Symptoms
Assume that you run R scripts that use the RxLocalParallel compute context or the doParallel R package. When you use sp_execute_external_script to run scripts which are written in R, you notice that the query may hang while running the parallel functions.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Resolution
This issue is fixed in the following cumulative update for SQL Server:
About cumulative updates for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:
Workaround
To work around the issue without updating, you can include some additional R code at the top of your script in sp_execute_external_script. The code is as follows:
parallel <- getNamespace("parallel")
unlockBinding("makePSOCKcluster", parallel)
internalMakePSOCKcluster <- parallel::makePSOCKcluster
wrapperMakePSOCKcluster = function(...) {
args <- list(...)
if (!("outfile" %in% names(args)) || is.null(args[["outfile"]]))
{
args[["outfile"]] <- tempfile()
}
do.call(internalMakePSOCKcluster, args)
}
parallel$makePSOCKcluster <- wrapperMakePSOCKcluster
lockBinding("makePSOCKcluster", parallel)
References
Learn about the terminology that Microsoft uses to describe software updates.
