount of large objects
         to free up memory, when you won't be needing the objects
         for a while.
          
         """
         if not items:
             self.cache = {}
         for it in items:
             self.cache.pop(it,None)
             
     def waitget(self,key, maxwaittime = 60 ):
         """ Wait (poll) for a key to get a value
         
         Will wait for `maxwaittime` seconds before raising a KeyError.
         The call exits normally if the `key` field in db gets a value
         within the timeout period.
         
         Use this for synchronizing different processes or for ensuring
         that an unfortunately timed "db['key'] = newvalue" operation 
         in another process (which causes all 'get' operation to cause a 
         KeyError for the duration of pickling) won't screw up your program 
         logic. 
         """
         
         wtimes = [0.2] * 3 + [0.5] * 2 + [1]
         tries = 0
         waited = 0
         while 1:
             try:
                 val = self[key]
                 return val
             except KeyError:
                 pass
             
             if waited > maxwaittime:
                 raise KeyError(key)
             
             time.sleep(wtimes[tries])
             waited+=wtimes[tries]
             if tries < len(wtimes) -1:
                 tries+=1
     
     def getlink(self,folder):
         """ Get a convenient link for accessing items  """
         return PickleShareLink(self, folder)
     
     def __repr__(self):
         return "PickleShareDB('%s')" % self.root
         
         
                 
 class PickleShareLink:
     """ A shortdand for accessing nested PickleShare data conveniently.
 
     Created through PickleShareDB.getlink(), example::
 
         lnk = db.getlink('myobjects/test')
         lnk.foo = 2
         lnk.bar = lnk.foo + 5
     
     """
     def __init__(self, db, keydir ):    
         self.__dict__.update(locals())
         
     def __getattr__(self,key):
         return self.__dict__['db'][self.__dict__['keydir']+'/' + key]
     def __setattr__(self,key,val):
         self.db[self.keydir+'/' + key] = val
     def __repr__(self):
         db = self.__dict__['db']
         keys = db.keys( self.__dict__['keydir'] +"/*")
         return "<PickleShareLink '%s': %s>" % (
             self.__dict__['keydir'],
             ";".join([Path(k).basename() for k in keys]))
             
         
 def test():
     db = PickleShareDB('~/testpickleshare')
     db.clear()
     print "Should be empty:",db.items()
     db['hello'] = 15
     db['aku ankka'] = [1,2,313]
     db['paths/nest/ok/keyname'] = [1,(5,46)]
+    db.hset('hash', 'aku', 12)
+    db.hset('hash', 'ankka', 313)
+    print "12 =",db.hget('hash','aku')
+    print "313 =",db.hget('hash','ankka')
+    print "all hashed",db.hdict('hash')
     print db.keys()
     print db.keys('paths/nest/ok/k*')
     print dict(db) # snapsot of whole db
     db.uncache() # frees memory, causes re-reads later
 
     # shorthand for accessing deeply nested files
     lnk = db.getlink('myobjects/test')
     lnk.foo = 2
     lnk.bar = lnk.foo + 5
     print lnk.bar # 7
 
 def stress():
     db = PickleShareDB('~/fsdbtest')
     import time,sys
     for i in range(1000):
-        for j in range(300):
+        for j in range(1000):
             if i % 15 == 0 and i < 200:
                 if str(j) in db:
                     del db[str(j)]
                 continue
 
             if j%33 == 0:
                 time.sleep(0.02)
             
             db[str(j)] = db.get(str(j), []) + [(i,j,"proc %d" % os.getpid())]
+            db.hset('hash',j, db.hget('hash',j,15) + 1 )
+            
         print i,
         sys.stdout.flush()
         if i % 10 == 0:
             db.uncache()
     
 def main():
     import textwrap
     usage = textwrap.dedent("""\
     pickleshare - manage PickleShare databases 
     
     Usage:
         
         pickleshare dump /path/to/db > dump.txt
         pickleshare load /path/to/db < dump.txt
         pickleshare test /path/to/db
     """)
     DB = PickleShareDB
     import sys
     if len(sys.argv) < 2:
         print usage
         return
         
     cmd = sys.argv[1]
     args = sys.argv[2:]
     if cmd == 'dump':
         if not args: args= ['.']
         db = DB(args[0])
         import pprint
         pprint.pprint(db.items())
     elif cmd == 'load':
         cont = sys.stdin.read()
         db = DB(args[0])
         data = eval(cont)
         db.clear()
         for k,v in db.items():
             db[k] = v
     elif cmd == 'testwait':
         db = DB(args[0])
         db.clear()
         print db.waitget('250')
     elif cmd == 'test':
         test()
         stress()
     
 if __name__== "__main__":
     main()
     
     
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