Disk-based or db-based associative array -- good or bad?

Disk-based or db-based associative array -- good or bad?

[William Park]

I just wanted to ask shell experts here.  Is disk-based associative
array a good thing to have for a shell?  That is, reading and writing
like normal in-memory array, ie
    typeset -A var
    var[aa]='bb'
    echo ${var[aa]}
except that 'aa':'bb' key:value will be written to and read from db file
(either Gdbm or Berkeley BD) on disk.

I'm sure other people have thought about this before me, and am
wondering why this hasn't appeared in Zsh or other shells.  Noteable
features are
    - data survives exit, logout, and shutdown
    - variables can be shared between shell processes
    - it's not SQL

-- 
William Park, Open Geometry Consulting, <opengeometry@yahoo.ca>
Linux solution for data management and processing. 

Re: Disk-based or db-based associative array -- good or bad?

[Peter Stephenson]

William Park wrote:
> I just wanted to ask shell experts here.  Is disk-based associative
> array a good thing to have for a shell?  That is, reading and writing
> like normal in-memory array, ie
>     typeset -A var
>     var[aa]='bb'
>     echo ${var[aa]}
> except that 'aa':'bb' key:value will be written to and read from db file
> (either Gdbm or Berkeley BD) on disk.

As an add-on module this would be a very good thing to have.  It would
fit in well with existing modules such as zsh/parameter and zsh/mapfile.

One problem at present is we don't have a way of associating a parameter
with a particular implementation.  I think something from ksh93 would do
this.  Otherwise we can define some `tie'-like syntax for typeset.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 692070


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Re: Disk-based or db-based associative array -- good or bad?

[Clint Adams]

> I'm sure other people have thought about this before me, and am
> wondering why this hasn't appeared in Zsh or other shells.  Noteable
> features are
>     - data survives exit, logout, and shutdown
>     - variables can be shared between shell processes
>     - it's not SQL

See the thread from Sep/Oct 2002 with subject 'db module'.
Starts with http://www.zsh.org/mla/workers/2002/msg01153.html

Re: Disk-based or db-based associative array -- good or bad?

[Clint Adams]

> See the thread from Sep/Oct 2002 with subject 'db module'.
> Starts with http://www.zsh.org/mla/workers/2002/msg01153.html

After skimming this myself, I find that I remember nearly none of the
discussion.  If I miraculously find some time to work on this, should I
just pursue Oliver's original suggestion (store the db handle in u.data)
or take another approach?