[SPARK-12115][SPARKR] Change numPartitions() to getNumPartitions() to be consistent with Scala/Python

Change ```numPartitions()``` to ```getNumPartitions()``` to be consistent with Scala/Python.
<del>Note: If we can not catch up with 1.6 release, it will be breaking change for 1.7 that we also need to explain in release note.<del>

cc sun-rui felixcheung shivaram

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #10123 from yanboliang/spark-12115.

4 files changed, 45 insertions, 30 deletions

diff --git a/R/pkg/R/RDD.R b/R/pkg/R/RDD.R
index 47945c2825..00c40c38ca 100644
--- a/R/pkg/R/RDD.R
+++ b/R/pkg/R/RDD.R
@@ -306,17 +306,28 @@ setMethod("checkpoint",
 #'\dontrun{
 #' sc <- sparkR.init()
 #' rdd <- parallelize(sc, 1:10, 2L)
-#' numPartitions(rdd)  # 2L
+#' getNumPartitions(rdd)  # 2L
 #'}
-#' @rdname numPartitions
+#' @rdname getNumPartitions
+#' @aliases getNumPartitions,RDD-method
+#' @noRd
+setMethod("getNumPartitions",
+          signature(x = "RDD"),
+          function(x) {
+            callJMethod(getJRDD(x), "getNumPartitions")
+          })
+
+#' Gets the number of partitions of an RDD, the same as getNumPartitions.
+#' But this function has been deprecated, please use getNumPartitions.
+#'
+#' @rdname getNumPartitions
 #' @aliases numPartitions,RDD-method
 #' @noRd
 setMethod("numPartitions",
           signature(x = "RDD"),
           function(x) {
-            jrdd <- getJRDD(x)
-            partitions <- callJMethod(jrdd, "partitions")
-            callJMethod(partitions, "size")
+            .Deprecated("getNumPartitions")
+            getNumPartitions(x)
           })
 
 #' Collect elements of an RDD
@@ -443,7 +454,7 @@ setMethod("countByValue",
           signature(x = "RDD"),
           function(x) {
             ones <- lapply(x, function(item) { list(item, 1L) })
-            collect(reduceByKey(ones, `+`, numPartitions(x)))
+            collect(reduceByKey(ones, `+`, getNumPartitions(x)))
           })
 
 #' Apply a function to all elements
@@ -759,7 +770,7 @@ setMethod("take",
             resList <- list()
             index <- -1
             jrdd <- getJRDD(x)
-            numPartitions <- numPartitions(x)
+            numPartitions <- getNumPartitions(x)
             serializedModeRDD <- getSerializedMode(x)
 
