[SPARK-10863][SPARKR] Method coltypes() (New version)

This is a follow up on PR #8984, as the corresponding branch for such PR was damaged.

Author: Oscar D. Lara Yejas <olarayej@mail.usf.edu>

Closes #9579 from olarayej/SPARK-10863_NEW14.

R/pkg/DESCRIPTION

@@ -34,4 +34,5 @@ Collate:
     'serialize.R'
     'sparkR.R'
     'stats.R'
+    'types.R'
     'utils.R'

R/pkg/NAMESPACE

@@ -23,9 +23,11 @@ export("setJobGroup",
 exportClasses("DataFrame")
 
 exportMethods("arrange",
+              "as.data.frame",
               "attach",
               "cache",
               "collect",
+              "coltypes",
               "columns",
               "count",
               "cov",
@@ -262,6 +264,4 @@ export("structField",
        "structType",
        "structType.jobj",
        "structType.structField",
-       "print.structType")
-
-export("as.data.frame")
+       "print.structType")
\ No newline at end of file

R/pkg/R/DataFrame.R

@@ -2152,3 +2152,52 @@ setMethod("with",
             newEnv <- assignNewEnv(data)
             eval(substitute(expr), envir = newEnv, enclos = newEnv)
           })
+
+#' Returns the column types of a DataFrame.
+#' 
+#' @name coltypes
+#' @title Get column types of a DataFrame
+#' @family dataframe_funcs
+#' @param x (DataFrame)
+#' @return value (character) A character vector with the column types of the given DataFrame
+#' @rdname coltypes
+#' @examples \dontrun{
+#' irisDF <- createDataFrame(sqlContext, iris)
+#' coltypes(irisDF)
+#' }
+setMethod("coltypes",
+          signature(x = "DataFrame"),
+          function(x) {
+            # Get the data types of the DataFrame by invoking dtypes() function
+            types <- sapply(dtypes(x), function(x) {x[[2]]})
+
+            # Map Spark data types into R's data types using DATA_TYPES environment
+            rTypes <- sapply(types, USE.NAMES=F, FUN=function(x) {
+
+              # Check for primitive types
+              type <- PRIMITIVE_TYPES[[x]]
+
+              if (is.null(type)) {
+                # Check for complex types
+                for (t in names(COMPLEX_TYPES)) {
+                  if (substring(x, 1, nchar(t)) == t) {
+                    type <- COMPLEX_TYPES[[t]]
+                    break
+                  }
+                }
+
+                if (is.null(type)) {
+                  stop(paste("Unsupported data type: ", x))
+                }
+              }
+              type
+            })
+
+            # Find which types don't have mapping to R
+            naIndices <- which(is.na(rTypes))
+
+            # Assign the original scala data types to the unmatched ones
+            rTypes[naIndices] <- types[naIndices]
+
+            rTypes
+          })
\ No newline at end of file

R/pkg/R/generics.R

@@ -1047,3 +1047,7 @@ setGeneric("attach")
 #' @rdname with
 #' @export
 setGeneric("with")
+
+#' @rdname coltypes
+#' @export
+setGeneric("coltypes", function(x) { standardGeneric("coltypes") })
\ No newline at end of file

R/pkg/R/schema.R

@@ -115,20 +115,7 @@ structField.jobj <- function(x) {
 }
 
 checkType <- function(type) {
-  primtiveTypes <- c("byte",
-                     "integer",
-                     "float",
-                     "double",
-                     "numeric",
-                     "character",
-                     "string",
-                     "binary",
-                     "raw",
-                     "logical",
-                     "boolean",
-                     "timestamp",
-                     "date")
-  if (type %in% primtiveTypes) {
+  if (!is.null(PRIMITIVE_TYPES[[type]])) {
     return()
   } else {
     # Check complex types

R/pkg/R/types.R

+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# types.R. This file handles the data type mapping between Spark and R
+
+# The primitive data types, where names(PRIMITIVE_TYPES) are Scala types whereas
+# values are equivalent R types. This is stored in an environment to allow for
+# more efficient look up (environments use hashmaps).
+PRIMITIVE_TYPES <- as.environment(list(
+  "byte"="integer",
+  "tinyint"="integer",
+  "smallint"="integer",
+  "integer"="integer",
+  "bigint"="numeric",
+  "float"="numeric",
+  "double"="numeric",
+  "decimal"="numeric",
+  "string"="character",
+  "binary"="raw",
+  "boolean"="logical",
+  "timestamp"="POSIXct",
+  "date"="Date"))
+
+# The complex data types. These do not have any direct mapping to R's types.
+COMPLEX_TYPES <- list(
+  "map"=NA,
+  "array"=NA,
+  "struct"=NA)
+
+# The full list of data types.
+DATA_TYPES <- as.environment(c(as.list(PRIMITIVE_TYPES), COMPLEX_TYPES))

R/pkg/inst/tests/test_sparkSQL.R

@@ -1467,8 +1467,9 @@ test_that("SQL error message is returned from JVM", {
   expect_equal(grepl("Table not found: blah", retError), TRUE)
 })
 
+irisDF <- createDataFrame(sqlContext, iris)
+
 test_that("Method as.data.frame as a synonym for collect()", {
-  irisDF <- createDataFrame(sqlContext, iris)
   expect_equal(as.data.frame(irisDF), collect(irisDF))
   irisDF2 <- irisDF[irisDF$Species == "setosa", ]
   expect_equal(as.data.frame(irisDF2), collect(irisDF2))
@@ -1503,6 +1504,27 @@ test_that("with() on a DataFrame", {
   expect_equal(nrow(sum2), 35)
 })
 
+test_that("Method coltypes() to get R's data types of a DataFrame", {
+  expect_equal(coltypes(irisDF), c(rep("numeric", 4), "character"))
+
+  data <- data.frame(c1=c(1,2,3),
+                     c2=c(T,F,T),
+                     c3=c("2015/01/01 10:00:00", "2015/01/02 10:00:00", "2015/01/03 10:00:00"))
+
+  schema <- structType(structField("c1", "byte"),
+                       structField("c3", "boolean"),
+                       structField("c4", "timestamp"))
+
+  # Test primitive types
+  DF <- createDataFrame(sqlContext, data, schema)
+  expect_equal(coltypes(DF), c("integer", "logical", "POSIXct"))
+
+  # Test complex types
+  x <- createDataFrame(sqlContext, list(list(as.environment(
+    list("a"="b", "c"="d", "e"="f")))))
+  expect_equal(coltypes(x), "map<string,string>")
+})
+
 unlink(parquetPath)
 unlink(jsonPath)
 unlink(jsonPathNa)