By using making the connection from browser to server an RPC model I
have mapped the interface to the database instead of trying to map the
database to the Javascript objects. That also minimizes the network
traffic. My application server design has a criterion that network
traffic should be minimized. It is a great way to increase effective
bandwidth.
The generated HTML/Javascript pages have no redundancy and are
compressed if they are above a threshold size. The RPC between the
browser and the server uses sparse messages and not a great deal of
redundancy. It also minimizes the extent of execution of the slow,
interpreted Javascript by partitioning as much basic housekeeping to the
more efficient server side processing.
The server holds each database open as exclusive and shares it between
users and multiple user connections, minimizing database open and close
actions, keeping local cacheing and avoiding file locking.
Currently I am dreaming up ways of implementing the Javascript function
level in Sqlite. Creating the JS VM when the DB opens and having one VM
per open DB instance seems to be a way of avoiding contentions and
getting fairly efficient execution and a reasonable route for an initial
prototype. Garbage collection should take care of stale objects. I can
store user defined functions as text items in a dedicated table defining
aggregate and scalar functions in a database. A syntax directed editor
linked to JSLint and RCS can maintain syntactically correct code with
version control.
Javascript would not be a good way to implement simple functions in
Sqlite, the current custome function interface to native code is far
prefereable for that but it is appropriate for implementing larger
functions and one which require frequent user alterations.
Michael Ruck wrote:
How do you treat objects containing other objects? JS has the capabilities
to build powerful object models with hashes etc. Objects, such as these
don't map nicely to the relational model.
I'm going a different way - I'm using static HTML, which requests JSON from
the server and uses this to update the UI on the client side. However
mapping JSON to SQL is still somewhat of an issue. I've tackled it by
including metadata in JSON, but that's not very clean and I'm not really
happy with it (yet.)
Mike
-----Ursprüngliche Nachricht-----
Von: John Stanton [mailto:[EMAIL PROTECTED]
Gesendet: Freitag, 6. April 2007 18:22
An: sqlite-users@sqlite.org
Betreff: Re: AW: [sqlite] Function Language
Thankyou for the thoughtful comments. It strikes me that a JS object and an
Sqlite row map nicely. When I was writing the part of my application server
which encapsulates Sqlite rows in JSON I was struck by how simple the
interface was, particularly compared to XML which involves a little more
attention to create well formed XML and a whole lot more involvement to
parse and generate on the client side. Adding JSON as an alternative to XML
was a good idea.
I do not try to create dynamic HTML pages using JS and use a much simpler
and more efficent application specific language compiled to byte code
(somewhat analogous to Java or VDBE bytecode). At that level JS is merged
into the page in such a way that the JS is matched to the browser and locale
to remove redundancy.
The sophistication in the otherwise simple application specific language is
an inference engine to resolve a knowledge base of rules stored in the
Sqlite database and an event driven capability linked to the activity of the
database.
The same capability which creates dynamic HTML/Javascript will also generate
PostScript to deliver PDF and no doubt other formats which may show up in
the future.
Michael Ruck wrote:
I am all for it and am very interested in your project as I'm working
on something similar. I've been using JS to create dynamic HTML pages
in combination with SQLite using a JSON wrapper from this list. The
only issue I see here is the treatment of JS objects - there's again
the OO and relation mismatch involved. You may need some kind of OO
mapper to map to SQLite tables/views.
HTH,
Mike
-----Ursprüngliche Nachricht-----
Von: John Stanton [mailto:[EMAIL PROTECTED]
Gesendet: Freitag, 6. April 2007 02:43
An: sqlite-users@sqlite.org
Betreff: [sqlite] Function Language
I have been looking around at handy way to implement elaborate
functions in Sqlite. Implementing PL/SQL came to mind but recently it
struck me that Javascript has data rules very similar to Sqlite and
has the useful property that all executables are just data.
Does anyone have views for or against Javascript as an embedded
language for realizing functions? I see as a positive its data typing
affinity with Sqlite and its widespread usage and a large base of active
programmers.
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