Vertica and R quickie – group_concat transform function

[This article was first published on My contRibution » R, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.

I’m guessing you can do this in C++, but hey… it works for me.

You’ll notice 3 functions that need to be created, the main function which will be called from Vertica, the params functions which is optional and holds the config of parameters optionally pased to the function. And finally, and mandatory, is the factory function which tells Vertica what to expect when running ‘group_concat’.

 

 

group_concat <- function(x,y) {

 options(useFancyQuotes=FALSE)

 # initialize parameters
 sep <- ifelse(is.null(y[['delimiter']]),',',as.character(y[['delimiter']]))
 if(is.null(y[['quote']])) y[['quote']] <- 0
 doQuote <- ifelse(y[['quote']]==1 ,TRUE,FALSE) 

 if(doQuote) ret <- paste0(sQuote(x[,1]),collapse=sep)
 else ret <- paste0(x[,1],collapse=sep)

 ret

}

group_concat_params <- function() {
 params <- data.frame(datatype=c("varchar", "int"), length=c(100,NA), scale=rep(NA,2),name=c("delimiter","quote"))
 params
}

group_concat_factory <- function() {
 list(
 name=group_concat
 ,udxtype=c("transform")
 ,intype=c("any")
 ,outtype=c("varchar(65000)")
 ,parametertypecallback=group_concat_params
 # ,volatility=c("stable")
 # ,strict=c("called_on_null_input")
 )
}

After distributiong the file into the same directory on all nodes.

In Vertica run :

 

create or replace library r_func as '.../group_concat.r' language 'R';
create or replace transform function group_concat as name 'group_concat_factory' library r_func;

select group_concat(id using parameters delimiter='|', quote=1) over() from sometable;

 

 


To leave a comment for the author, please follow the link and comment on their blog: My contRibution » R.

R-bloggers.com offers daily e-mail updates about R news and tutorials about learning R and many other topics. Click here if you're looking to post or find an R/data-science job.
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.

Never miss an update!
Subscribe to R-bloggers to receive
e-mails with the latest R posts.
(You will not see this message again.)

Click here to close (This popup will not appear again)