Re: question about 3.12 Storable feature

[mikeh@minivend.com]

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Quoting Larry Leszczynski (larryl@furph.com):
> 
> Hi Mike -
> 
> Regarding new 3.12 features:
>  
> >     * Added a Storable interface selectable at software
> >       configuration time. If Storable is installed, and the
> >       file _db_storable is present in the MiniVend software root,
> >       (or the environment variable MINIVEND_STORABLE_DB is true)
> >       then Storable will be used not only for sessions but for
> >       all GDBM and DB_File storage. THIS BREAKS EXISTING CATALOGS.
>                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
> Can you clarify this?  Is it the fact that .gdbm files have already been
> created that will make things break?  For instance, if I stop my current
> 3.11 MiniVend processes, delete all the session and database .gdbm files
> so they get recreated from scratch later when I start 3.12, will this
> work?
> 

Good eye as usual, Larry.

Yes. It breaks catalogs only if there are existing .db or .gdbm files. If
you delete them all and let MV rebuild them from the source then you
are fine. But that is ALL catalogs on that MiniVend instance; you cannot
mix and match.

I should clarify this in the WHATSNEW file; but I did want it to sound
dire. I just know someone is going to be down for days as a result
of this. 8-\ But it was needed.

I forget if it was Rob Zimmerman's post or someone else's which made
me revisit the storage speed for larger record sizes. Basically, the 
original algorithm is quite competitive with Storable for small record
sizes, but for larger record sizes Storable blows MiniVend's internal
routine away. If you have a 1000-byte record you can expect read times
to improve substantially; for record sizes less than 256 bytes the gain
will be small.

One thing I forgot to add to the list; you can now use both Berkeley
DB and GDBM files in the same catalog. I will try and remember to document
this; basically, you can select any type with:

	Database products  DB_FILE  1
	Database inventory GDBM     1
	Database country   MEMORY   1

I am using this in a couple of cases; there is some evidence that 
Berkeley DB files are faster for read but not as good for write.
(For those watching at home, this does depend on having the library
built into your Perl.)

-- 
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