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

[William Park <opengeometry@xxxxxxxx>]

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@xxxxxxxx>
Linux solution for data management and processing.