Re: Data Dictionary and Configuration Files with Guile Scheme

[Thien-Thi Nguyen <ttn@gnuvola.org>]

() Romel Sandoval <romel@lavabit.com>
() Thu, 05 Aug 2010 12:15:44 -0500

   What do you think?

I use Guile-PG (several modules) and a homegrown metainfo table
accessible via ‘(ttn-do zzz various-db) personal-pgtable-defs’ et al:
http://www.gnuvola.org/software/ttn-do/ttn-do.html.gz#zzz-various_002ddb

Here is ~/.pgtable-defs, omitting some parts:

  ;;; ~/.pgtable-defs --- database descriptions -*- scheme -*-
  
  ;; Keyword Expansions
  ;; ------------------
  
  ((#:pk "PRIMARY KEY")
   (#:u  "UNIQUE")
   (#:nn "NOT NULL")
   (#:mf "MATCH FULL")
   (#:dc "ON DELETE CASCADE")
   (#:uc "ON UPDATE CASCADE")
   (#:r  "REFERENCES")
   (#:tz "WITH TIME ZONE"))
  
  ;; Database Table Definitions
  ;; --------------------------
  ;;
  ;; ((DB-1 (TABLE DEF ...) (TABLE DEF ...) ...)
  ;;  (DB-2 (TABLE DEF ...) (TABLE DEF ...) ...) ...)
  ;;
  ;; Some day `infer-defs' will be able to round-trip these...
  
  (("ttn"
  
    ("sw_maint"
     (v    bool #:nn)
     (url  text #:nn)
     (mon  text #:nn)
     (name text #:pk)
     (orig text)
     (mtim timestamp[])))                 ; 0: mon
  
   ("gnuvola"
  
    ("updbad"
     (time     timestamp #:pk)
     (cause    text)
     (errmsg   text))
  
    ("updok"
     (time     timestamp #:pk)
     (wrote    int4)
     (read     int4)
     (rate     float4)
     (total    int4)
     (speedup  float4))
  
    ("updfiles"
     (file     text)
     (move     char)
     (time     timestamp #:r "updok" #:dc #:uc))))
  
  ;;; ~/.pgtable-defs ends here

This file consists of two forms.  The first is (hopefully)
self-explanatory.  The second describes two databases:

  db       tables
  -------  -----------------------
  ttn      sw_maint
  gnuvola  updbad, updok, updfiles

Each table's columns are further described in a way that really ought to
be queryable from the backend, so that is a Code Enhancement Opportunity
for the Guile-PG reflection module alluded to by the "Some day" comment.

Although i think SQL is ugly (and thus concur in jest, i believe,
with Andy Wingo's admonition :-), Guile-PG makes it livable.  E.g.:
http://www.gnuvola.org/software/guile-pg/qcons-notes.txt

So, to answer your question: yes, sexps work fine as a Data Dictionary.