             # TODO(shivaram): Collect more than one partition based on size
@@ -823,7 +834,7 @@ setMethod("first",
 #' @noRd
 setMethod("distinct",
           signature(x = "RDD"),
-          function(x, numPartitions = SparkR:::numPartitions(x)) {
+          function(x, numPartitions = SparkR:::getNumPartitions(x)) {
             identical.mapped <- lapply(x, function(x) { list(x, NULL) })
             reduced <- reduceByKey(identical.mapped,
                                    function(x, y) { x },
@@ -993,8 +1004,8 @@ setMethod("keyBy",
 #'\dontrun{
 #' sc <- sparkR.init()
 #' rdd <- parallelize(sc, list(1, 2, 3, 4, 5, 6, 7), 4L)
-#' numPartitions(rdd)                   # 4
-#' numPartitions(repartition(rdd, 2L))  # 2
+#' getNumPartitions(rdd)                   # 4
+#' getNumPartitions(repartition(rdd, 2L))  # 2
 #'}
 #' @rdname repartition
 #' @aliases repartition,RDD
@@ -1014,8 +1025,8 @@ setMethod("repartition",
 #'\dontrun{
 #' sc <- sparkR.init()
 #' rdd <- parallelize(sc, list(1, 2, 3, 4, 5), 3L)
-#' numPartitions(rdd)               # 3
-#' numPartitions(coalesce(rdd, 1L)) # 1
+#' getNumPartitions(rdd)               # 3
+#' getNumPartitions(coalesce(rdd, 1L)) # 1
 #'}
 #' @rdname coalesce
 #' @aliases coalesce,RDD
@@ -1024,7 +1035,7 @@ setMethod("coalesce",
            signature(x = "RDD", numPartitions = "numeric"),
            function(x, numPartitions, shuffle = FALSE) {
              numPartitions <- numToInt(numPartitions)
-             if (shuffle || numPartitions > SparkR:::numPartitions(x)) {
+             if (shuffle || numPartitions > SparkR:::getNumPartitions(x)) {
                func <- function(partIndex, part) {
                  set.seed(partIndex)  # partIndex as seed
                  start <- as.integer(base::sample(numPartitions, 1) - 1)
@@ -1112,7 +1123,7 @@ setMethod("saveAsTextFile",
 #' @noRd
 setMethod("sortBy",
           signature(x = "RDD", func = "function"),
-          function(x, func, ascending = TRUE, numPartitions = SparkR:::numPartitions(x)) {
+          function(x, func, ascending = TRUE, numPartitions = SparkR:::getNumPartitions(x)) {
             values(sortByKey(keyBy(x, func), ascending, numPartitions))
           })
 
@@ -1144,7 +1155,7 @@ takeOrderedElem <- function(x, num, ascending = TRUE) {
   resList <- list()
   index <- -1
   jrdd <- getJRDD(newRdd)
-  numPartitions <- numPartitions(newRdd)
+  numPartitions <- getNumPartitions(newRdd)
   serializedModeRDD <- getSerializedMode(newRdd)
 
   while (TRUE) {
@@ -1368,7 +1379,7 @@ setMethod("setName",
 setMethod("zipWithUniqueId",
           signature(x = "RDD"),
           function(x) {
-            n <- numPartitions(x)
+            n <- getNumPartitions(x)
 
             partitionFunc <- function(partIndex, part) {
               mapply(
@@ -1409,7 +1420,7 @@ setMethod("zipWithUniqueId",
 setMethod("zipWithIndex",
           signature(x = "RDD"),
           function(x) {
-            n <- numPartitions(x)
+            n <- getNumPartitions(x)
             if (n > 1) {
               nums <- collect(lapplyPartition(x,
                                               function(part) {
@@ -1521,8 +1532,8 @@ setMethod("unionRDD",
 setMethod("zipRDD",
           signature(x = "RDD", other = "RDD"),
           function(x, other) {
-            n1 <- numPartitions(x)
-            n2 <- numPartitions(other)
+            n1 <- getNumPartitions(x)
+            n2 <- getNumPartitions(other)
             if (n1 != n2) {
               stop("Can only zip RDDs which have the same number of partitions.")
             }
@@ -1588,7 +1599,7 @@ setMethod("cartesian",
 #' @noRd
 setMethod("subtract",
           signature(x = "RDD", other = "RDD"),
-          function(x, other, numPartitions = SparkR:::numPartitions(x)) {
+          function(x, other, numPartitions = SparkR:::getNumPartitions(x)) {
             mapFunction <- function(e) { list(e, NA) }
             rdd1 <- map(x, mapFunction)
             rdd2 <- map(other, mapFunction)
@@ -1620,7 +1631,7 @@ setMethod("subtract",
 #' @noRd
 setMethod("intersection",
           signature(x = "RDD", other = "RDD"),
-          function(x, other, numPartitions = SparkR:::numPartitions(x)) {
+          function(x, other, numPartitions = SparkR:::getNumPartitions(x)) {
             rdd1 <- map(x, function(v) { list(v, NA) })
             rdd2 <- map(other, function(v) { list(v, NA) })
 
