[development] Database schema abstraction and *reflection*(was: Referential integrity -- finally?)

[FGM]

Barry,

You're indeed correct in evaluating the change and understanding the
question: this was necessary because of the stringent FB limitations on the
width of indexes, and is an example where a given DBMS cannot be used to
port Drupal "as such" without an actual DB abstraction (instead of a DB API
abstraction as we have currently).

The hook_schema_alter is interesting/perplexing, BTW. I wonder where this
could take us.

More generally, as you say, such ports would need the specific module to be
patched, instead of having a function implementing the change in the DB
indendence layer, which looks like a Bad Thing. But since we're not (yet ?)
considering DML abstraction, I'm not sure we can go much further... except
(maybe) by some very clever hook_db_rewrite_sql implementations. (very ?).

Frederic.



----- Original Message ----- 
From: "Barry Jaspan" <barry at jaspan.org>
To: <development at drupal.org>
Sent: Friday, January 26, 2007 8:03 PM
Subject: Re: [development] Database schema abstraction and *reflection*(was:
Referential integrity -- finally?)


>
> "FGM" <fgm at osinet.fr> writes:
[...]
> What I see in your diagram is that you took the
> realm column out of node_access into its own table, keyed by a realm
> id.  It looks to me like this is just normalizing the node_access
> table.  Am I correct?
[...]

> I'm not sure I understand your question, but I think you are asking:
> Could this abstraction allow the Drupal-Firebird driver to convert the
> current node_access table into the separate node_access and
> node_access_realm tables as shown in your diagram?
>
> If that is the question, the answer is no.  My proposal is only for
> data-definition statements, not for abstracting data-manipulation
> statements.  Yes, one could implement the hypothetical
> hook_schema_alter (I'm making this up on the fly):
>
> function firebird_schema_alter(&$schema) {
>   unset($schema['node_access']['cols']['realm']);
>   $schema['node_access']['cols'][] = array('rid', ...);
>   $schema['node_access_realm'] = array(/* table definition goes here */);
[...]