RE: Closing a database

From: Wijck, Bart van <"Wijck,>
Date: Thu, 8 Jul 2004 13:53:56 +0200

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Content-type: text/plain

Rene,

Wow, quick response.

So it's apparently just a question of redundancy.

Agreed that you would want to export as little as needed, although it's only
2 pretty self evident pointers. Now I only export the table pointer but then
have quite a number of
         db := <SybsytemModule>.rt.base;
statements. Also a bit redundant.

Thanks, Bart




-----Original Message-----
From: René A. Krywult [mailto:rene.krywult{([at]})nowhere.xy
Sent: Thursday, July 08, 2004 1:37 PM
To: Wijck, Bart van
Cc: 'blackbox{([at]})nowhere.xy
Subject: Re: Closing a database


As I see it, you would not want to export more than is necessary. You would
not want to export any redundant (=unnecessary) information.

An interface is more clear, the less elements it contains. Everything that
is not necessary to be visible, should be opaque.

Further, what is the benefit of having the db variable globally? Is manual
deconstruction a benefit? Is it a benefit to have to manually deconstruct
the table AND the database?

Rene

=============René A. Krywult
-------------------------------------------------
"Gûrberen," pent i naneth dî,
"mabapadan a ce darach sí!"
___________________________________



----- Original von: "Wijck, Bart van" <Bart.van.Wijck{([at]})nowhere.xy

> Hi BlackBox people,

Can anyone answer the following question:

As long as you are processing a database with SQL you need database and
table objects. When you are done processing you set these object pointers to
NIL. With the explicit command Kernel.Cleanup the garbage collector closes
the database, or I presume this happens anyway when you are finish executing
altogether. The point obviously is not to keep the database open longer than
necessary.

What I do not understand why BlackBox advises to make the database pointer a
local variable and only export the table pointer. Yes you can at anytime
recreate the database pointer form the table pointer via:

        db := <sybsytem>.rt.base; (* where rt is the result table
pointer *)

But what is the big difference? The presumably large chunk of memory where
the database object is allocated is retained in any case until all (!)
references to it are set to NIL. So even if db is local and presumably set
to NIL automatically when the procedure in which it is defined has finished
executing, there's still the reference to it in rt.base (which is global and
exported).
Closing the database still needs to be done explicitly by setting rt := NIL.

So why not export both objects and set them to NIL when needed?

Regards, Bart

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Received on Thu Jul 08 2004 - 13:53:56 UTC