我想做的是使用我的多核机器从R并行运行这些sql请求

我在一台带有Oracle DB的Windows机器上.我正在跟着一个blog post使用doSNOW和foreach来尝试分割这些请求,这是我在stackoverflow上找到的最好的东西.

我已经能够使进程适用于非并行的％do％版本的foreach,但不是％dopar％.使用％dopar％它只返回一个空集.以下是设置表并运行查询的代码,以便您可以看到会发生什么.如果有太多的基本代码,请提前道歉.

我看了一些其他的R包,但没有看到一个明显的解决方案.另外,如果你有一个更好的方法来管理这种过程,我有兴趣听到它 – 只要记住,我是分析师,而不是一个计算机科学家.谢谢！

#Creating a cluster
library(doSNOW)
cl <- makeCluster(c("localhost","localhost"),type = "SOCK")
registerDoSNOW(cl)

#Connecting to database through RODBC
ch=odbcConnect("",pwd = "xxxxx",believeNRows=FALSE)
#Test connection
odbcGetInfo(ch)

#Creating database tables for example purposes
qryA1 <- "create table temptable(test int)" 
qryA2 <- "insert into temptable(test) values((1))" 
qryA3 <- "select * from temptable" 
qryA4 <- "drop table temptable" 
qryB1 <- "create table temptable2(test int)" 
qryB2 <- "insert into temptable2(test) values((2))" 
qryB3 <- "select * from temptable2" 
qryB4 <- "drop table temptable2"  

sqlQuery(ch,qryA1) 
sqlQuery(ch,qryA2) 
doesItWork <- sqlQuery(ch,qryA3) 
doesItWork
sqlQuery(ch,qryB1) 
sqlQuery(ch,qryB2) 
doesItWork <- sqlQuery(ch,qryB3) 
doesItWork

result = c()
output = c()
databases <- list('temptable','temptable2')


#Non-parallel version of foreach
system.time(
foreach(i = 1:2)%do%{
result<-sqlQuery(ch,paste('SELECT * FROM ',databases[i]))   
output[i] = result
}
) 

output

#Parallel version of foreach

outputPar = c()

system.time(
foreach(i = 1:2)%dopar%{
#Connecting to database through RODBC
ch=odbcConnect(dsn,pwd = "xxxxxx",believeNRows=FALSE)
#Test connection
odbcGetInfo(ch)
result<-sqlQuery(ch,databases[i]))   
outputPar[i] = result
}
) 

outputPar

sqlQuery(ch,qryA4)
sqlQuery(ch,qryB4)