[Catalyst] using a persistent hash in a model

[Jonathan Rockway]

On Saturday 07 July 2007 10:59:27 am Perrin Harkins wrote:
> On 7/7/07, Daniel McBrearty <danielmcbrearty at gmail.com> wrote:
> > Is there any easy way to keep some ad-hoc persistent data out of the
> > database?
>
> Sure.  Most of them are either lossy or tricky to use, and tend to be
> poor for concurrent reading/writing.
>
> The obvious options are:
> - BerkeleyDB.  Fast, but limited to one machine, and tricky to get
> right because of insufficient docs for the advanced locking features.
> Still, a good bet.

BerkeleyDB has an RPC layer for talking to remote clients.  I find the docs 
sufficient:

http://www.oracle.com/technology/documentation/berkeley-db/db/gsg/C/index.html

The C API is exactly the same as the Perl API.  (Which sucks.  But at least 
there are no surprises.)

> - Cache::FastMmap.  Fast, but lossy.  Will silently drop your data if
> you go over the limit you set.  Limited to one machine.
> - Cache::Memcached.  Fast (although much slower than BerkeleyDB or
> Cache::FastMmap), but lossy.  Silently drops data if you go over the
> limit you set.  Loses everything if the daemon is stopped for any
> reason.  Works for a cluster though.
>
> None of these have the same locking capabilities that a database does,

I don't think the word "database" implies anything about locking (or 
relations, or ACID)...

> i.e. writers block readers and there's no easy way to do pessimistic
> locking.  (I think BerkeleyDB supports pessimistic locking, but I
> can't remember for sure.)

BerkeleyDB locking is pretty flexible.  The transaction system supports all 
the isolation levels that you would expect.  Rather than worrying about 
locks, I would just pick the isolation level I need and let the DBMS figure 
it out. 

> If you already have a database, using it will be easier than getting
> any of these right.

Agreed.  Session::Store::DBIC just Storables a hash into a table.  Querying 
the individual fields is impossible, but nobody wants to do that anyway.

-- 
package JAPH;use Catalyst qw/-Debug/;($;=JAPH)->config(name => do {
$,.=reverse qw[Jonathan tsu rehton lre rekca Rockway][$_].[split //,
";$;"]->[$_].q; ;for 1..4;$,=~s;^.;;;$,});$;->setup;
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