[ python-Bugs-849662 ] reading shelves is really slow

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Thu Nov 27 05:32:58 EST 2003


Bugs item #849662, was opened at 2003-11-26 14:06
Message generated for change (Comment added) made by ganssauge
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=849662&group_id=5470

Category: Extension Modules
Group: Python 2.3
Status: Open
Resolution: None
Priority: 5
Submitted By: Gottfried Ganßauge (ganssauge)
Assigned to: Raymond Hettinger (rhettinger)
Summary: reading shelves is really slow

Initial Comment:
My application uses a shelve-file which is created by 
another process using the same python version.
Before python2.3 using this shelve with the exact same 
application was almost twice as fast as a binary pickle 
containing the same data.
Now with python2.3 the same application is suddenly 
about 150 times slower than using the binary pickle.

The usage is as follows:
   idx_dict = shelve.open (idx_dict_name, "r")
   ...
   while not infile.eof:
      index = get_index_from_somewhere_else()
      if not idx_dict.has_key (index):
          do_something(index)
      else:
          do_something_else(index)

   idx.dict.close()
   
Profiling revealed that most of the time is spent within 
userdict.

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>Comment By: Gottfried Ganßauge (ganssauge)
Date: 2003-11-27 10:32

Message:
Logged In: YES 
user_id=792746

I uploaded my profiling data, maybe it will help you ...
Here is the information you requested:
----------------><------------------------><------------
(gotti at gglinux 534) 
PYTHONPATH=../../../COMMON.DEVEL/Tools/python/lib.linux-
i686-2.3 python Konvertierung/entsch_pass2.py HI69228 x HR 
all_idx2.shelve <hi69228.sgml
Traceback (most recent call last):
  File "Konvertierung/entsch_pass2.py", line 1026, in ?
    init_idx_dict (idx_dict_name)
  File "../../COMMON/lib/EDB.py", line 54, in init_idx_dict
    idx_dict.has_key([])
  File "/usr/lib/python2.3/shelve.py", line 104, in has_key
    return self.dict.has_key(key)
  File "/usr/lib/python2.3/bsddb/__init__.py", line 142, in 
has_key
    return self.db.has_key(key)
TypeError: String or Integer object expected for key, list found
(gotti at gglinux 535) 
PYTHONPATH=../../../COMMON.DEVEL/Tools/python/lib.linux-
i686-2.2 python2.2 Konvertierung/entsch_pass2.py HI69228 x 
HR all_idx2.shelve <hi69228.sgml
Traceback (most recent call last):
  File "Konvertierung/entsch_pass2.py", line 1026, in ?
    init_idx_dict (idx_dict_name)
  File "../../COMMON/lib/EDB.py", line 54, in init_idx_dict
    idx_dict.has_key([])
  File "/usr/lib/python2.2/shelve.py", line 62, in has_key
    return self.dict.has_key(key)
TypeError: key type must be string
(gotti at gglinux 536) python -V
Python 2.3.2
(gotti at gglinux 537) python2.2 -V
Python 2.2.3
(gotti at gglinux 538) uname -a
Linux gglinux 2.4.22 #1 SMP Mon Nov 3 11:40:28 CET 2003 
i686 unknown unknown GNU/Linux
(gotti at gglinux 538) cat /etc/debian_version
testing/unstable
(gotti at gglinux 539) python2.2 -c 'import shelve ; d = 
shelve.open("all_idx2.shelve", "r"); print len (d.keys()) ; print 
d.keys()[0], d [d.keys()[0]]'
34983
HI568817 None
(gotti at gglinux 540)  python2.3 -c 'import shelve ; d = 
shelve.open("all_idx2.shelve", "r"); print "# items in shelve:", 
len (d.keys()) ; print "Items look like: index", d.keys()
[0], "value", d [d.keys()[0]]'
# items in shelve: 34983
Items look like: index HI568817 value None


----------------------------------------------------------------------

Comment By: Raymond Hettinger (rhettinger)
Date: 2003-11-27 09:17

Message:
Logged In: YES 
user_id=80475

I can reproduce a four-fold slowdown that persists even
after the UserDict.DictMixin lines are commented out of
shelve.py and bsddb.__init__.py.  For me, the only thing
that has changed is the underlying bsddb implementation.

Let's see if you system is going somewhere else to get its
shelving done.  After the first line, add:  idx_dict.has_key
([])
Then post the traceback here.

Do that for both Py2.2 and for Py2.3.  Thank you.

Also, post what a typical record in the index and tell me
how many entries are typically in idx_dict.  That way, I can
try to reproduce your timings with greater fidelity.

Which os are you using and what the minor bugfix verion
numbers of the Py2.2 and PY2.3 you are using.

----------------------------------------------------------------------

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