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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Question on bounded / unbounded strings
Date: Mon, 26 Sep 2016 09:28:23 +0200
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Date: 2016-09-26T09:28:23+02:00
List-Id: <comp.lang.ada>

On 26/09/2016 01:35, brbarkstrom@gmail.com wrote:

> I expect Dimitry wouldn't like putting Bounded_Strings into
> Direct_IO files, where they're useful for fields in records that act like
> variable length character strings in databases.

Surely not. Bounded string is a private type (A.4.4).

You *never* use such for any external activity, that would make your 
program non-portable and thus the DB too.

Therefore a text field of Direct_IO element record should always be a 
subtype of String and never bounded or unbounded string.

BTW, in many cases it is better to use Direct_IO rather as a block I/O 
medium. You never know if all application level objects would fit into a 
single block. My implementation of external B-trees keeps tree nodes in 
Direct_IO blocks with indices pointing to the blobs spread over other 
blocks arranged as a persistent memory pool. So there is no limitation 
to how large an item could be and no space loss of underfilled blocks.

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