Return columns used

Source: R/relop.R

Return columns used

columns_used(x, ..., using = NULL)

Arguments

x

rquery operation tree.
...

generic additional arguments (not used)
using

character, if not NULL set of columns used from above.

Value

vector of table qualified column names.

Examples


if (requireNamespace("DBI", quietly = TRUE) && requireNamespace("RSQLite", quietly = TRUE)) {
  my_db <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
  d1 <- rq_copy_to(my_db, 'd1',
                    data.frame(AUC = 0.6, R2 = 0.2))
  d2 <- rq_copy_to(my_db, 'd2',
                    data.frame(AUC = 0.6, D = 0.3))
  optree <- natural_join(d1, d2, by = "AUC")
  cat(format(optree))
  print(columns_used(optree))
  DBI::dbDisconnect(my_db)
}

#> mk_td("d1", c(
#>   "AUC",
#>   "R2")) %.>%
#>  natural_join(.,
#>   mk_td("d2", c(
#>     "AUC",
#>     "D")),
#>   jointype = "INNER", by = c('AUC'))
#> $d1
#> [1] "AUC" "R2" 
#> 
#> $d2
#> [1] "AUC" "D"  
#>