Github user shivaram commented on a diff in the pull request:

    https://github.com/apache/spark/pull/8984#discussion_r41596831
  
    --- Diff: R/pkg/R/DataFrame.R ---
    @@ -1881,3 +1881,31 @@ setMethod("as.data.frame",
                 collect(x)
               }
     )
    +
    +#' Returns the column types of a DataFrame.
    +#' 
    +#' @name coltypes
    +#' @title Get column types of a DataFrame
    +#' @param x (DataFrame)
    +#' @return value (character) A character vector with the column types of 
the given DataFrame
    +#' @rdname coltypes
    +setMethod("coltypes",
    +          signature(x = "DataFrame"),
    +          function(x) {
    +            # TODO: This may be moved as a global parameter
    +            # These are the supported data types and how they map to
    +            # R's data types
    +            DATA_TYPES <- c("string"="character",
    +                            "double"="numeric",
    +                            "int"="integer",
    +                            "long"="integer",
    +                            "boolean"="long"
    +            )
    +
    +            # Get the data types of the DataFrame by invoking dtypes() 
function.
    +            # Some post-processing is needed.
    +            types <- as.character(t(as.data.frame(dtypes(x))[2, ]))
    +
    +            # Map Spark data types into R's data types
    +            as.character(DATA_TYPES[types])
    --- End diff --
    
    http://spark.apache.org/docs/latest/sql-programming-guide.html#data-types 
is a list that might be helpful.
    
    Also I think it might make sense to try and map them to R types and if we 
fail to find a relevant one we fallback to the SparkSQL type


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