data.table materialized join vs not

data_table_materialized_join_vs_not.R

## count

benchmark(
  nrow(d[dm, nomatch=0L, on="x"]),
  d[dm, .N, nomatch=0L, on="x"],
replications = 5, columns = c("test", "replications", "elapsed", "relative"))

#                                test replications elapsed relative
#2   d[dm, .N, nomatch = 0, on = "x"]            5  28.535    1.000
#1 nrow(d[dm, nomatch = 0, on = "x"])            5  38.562    1.351


## sum(y)

benchmark(
  sum(d[dm, nomatch=0L, on="x"]$y),
  d[dm, sum(y), nomatch=0L, on="x"],
replications = 5, columns = c("test", "replications", "elapsed", "relative"))

#                                  test replications elapsed relative
#2 d[dm, sum(y), nomatch = 0, on = "x"]            5  36.113    1.000
#1  sum(d[dm, nomatch = 0, on = "x"]$y)            5  39.207    1.086