[Pytables-users] my indexes go poof

[damon f. <dam...@ya...>]

Hi,

I'm having some trouble generating an index on a Table
column.  Actually, I think the index is created, but I
can't access it the next time I open the file.

I have a job which creates a very simple pytables
file.  Just one group with 4 pretty simple tables.  I
dump a bunch of data into the tables.  There is one
column on which I will usually select, so I would like
to create an index on this column.  In order to get
experience with pytables, I've done two runs over the
same input data.  In the first run I did not index any
columns.  In the second run I indexed the column of
interest.  I'm certain the index was generated because
a) I created the IsDescription class with indexed=1
for that column (very straightforward), b) that was
the only difference between the scripts for the two
runs and the output file for the indexed run was about
20% larger than the output file with no index.

When I access data (in a later Python session), using
the where operator to select on the indexed column,
the access is pretty slow, and in fact, it is SLOWER
when I run using the file with the index.  I'm pretty
sure that the index is in the file (because the file
is bigger) but it is not seen when I open the file. 
If I print the file (by typing the symbol returned by
openFile()) none of the columns are indicated as
having been indexed.  Yet, if I print the file during
the session in which it was originally created, the
column which I asked to be indexed is indeed indicated
as so.

I reproduced the error in an interactive session with
a simpler file structure.  I have attached the screen
dump of that session as 'pytables.indextest.session'. 
I've added a few annotations to this file, but it
should be pretty easy to see the problem.  I've
attached another file, 'pytables.install.session'
which is a screendump of the session where I built
installed and tested pytables.  From there you can see
the details of my configuration.  I think everything
is in order. 

So, a lot of words, but a single question.  What
happened to my index...and how can I make it not
happend?

Thanks!
  Damon

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