[racket] About DB and events

From: Ryan Culpepper (ryan at cs.utah.edu)
Date: Fri Feb 24 17:08:21 EST 2012

I don't think it's possible to do this strictly on the Racket side. Your 
best bet is to see if you can write a PostgreSQL procedure that 
blocks/sleeps until rows are available (or until it hits some timeout) 
and then returns them. PostgreSQL has pg_sleep, LISTEN, NOTIFY, and 
LOCK---some combination of those might be able to express what you want. 
I suggest asking on the PostgreSQL mailing list about that part. On the 
Racket side you just run the query that executes the wait-for-results 


On 02/24/2012 06:43 AM, Eduardo Bellani wrote:
> Hash: SHA1
> Hello list.
> I am building a deamon here that pings a postgres database to send
> some messages. A bit like the following code:
> (let check-loop
>      ([unsent-messages (get-unsent-messages)]) ;; get messages from DB
>    (for-each (? (message) (do-it! message)) unsent-messages)
>    (sleep *interval*)
>    (check-loop (get-unsent-messages)))
> I'm thinking this would be a great task for an event, but I'm having
> some trouble transforming a DB call into an event. Is it possible?
> Feasible? Anyone can think of alternatives? That looping and sleeping
> does not sound like a nice way to code this.
> Thanks.
> - --
> Eduardo Bellani
> fear is an alarm, not a compass.
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