bsddb btree set_location() semantics changed

[gpshead]

BPO	788421
Nosy	@gpshead

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/gpshead'
closed_at = <Date 2004-03-16.07:59:33.000>
created_at = <Date 2003-08-13.23:21:08.000>
labels = ['extension-modules']
title = 'bsddb btree set_location() semantics changed'
updated_at = <Date 2004-03-16.07:59:33.000>
user = 'https://github.com/gpshead'

bugs.python.org fields:

activity = <Date 2004-03-16.07:59:33.000>
actor = 'gregory.p.smith'
assignee = 'gregory.p.smith'
closed = True
closed_date = None
closer = None
components = ['Extension Modules']
creation = <Date 2003-08-13.23:21:08.000>
creator = 'gregory.p.smith'
dependencies = []
files = []
hgrepos = []
issue_num = 788421
keywords = []
message_count = 3.0
messages = ['17747', '17748', '17749']
nosy_count = 1.0
nosy_names = ['gregory.p.smith']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue788421'
versions = ['Python 2.3']

[gpshead]

In the old bsddb module a bsddb.btopen(..) database
would return the next available key+value on a
set_location(key) call when key did not exist in the
database. In python 2.3 (pybsddb) it raises an
exception and leaves the cursor at an unknown position
in the database.

[reported by Anthony McDonaly on comp.lang.python]

>>> import os
>>> import bsddb
>>> os.chdir('/tmp')
>>> my_data = bsddb.btopen('testing', 'c')
>>> for i in range(10):
...   if i == 5:
...     pass
...   else:
...     my_data['%d'%i] = '%d'%(i*i)
...
>>> my_data.keys()
['0', '1', '2', '3', '4', '6', '7', '8', '9']
>>> my_data.sync()
>>> my_data.set_location('5')
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File
"/space/python-2.3/lib/python2.3/bsddb/__init__.py",
line 117, in set_location
    return self.dbc.set(key)
_bsddb.DBNotFoundError: (-30991, 'DB_NOTFOUND: No
matching key/data pair found')

Correct behaviour would have been to return ('6', '36')

[gpshead]

Logged In: YES
user_id=413

Yes this is a bug. The set_location() method should have been calling set_range() rather than set() internally.

Fixing that exposed another bug: set_range() would crash when looking up a key that exists in hash or rn databases.

Both bugs have been fixed to fix this one in python 2.4 & pybsddb CVS.

This bugfix should go into python 2.3.4.

[gpshead]

Logged In: YES
user_id=413

committed fix to head and release23-maint along with an associated fix for set_range where it could free() memory that it doesn't own on non B-Tree databases.