Feature request: Routines to get meta data of the data frame without opening the whole data

[wei-wu-nyc]

I don't know if this is requested. It would be helpful to provide functions that gives back some basic info about the data frame in the save fst file without opening the whole file. For example:

1. Number of columns and rows. So that the users can determine whether to open the whole file or read part of the file.
2. May be give the name of the columns and the data type of each columns.

Thanks.

[MarcusKlik]

Hi @wei-wu-nyc , thanks for your request. The latest CRAN release of the fst package actually has a method fst.metadata which shows some basic information about a fst file in tibble-style (such as names and types). Future releases will show more information, for example the key columns and dimensions of the stored table. Hope this helps!

[wei-wu-nyc]

Thanks @MarcusKlik, this actually is enough for my current need. Did not see the fst.metadata call.

[MarcusKlik]

Using method fst.metadata from the develop branch of fst:

x = data.table(X = 1:10, B = LETTERS[1:10], key = "X")
write.fst(x, "1.fst")
fst.metadata("1.fst")

will now give you output like:

<fst file>
10 rows, 2 columns (1.fst)

* 'X': integer (key 1)
* 'B': character