Subject Re: Embedded Javascript
Author paulruizendaal
Hi Jim,

Trying to understand your point of view:

"Actually, I have something quite different in mind. I'm pondering a
(non-stored) procedure language in which a client can define an
arbitrarily complex set of operations to be executed on the server to
minimize round trips between the client and the server. A procedure
could be cached on a server, but wouldn't necessarily persist on the

The architecture of Nimbus allows an open ended set of protocols
between client and server, so I don't have to pick one and live with
it. At the moment, at least, I have the freedom to pick or invent a
candidate and experiment. And, since nothing that I'm aware of fits
the bill, there's room to be creative."

For the moment my mental model is of an HTTP-like protocol, or even
HTTP itself. The client would do a POST, with the actual set of
operations in its body and the reply would carry the result in some
encoding (also open ended, like MIME types).

I'm not sure how you envision the potential caching. I assume you
match a post body with a response. For this to work the procedures
must be deterministic or set a non-cacheable flag for the result. You
may want to read up on this part of HTTP, although having written
some web servers yourself you probably are already familiar with the

If the procedure language relies on caching to be efficient, chances
are that high scalability is shot, due to cache invalidation issues.
Or will you accept replies with potentially stale data?

"The basic requirements for the language are that it computationally
complete (call, branch, loop, throw/catch, etc.) and support some
notion of object that can be used to return complex results to the
client. Bootstrapping off a generally accepted language is a plus.
Running in a defensible sandbox is an absolute requirement.

I'm looking for a server side solution. The original idea of Java, for
example, was thin client applets. They didn't pan out, but Java turned
out to be a dandy server technology. Java is excellent for embedding
application level semantics into a database server, but as a vehicle
for expressing more or less ad hoc client requests, leaves a great
deal to be desired."

I think what you are trying to phrase is that you need a language
that is good at expressing the manipulation of record sets. As so
much these days is in the line of C++/Java the discussion tends to be
object collections and manipulation thereof. Perhaps this is too
narrow a view. Perhaps there is value in looking at concepts in other
language families.
- 'relational': PSQL, PL/SQL and alike offer primitives to operate on
record sets, mostly one record at a time, but sometimes record sets
at a time (eg. PL/SQL collections). You could consider to generalise
these. Perhaps (an enhanced) GDML has another life in it.
- 'array oriented': you could look to APL or J for inspiration, or
look at Lua, which uses a table as its core datatype (objects are
implemented as specialisations of tables).

"Take the DBT2/TPCC benchmark, for example. Yes, it could be coded in
Java and installed on the client. A more convenient alternative that
didn't require DBA privilege to install but still capable of
expressing a full transaction as a single client/server exchange
would be even nicer."

Agree. Note that doing a full transaction for each request is needed
if you wan to be RESTful, and that a solution needs to be found for
long running user transactions ('starting to edit a record before
lunch, finalising it after lunch'). One would need a first
transaction to read the record, and then a second to do the update.
It would be nice if the language offered some no sweat "check no
concurrent update since the read" feature.

"What I'm considering is extended JavaScript for SQL access (probably
a hundred ways to do this). The client would pass a JavaScript
request (or the name of a predefined JavaScript object) to the
server, the server would execute the given procedure, and return
whatever the procedure returned to the list. The return might be an
object, a string or number, or list of records and values, a number
of lists of records and value, correlated or serial, or whatever."

As I understand your question, you are looking for a language system
that (i) easily queries a database (in SQL, from your earlier posts),
(ii) has the ability to concisely manipulate component queries into
results, and (iii) can communicate the final result in an easily
objectifyable format, for example json or xml or whatever. Correct?

"JavaScript is a little loosey-goosey on types for my taste, all
numerics as doubles doesn't please me, but otherwise looks
interesting. I've never seen an ad hoc database stored procedure that
I've like. Heavy duty server side stuff is better in Java, but Java
is a tad heavy for the application."

I guess that this requirement relates to highly lightweight
instantiation of procedure execution, in order not to be dependent on
caching and hence kill high scalability. From this perspective Lua
may be your best shot, especially as the compilation into bytecode
can happen on the client or on the web/app server (the compiler is
only some 35kB). It has a proven JIT compiler into x86 native as well
(also weighing in at some 35kB).

"Any other interesting suggestions?"

Perhaps not interesting, but I've been looking at doing a custom
language for SQLite similar to what you seem to be looking at. The
interesting thing is that there is quite a bit of similarity between
the Lua VM and the SQLite VM (I guess you met Richard Hipp whilst you
and Ann were at the OpenSQL camp last month).

The thing that I cannot yet resolve is how to enable easy MVC style
development without using elaborate frameworks. The other toughy is
how to keep the app developer learning curve short. Something
JavaScript-like has a big plus there, as any web app developer will
be familiar with it.

The problem with JavaScript (and Lua and ...) is that when used in an
OO way, every property/method access becomes a (hash)lookup, rather
than an indexation and that slows everything down. You can compile
around that (eg. Google's V8), but then you lose the lightweight
thing. Or we simply dump the OO mindset.

I guess the only correct solution for all these issues is 42 :^)