Parse,inspect and extract data.table from fst file

A tookit of APIs for reading fst file as data.table, could select by column, row and conditional filtering.

parse_fst(path)

slice_fst(ft, row_no)

select_fst(ft, ...)

filter_fst(ft, ...)

summary_fst(ft)

Arguments

path

path to fst file

ft

An object of class fst_table, returned by parse_fst

row_no

An integer vector (Positive)

...

The filter conditions

Value

parse_fst returns a fst_table class.

select_fst and filter_fst returns a data.table.

Details

summary_fst could provide some basic information about the fst table.

See also

fst, metadata_fst

Examples

if (FALSE) { # \dontrun{
  fst::write_fst(iris,"iris_test.fst")
  # parse the file but not reading it
  parse_fst("iris_test.fst") -> ft
  ft

  class(ft)
  lapply(ft,class)
  names(ft)
  dim(ft)
  summary_fst(ft)

  # get the data by query
  ft %>% slice_fst(1:3)
  ft %>% slice_fst(c(1,3))

  ft %>% select_fst(Sepal.Length)
  ft %>% select_fst(Sepal.Length,Sepal.Width)
  ft %>% select_fst("Sepal.Length")
  ft %>% select_fst(1:3)
  ft %>% select_fst(1,3)
  ft %>% select_fst("Se")
  ft %>% select_fst("nothing")
  ft %>% select_fst("Se|Sp")
  ft %>% select_fst(cols = names(iris)[2:3])

  ft %>% filter_fst(Sepal.Width > 3)
  ft %>% filter_fst(Sepal.Length > 6 , Species == "virginica")
  ft %>% filter_fst(Sepal.Length > 6 & Species == "virginica" & Sepal.Width < 3)

  unlink("iris_test.fst")
} # }