Path: utzoo!attcan!utgpu!watmath!att!tut.cis.ohio-state.edu!brutus.cs.uiuc.edu!apple!sun-barr!cs.utexas.edu!uunet!dgis!daitc!jkrueger
From: jkrueger@daitc.daitc.mil (Jon Krueger)
Newsgroups: comp.databases
Subject: Re: Parsing Query Languages in the Client or Server
Message-ID: <631@daitc.daitc.mil>
Date: 21 Sep 89 20:58:45 GMT
References: <6155@sybase.sybase.com>
Organization: DTIC Special Projects Office (DTIC-SPO), Alexandria VA
Lines: 41

forrest@sybase.com writes:

>Assuming the client runs on a machine that supports sharable code,
>the parser can be shared among all the clients.

True, as long as all clients execute on the same machine.  This
is not the direction that most database solutions are heading.

>Parse trees might result in less network traffic than actual query text.

Both are probably small compared to network overhead.  Database
applications that spend more time communicating than computing
represent (a) poorly partitioned problems, (b) lack of power in the
data model, (c) bad database design or implementation, (d) poor
development tools, or (e) inherently large data types, e.g. images,
with respect to i/o bandwidth, or (f) one or more of the above.
The choice of form to send queries to the server has some effect,
but it's probably small.

>Detecting syntax errors in the client can prevent sending a
>syntactically incorrect query over a potentially slow network.
>It would take fewer resources to find out that a query is syntactically
>incorrect.

Fewer bottlenecked resources, perhaps.  But isn't that what the
validations, parsing, and generation logic in the front end tool
is for?  In other words, isn't this a solved problem, at least
for well behaved applications?

One advantage to using the query language is that it's a well
understood form.  You can build in correctness checks that are
not specific to a given engine, parsing strategy; you can even
build tools to check correctness for arbitrary operations on
given schema.  This property is less accessible if you use
a different intermediate form for internal communication.

-- Jon
-- 
Jonathan Krueger    jkrueger@daitc.daitc.mil   uunet!dgis!jkrueger
Isn't it interesting that the first thing you do with your
color bitmapped window system on a network is emulate an ASR33?