[elephant-devel] Stored procedures

[Ian Eslick]

Do you mean stored between sessions, stored in-memory between uses,  
or stored on the DB to avoid sending queries back and forth?  My  
understanding is that Tthe expense of a SQL query is not so much in  
the parsing as it is in forming a query plan to execute.  The server  
stores query plans, but exposing parameters of the SQL statement via  
a procedure, so that they do not need to be fully recomputed later.

My intention is to focus on supporting high-performance in Berkeley  
DB and any native-lisp backends, but not to focus on doing stored  
procedures for the SQL backend.  (Although that would be a nice  
enhancement project for the SQL backend, at least for the SQL calls  
that emulate the BDB semantics on top of relational tables).

So my thinking is this.  A query compiler will compile a constraint  
expression into a closure if it is in a compiled code block, much  
like cl-ppcre handles compiling regex's.  That closure will contain a  
fully compiled query execution code block, based on the computed  
query plan.

(map-query fn '(query ...)) ==>
   (apply query-closure fn free-params)

A query closure is a mapping function.  You can also generate query  
closures and pass them around as first class objects, but you'll have  
to keep track of the order of any arguments that bind to free  
parameters.  I'm still working out these kinds of details.  The  
interpreter has to be completed and validated first.

Ian


On Apr 3, 2007, at 8:41 AM, Pierre THIERRY wrote:

> Recently, a discussion started in the Torque project, an ODB for Java
> that also provides persistence, about the possible use of stored
> procedures instead of building SQL requests, because for frequent  
> cheap
> operations, the overhead of parsing and executing SQL can be
> non-trivial.
>
> Do you think such DB-specific optimisations could make sense in  
> Elephant
> too?
>
> Curiously,
> Pierre
> -- 
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