foreach %dopar% + RPostgreSQL

Question

I am using RPostgreSQL to connect to a local database. The setup works just fine on my Linux machine. R 2.11.1, Postgres 8.4.

I was playing with the \'foreach\' with

Answer 1

The following works and speeds up by ~ 1.5x over a sequential form. As a next step, I am wondering whether it is possible to attach a connection object to each of the workers spawned by registerDoMC. If so, then there would be no need to create/destroy the connection objects, which prevents from overwhelming the PostgreSQL server with connections.

pgparquery <- function(i) {
drv <- dbDriver("PostgreSQL"); 
con <- dbConnect(drv, dbname='nsdq'); 
lst <- eval(expr.01); #contains the SQL query which depends on 'i'
qry <- dbSendQuery(con,lst);
tmp <- fetch(qry,n=-1);
dt <- dates.qed2[i]
dbDisconnect(con);
result <- list(date=dt, idreuters=tmp$idreuters)
return(result)}

id.qed.foreach <- foreach(i = 1588:3638, .inorder=FALSE, .packages=c("DBI", "RPostgreSQL")) %dopar% {pgparquery(i)}

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Vishal Belsare