Re: [Caml-list] SQL engine in OCaml with client side cache

[Diego Olivier Fernandez Pons <dofp.ocaml@gmail.com>]

    Caml-list,

[Gerd Stolpmann wrote]
> I think this is not possible. SQL always needs access to the complete
> table for executing queries (including the complete indexes).

I am surprised by your comments. Many systems have two-layer data
storage (massive but slow one, fast but limited one), and that doesn't
affect their semantics. Consider a compiler (heap/ registers), an
operating system (swap files, RAM) or even a typical SQL database that
keeps tables in memory for fast access.

This is the same but the hard drive is on the server side, the RAM on
the client side and they communicate by Internet.

I am not saying that implementing a generic cache / swapping system
for an SQL database is easy. That's why I added that for this specific
application I can easily compute a superset of the data the user will
need. Lets take an example : say my database contains sales history
data for a convenience store chain for all stores in France, all
products for last 5 years. If my user is the Coca-Cola replenishment
manager in Paris, he only needs sales of Coca-Cola products for the
last 5 similar days for each store in Paris. Thereafter I can generate
a query on the server that sends that superset of data to the client
and let the SQL client engine work on that.

I may have underestimated the amount of work to be done, because I
thought this would be on the easier side.
My idea was the following

Server side
- 3rd part SQL database
- OCaml bindings
- Web communication interface

Client side
- SQL parser written in OCaml + interpreter
- control system to guess superset of data and request from server
- Web communication interface
- output to JavaScript widget toolkit

I was expecting to find most of the pieces already done and only
having to glue them. I was actually more afraid of the JavaScript part
than the SQL one... You can even find SQL engines written in
JavaScript out there, to run in a web browser like Jade
http://jacwright.com/489/in-memory-javascript-database/ or JOrder
(JSON) https://github.com/danstocker/jorder

At the end that's nothing but arrays and for loops.

        Diego Olivier