Re: [Pytables-users] Why didn't the ZODB work

[Francesc A. <fa...@op...>]

Hi,

Just to satisfy your curiosity, I've started to work with ZODB about 1 year
and half ago, and it wasn't useful to me mainly for two reasons:

- I needed to save very large amounts of data (from hundreds of MB on), and
in that time ZODB had some memory leaks, that, in the end, made my
application to crash. I've heard that they have already fixed that, but I
personally did not check that again.

- The most important reason was efficency. I needed very fast access
(basically, only limited by the I/O capabilities of the disk subsystem) to
the data that I've saved on disk, and ZODB did not cope with this. I
remember that the reason was that ZODB uses cPickle to serialize the data,
and cPickle, while it is reasonably fast, it is about 100 times slower (when
reading) than pytables (see:
http://pytables.sourceforge.net/doc/PyCon.html#section4).

But, my needs are presumably different than yours, and pytables also has its
limitations, being the most important that it can't deal with completely
general objects, as ZODB can do, but only with tables (or arrays, including
strings) of data. Besides, it does not support strings of variable length,
and you may need that in your applications. This last inconvenience can be
circumvented, though, as long as your objects fits in-memory.

PyTables also has its advantages, and an important one is that, in my
opinion, pytables is very pythonic in that it supports the "natural naming"
manner to access to your data from Python (see:
http://pytables.sourceforge.net/html-doc/usersguide-html1.html#section1.2),
which is very powerful when dealing with hierarchical structures (see also:
http://pytables.sourceforge.net/html-doc/usersguide-html3.html#section3.2).

My personal suggestion is that, if you are not going to deal with very large
amounts of data or, performance is not an issue to you, you should try first
ZODB. If it doesn't fulfill your needs, or you just happens to love "natural
naming" (as I do), then give pytables a chance.

Hope that helps,

Francesc

A Dimarts 15 Juliol 2003 18:15, Ronald L Chichester va escriure:
> I read the home page of the project, and saw that the
> author of pyTables tried the ZODB but didn't find it
> satisfactory.  Just out of sheer curiosity, why wasn't the
> ZODB satisfactory.
>
> The reason that I ask is that I'm going through the same
> problem and am looking for a solution.  In this case, I
> have a set of text clauses in a document that need to be
> viewed in a hierarchical manner for drafting, but when
> "published" have to be in a sequential manner.  Thus, the
> "publisher" has to recursively go through the hierarchy
> and number the text elements (and reference the number of
> the parent element) and insert that into the text that is
> "published".
>
> Would pyTables help me do that?
>
> Thanks in advance,
>
> Ron
>
>
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-- 
Francesc Alted