most efficient method of storing records held in array

most efficient method of storing records held in array

[tonyg]

I have several fairly long arrays of records that I want to store to disk on a as needed basis, but I don't want to use a database.

Especially after reading that comparison between database speed and persistant objects that was recently floated.

I did look at the persistent objects library  in the Dmitrys Kazakov components library but I'm finding it difficult to understand what is going on there despite the large amount of documentation.

Are there any other examples out there using this library? I was thinking of a generic library using direct io to save on the index whenever the values are changed.

What do you guys think?

Re: most efficient method of storing records held in array

[Jeffrey Carter]

On 03/23/2015 04:56 AM, tonyg wrote:
> 
> 
> Are there any other examples out there using this library? I was thinking of
> a generic library using direct io to save on the index whenever the values
> are changed.

I think efficiency is a poor reason to avoid a simple solution, at least until
you have tried it and found it doesn't meet your timing requirements.

However, it sounds as if, for your case, the simplest solution might be to hide
the array in a package and provide Put and Get operations, with Put writing the
new value to disk using Ada.Direct_IO.

-- 
Jeff Carter
"What's the amount of the insult?"
Never Give a Sucker an Even Break
104

Re: most efficient method of storing records held in array

[Dmitry A. Kazakov]

On Mon, 23 Mar 2015 04:56:40 -0700 (PDT), tonyg wrote:

> I have several fairly long arrays of records that I want to store to disk
> on a as needed basis, but I don't want to use a database.
> 
> Especially after reading that comparison between database speed and
> persistant objects that was recently floated.
> 
> I did look at the persistent objects library  in the Dmitrys Kazakov
> components library but I'm finding it difficult to understand what is
> going on there despite the large amount of documentation.
> 
> Are there any other examples out there using this library? I was thinking
> of a generic library using direct io to save on the index whenever the
> values are changed.

The implementation of the persistence layer is based on Direct_IO,
actually.
 
> What do you guys think?

Everything depends on the intended usage. Whether data are immutable, how
frequent in relation are insertion, seek, deletion, whether elements have
fixed or variable size, should access be task-safe, which operations are
required to be atomic, should the persistent structure survive hard system
crashes, should the container file keep several structures, how they are
identified (catalogue etc), could the structures be removed independently
and so on. There is no ultimate solution and efficiency (defined in any of
multiple possible ways) highly depends on the choices made.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

Re: most efficient method of storing records held in array

[tonyg]

Thanks for the info Guys!

Thats seems a nice easy and safe way Jeff.