@@ -1661,7 +1672,7 @@ setMethod("zipPartitions",
             if (length(rrdds) == 1) {
               return(rrdds[[1]])
             }
-            nPart <- sapply(rrdds, numPartitions)
+            nPart <- sapply(rrdds, getNumPartitions)
             if (length(unique(nPart)) != 1) {
               stop("Can only zipPartitions RDDs which have the same number of partitions.")
             }
diff --git a/R/pkg/R/generics.R b/R/pkg/R/generics.R
index acfd4841e1..29dd11f41f 100644
--- a/R/pkg/R/generics.R
+++ b/R/pkg/R/generics.R
@@ -133,7 +133,11 @@ setGeneric("sumRDD", function(x) { standardGeneric("sumRDD") })
 # @export
 setGeneric("name", function(x) { standardGeneric("name") })
 
-# @rdname numPartitions
+# @rdname getNumPartitions
+# @export
+setGeneric("getNumPartitions", function(x) { standardGeneric("getNumPartitions") })
+
+# @rdname getNumPartitions
 # @export
 setGeneric("numPartitions", function(x) { standardGeneric("numPartitions") })
 
diff --git a/R/pkg/R/pairRDD.R b/R/pkg/R/pairRDD.R
index 991bea4d20..334c11d2f8 100644
--- a/R/pkg/R/pairRDD.R
+++ b/R/pkg/R/pairRDD.R
@@ -750,7 +750,7 @@ setMethod("cogroup",
 #' @noRd
 setMethod("sortByKey",
           signature(x = "RDD"),
-          function(x, ascending = TRUE, numPartitions = SparkR:::numPartitions(x)) {
+          function(x, ascending = TRUE, numPartitions = SparkR:::getNumPartitions(x)) {
             rangeBounds <- list()
 
             if (numPartitions > 1) {
@@ -818,7 +818,7 @@ setMethod("sortByKey",
 #' @noRd
 setMethod("subtractByKey",
           signature(x = "RDD", other = "RDD"),
-          function(x, other, numPartitions = SparkR:::numPartitions(x)) {
+          function(x, other, numPartitions = SparkR:::getNumPartitions(x)) {
             filterFunction <- function(elem) {
               iters <- elem[[2]]
               (length(iters[[1]]) > 0) && (length(iters[[2]]) == 0)
diff --git a/R/pkg/inst/tests/test_rdd.R b/R/pkg/inst/tests/test_rdd.R
index 71aed2bb9d..7423b4f2be 100644
--- a/R/pkg/inst/tests/test_rdd.R
+++ b/R/pkg/inst/tests/test_rdd.R
@@ -28,8 +28,8 @@ intPairs <- list(list(1L, -1), list(2L, 100), list(2L, 1), list(1L, 200))
 intRdd <- parallelize(sc, intPairs, 2L)
 
 test_that("get number of partitions in RDD", {
-  expect_equal(numPartitions(rdd), 2)
-  expect_equal(numPartitions(intRdd), 2)
+  expect_equal(getNumPartitions(rdd), 2)
+  expect_equal(getNumPartitions(intRdd), 2)
 })
 
 test_that("first on RDD", {
@@ -304,18 +304,18 @@ test_that("repartition/coalesce on RDDs", {
 
   # repartition
   r1 <- repartition(rdd, 2)
-  expect_equal(numPartitions(r1), 2L)
+  expect_equal(getNumPartitions(r1), 2L)
   count <- length(collectPartition(r1, 0L))
   expect_true(count >= 8 && count <= 12)
 
   r2 <- repartition(rdd, 6)
-  expect_equal(numPartitions(r2), 6L)
+  expect_equal(getNumPartitions(r2), 6L)
   count <- length(collectPartition(r2, 0L))
   expect_true(count >= 0 && count <= 4)
 
   # coalesce
   r3 <- coalesce(rdd, 1)
-  expect_equal(numPartitions(r3), 1L)
+  expect_equal(getNumPartitions(r3), 1L)
   count <- length(collectPartition(r3, 0L))
   expect_equal(count, 20)
 })