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From: forrest@sybase.com
Newsgroups: comp.databases
Subject: Parsing Query Languages in the Client or Server
Message-ID: <6155@sybase.sybase.com>
Date: 20 Sep 89 20:40:41 GMT
Sender: news@sybase.sybase.com
Reply-To: forrest@sybase.com
Organization: Sybase, Inc.
Lines: 33

I used to work at Britton Lee. Now I work at Sybase. At Britton Lee
query languages were parsed in the clients and parse trees were sent
to the server. Here at Sybase we send the query language to the
server to be parsed.

I'd like to hear peoples comments about the strengths and weaknesses
of both approaches. I'll start.

Assuming the client runs on a machine that supports sharable code,
the parser can be shared among all the clients. If the client runs
on a machine that doesn't support shareable code then this is a big
disadvantage since each executable and executing image must contain
the parser. Obviously, having a server do the parsing result in only
one copy of the parser even if the platform it runs on doesn't support
shareable code.

It could be argued that parsing is not data serving. If you accept
this opinion then you probably don't think that a server should
do parsing. 

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

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.

I'm sure there are many other concerns that I'm missing.

Jon Forrest
forrest@sybase.com
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415-596-3422