[Python-bugs-list] [ python-Bugs-584409 ] add way to detect bsddb version

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Bugs item #584409, was opened at 2002-07-21 07:29
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: paul rubin (phr)
Assigned to: Nobody/Anonymous (nobody)
Summary: add way to detect bsddb version

Initial Comment:
The bsddb module docs say that some Python
configurations use Berkeley db 1.85
and others use the incompatible 2.0.  Maybe by now
there are later versions as well.  There's no way
listed for a Python script to know which version of
bsddb is running underneath!  That's not so great,
since the versions don't interoperate and don't support
the same operations.

Proposed fix: please add a new function to the module,
bsddb.db_version().  This would
return a constant string like "1.85" or "2.0", built at
Python configuration time.


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>Comment By: paul rubin (phr)
Date: 2002-07-22 20:26

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OK, it looks like both the docs and Skip's note are a bit
unclear.  When you say only the 1.85 API is exposed, does
that mean the 1.85 file format is also used either way?  In
particular, if Python is linked with Berkeley DB 2.0 and I
create a db with it, will that db interoperate with another
application that's linked to Berkeley DB 1.85?

If it won't interoperate, then it's definitely worthwhile to
add some kind of call to the Python bsddb module to let
Python scripts find out which file format they're dealing
with.  

Also, I didn't realize only the 1.85 API was supported.  I
hope pybsddb3 can become part of the standard Python
distribution, since I'd like to use Sleepycat's transaction
features from Python scripts.

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Comment By: Skip Montanaro (montanaro)
Date: 2002-07-22 12:31

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This is an interesting idea, but one that I think is less useful than you 
might believe.  The bsddb module exposes the same API based on the 
1.85 C API regardless what version of Berkeley DB you link with.  (I 
have linked it with versions 1.85 through 4.something.)  I've been using 
the bsddb module since its inclusion in Python and have never actually 
cared what version of the underlying C API the module what linked with. 
Someone programming to the C API *would* care about version 
differences, because the C API has grown richer over the years.  The 
bsddb module code just hasn't ever used any new functionality.  Note 
that the pybsddb3 module does use the new functionality in the version 
3 and 4 APIs.

What changes on you between versions are the file formats, and you 
should only care about that at the point where you upgrade from one 
version of Berkeley DB to another.  (Generally, you realize this when you 
start getting errors trying to open old databases.)  Sleepycat provides 
command line tools to help you convert from one file version to another, 
so once you realize your file formats have changed, you wind up poking 
around your disk looking for old format Berkeley DB files, run the tools 
on them, then go back to more interesting things, like writing 
stable sorts. ;-)


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