Re: Scheme is too complicated

[Per Bothner <bothner@cygnus.com>]

hjstein@bfr.co.il (Harvey J. Stein) writes:

| One interface I'm familiar with is the one which makes an underlying
| database file look like an associative array (aka hash table).

Sascha Ziemann <szi@aibon.ping.de> wrote:
> Consider a SQL query which returns more data than your computer has
> memory. I don't think that you will find a useful implementation that
> let's the result look like a hash table.

You missed the point.  "Looks like a hastable" does not imply that
it be implemented as an in-memory hashtable, only that it has a
similar programming interface.  (Notice also that Harvey talked
about the "underlying database file" and you talk about result
sets.)

The more important point is that an SQL table does *not*
look like hash table:  A table may have multiple keys,
can be retrieved in different search orders, and may have
various secondary indexes.  You can of course gain access
to all the records using a mapper and a filtering predicate;
the problem is you really want to translate the Scheme filter
predicate into SQL, so the database engine can do the right
optimizations and select the best indexes.  Doing that is
an interesting implementation challenge!

	--Per Bothner
Cygnus Solutions     bothner@cygnus.com     http://www.cygnus.com/~bothner