Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!seismo!mcvax!cernvax!ethz!marti
From: marti@ethz.UUCP (Robert Marti)
Newsgroups: comp.databases
Subject: Re: Call Interfaces to RDBMSs
Message-ID: <174@bernina.UUCP>
Date: Sat, 8-Aug-87 05:10:39 EDT
Article-I.D.: bernina.174
Posted: Sat Aug  8 05:10:39 1987
Date-Received: Sun, 9-Aug-87 13:30:06 EDT
References: <168@bernina.UUCP> <3209@zen.berkeley.edu>
Organization: ETH Zuerich, Switzerland
Lines: 48

In article <3209@zen.berkeley.edu>, larry@xanadu.uucp (Larry Rowe) writes
in response to my previous posting:
> ...   the preprocessor that
> you mention just translates from a ``user friendly'' notation
> to an ``ugly'' subroutine call interface.   ...

Well, I don't think of EXEC SQL or ## markers as user-friendly, but
I guess that's just a matter of taste.  Speaking of a user-friendly
interface from an application program to a DBMS:  I really liked
the idea of database programming languages such as Pascal/R, Plain,
and Rigel.  Unfortunately -- as we have experienced ourselves with
Modula/R -- it is a pain to port these languages to other architectures,
operating systems, and/or database systems.

> ...
> this solution assumes that the subroutine call interface can be
> linked into your program.  on the vax and 68K/unix this is possible
> because all languages use a standard subroutine call interface.  i don't
> recall what machine you are using or what modula compiler you are
> using, but this might present a problem.   ...

We are using Sun-3s running UNIX (SunOS Release 3.2, to be exact) and
Sun Modula-2, Release 2.0.  There are two ways to call C functions:
- writing a DEFINITION MODULE FOR C whose implementation just happens
  to be a bunch of C functions
- using the SYSTEM.CCALL procedure to directly call C functions.
  The first parameter to CCALL must be an ARRAY OF CHAR which contains
  the name of the C function. The rest of the parameters are unchecked.
  CCALL may either be used as procedure or as function procedure
  returning an INTEGER.


The responses I got so far indicate that EMPRESS/32 and Sybase support
call interfaces, so I'll look into it.  On a final note, one drawback
of call interfaces occurred to me after sending out my previous message:
Most modern systems using the pre-compilation approach generate an
optimized access-plan in this step.  Unfortunately, I don't see an easy
way to this with a call interface, so it looks as if each query (call)
will have to incur the overhead of parsing the query, optimizing it
and generating an access plan.  It seems the best one could do is
generating all access plans when starting up the application.

Bob
-- 
Robert Marti                    Phone:       +41 1 256 52 36
Institut fur Informatik
ETH Zentrum/SOT                 CSNET/ARPA:  marti%ifi.ethz.ch@relay.cs.net
CH-8092 Zurich, Switzerland     UUCP:        ...seismo!mcvax!ethz!marti