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[SPARK-18788][SPARKR] Add API for getNumPartitions #16668

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[SPARK-18788][SPARKR] Add API for getNumPartitions #16668

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34f9aa5
getNumPartitions
felixcheung Jan 21, 2017
7c057fc
rename getNumPartitions for RDD
felixcheung Jan 21, 2017
ad1bd14
fix generic
felixcheung Jan 21, 2017
bab7466
more broken calls
felixcheung Jan 22, 2017
0353978
improve
felixcheung Jan 26, 2017
c05f786
remove note
felixcheung Jan 26, 2017
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1 change: 1 addition & 0 deletions R/pkg/NAMESPACE
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Original file line number Diff line number Diff line change
Expand Up @@ -94,6 +94,7 @@ exportMethods("arrange",
"freqItems",
"gapply",
"gapplyCollect",
"getNumPartitions",
"group_by",
"groupBy",
"head",
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25 changes: 25 additions & 0 deletions R/pkg/R/DataFrame.R
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Expand Up @@ -3406,3 +3406,28 @@ setMethod("randomSplit",
}
sapply(sdfs, dataFrame)
})

#' getNumPartitions
#'
#' Return the number of partitions
#' Note: in order to compute the number of partition the SparkDataFrame has to be converted into a
#' RDD temporarily internally.
#'
#' @param x A SparkDataFrame
#' @family SparkDataFrame functions
#' @aliases getNumPartitions,SparkDataFrame-method
#' @rdname getNumPartitions
#' @name getNumPartitions
#' @export
#' @examples
#'\dontrun{
#' sparkR.session()
#' df <- createDataFrame(cars, numPartitions = 2)
#' getNumPartitions(df)
#' }
#' @note getNumPartitions since 2.1.1
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@felixcheung, should this be since 2.2.0? Just curious.

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I debated about this quite a bit - generally it should but we merged createDataFrame(..., numPartitions) to 2.1 and it felt important to have a getNumPartition in the same release too.

setMethod("getNumPartitions",
signature(x = "SparkDataFrame"),
function(x) {
getNumPartitions(toRDD(x))
})
10 changes: 5 additions & 5 deletions R/pkg/inst/tests/testthat/test_sparkSQL.R
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Expand Up @@ -196,18 +196,18 @@ test_that("create DataFrame from RDD", {
expect_equal(dtypes(df), list(c("name", "string"), c("age", "int"), c("height", "float")))
expect_equal(as.list(collect(where(df, df$name == "John"))),
list(name = "John", age = 19L, height = 176.5))
expect_equal(getNumPartitions(toRDD(df)), 1)
expect_equal(getNumPartitions(df), 1)

df <- as.DataFrame(cars, numPartitions = 2)
expect_equal(getNumPartitions(toRDD(df)), 2)
expect_equal(getNumPartitions(df), 2)
df <- createDataFrame(cars, numPartitions = 3)
expect_equal(getNumPartitions(toRDD(df)), 3)
expect_equal(getNumPartitions(df), 3)
# validate limit by num of rows
df <- createDataFrame(cars, numPartitions = 60)
expect_equal(getNumPartitions(toRDD(df)), 50)
expect_equal(getNumPartitions(df), 50)
# validate when 1 < (length(coll) / numSlices) << length(coll)
df <- createDataFrame(cars, numPartitions = 20)
expect_equal(getNumPartitions(toRDD(df)), 20)
expect_equal(getNumPartitions(df), 20)

df <- as.DataFrame(data.frame(0))
expect_is(df, "SparkDataFrame")
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