[SPARK-8434][SQL]Add a "pretty" parameter to the "show" method to display long strings

Sometimes the user may want to show the complete content of cells. Now `sql("set -v").show()` displays:

![screen shot 2015-06-18 at 4 34 51 pm](https://cloud.githubusercontent.com/assets/1000778/8227339/14d3c5ea-15d9-11e5-99b9-f00b7e93beef.png)

The user needs to use something like `sql("set -v").collect().foreach(r => r.toSeq.mkString("\t"))` to show the complete content.

This PR adds a `pretty` parameter to show. If `pretty` is false, `show` won't truncate strings or align cells right.

![screen shot 2015-06-18 at 4 21 44 pm](https://cloud.githubusercontent.com/assets/1000778/8227407/b6f8dcac-15d9-11e5-8219-8079280d76fc.png)

Author: zsxwing <zsxwing@gmail.com>

Closes #6877 from zsxwing/show and squashes the following commits:

22e28e9 [zsxwing] pretty -> truncate
e582628 [zsxwing] Add pretty parameter to the show method in R
a3cd55b [zsxwing] Fix calling showString in R
923cee4 [zsxwing] Add a "pretty" parameter to show to display long strings

R/pkg/R/DataFrame.R

@@ -169,8 +169,8 @@ setMethod("isLocal",
 #'}
 setMethod("showDF",
           signature(x = "DataFrame"),
-          function(x, numRows = 20) {
-            s <- callJMethod(x@sdf, "showString", numToInt(numRows))
+          function(x, numRows = 20, truncate = TRUE) {
+            s <- callJMethod(x@sdf, "showString", numToInt(numRows), truncate)
             cat(s)
           })
 

python/pyspark/sql/dataframe.py

@@ -247,9 +247,12 @@ class DataFrame(object):
         return self._jdf.isLocal()
 
     @since(1.3)
-    def show(self, n=20):
+    def show(self, n=20, truncate=True):
         """Prints the first ``n`` rows to the console.
 
+        :param n: Number of rows to show.
+        :param truncate: Whether truncate long strings and align cells right.
+
         >>> df
         DataFrame[age: int, name: string]
         >>> df.show()
@@ -260,7 +263,7 @@ class DataFrame(object):
         |  5|  Bob|
         +---+-----+
         """
-        print(self._jdf.showString(n))
+        print(self._jdf.showString(n, truncate))
 
     def __repr__(self):
         return "DataFrame[%s]" % (", ".join("%s: %s" % c for c in self.dtypes))

sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala

@@ -169,8 +169,9 @@ class DataFrame private[sql](
   /**
    * Internal API for Python
    * @param _numRows Number of rows to show
+   * @param truncate Whether truncate long strings and align cells right
    */
-  private[sql] def showString(_numRows: Int): String = {
+  private[sql] def showString(_numRows: Int, truncate: Boolean = true): String = {
     val numRows = _numRows.max(0)
     val sb = new StringBuilder
     val takeResult = take(numRows + 1)
@@ -188,7 +189,7 @@ class DataFrame private[sql](
           case seq: Seq[_] => seq.mkString("[", ", ", "]")
           case _ => cell.toString
         }
-        if (str.length > 20) str.substring(0, 17) + "..." else str
+        if (truncate && str.length > 20) str.substring(0, 17) + "..." else str
       }: Seq[String]
     }
 
@@ -207,7 +208,11 @@ class DataFrame private[sql](
 
     // column names
     rows.head.zipWithIndex.map { case (cell, i) =>
+      if (truncate) {
         StringUtils.leftPad(cell, colWidths(i))
+      } else {
+        StringUtils.rightPad(cell, colWidths(i))
+      }
     }.addString(sb, "|", "|", "|\n")
 
     sb.append(sep)
@@ -215,7 +220,11 @@ class DataFrame private[sql](
     // data
     rows.tail.map {
       _.zipWithIndex.map { case (cell, i) =>
+        if (truncate) {
           StringUtils.leftPad(cell.toString, colWidths(i))
+        } else {
+          StringUtils.rightPad(cell.toString, colWidths(i))
+        }
       }.addString(sb, "|", "|", "|\n")
     }
 
@@ -331,7 +340,8 @@ class DataFrame private[sql](
   def isLocal: Boolean = logicalPlan.isInstanceOf[LocalRelation]
 
   /**
-   * Displays the [[DataFrame]] in a tabular form. For example:
+   * Displays the [[DataFrame]] in a tabular form. Strings more than 20 characters will be
+   * truncated, and all cells will be aligned right. For example:
    * {{{
    *   year  month AVG('Adj Close) MAX('Adj Close)
    *   1980  12    0.503218        0.595103
@@ -345,15 +355,46 @@ class DataFrame private[sql](
    * @group action
    * @since 1.3.0
    */
-  def show(numRows: Int): Unit = println(showString(numRows))
+  def show(numRows: Int): Unit = show(numRows, true)
 
   /**
-   * Displays the top 20 rows of [[DataFrame]] in a tabular form.
+   * Displays the top 20 rows of [[DataFrame]] in a tabular form. Strings more than 20 characters
+   * will be truncated, and all cells will be aligned right.
    * @group action
    * @since 1.3.0
    */
   def show(): Unit = show(20)
 
+  /**
+   * Displays the top 20 rows of [[DataFrame]] in a tabular form.
+   *
+   * @param truncate Whether truncate long strings. If true, strings more than 20 characters will
+   *              be truncated and all cells will be aligned right
+   *
+   * @group action
+   * @since 1.5.0
+   */
+  def show(truncate: Boolean): Unit = show(20, truncate)
+
+  /**
+   * Displays the [[DataFrame]] in a tabular form. For example:
+   * {{{
+   *   year  month AVG('Adj Close) MAX('Adj Close)
+   *   1980  12    0.503218        0.595103
+   *   1981  01    0.523289        0.570307
+   *   1982  02    0.436504        0.475256
+   *   1983  03    0.410516        0.442194
+   *   1984  04    0.450090        0.483521
+   * }}}
+   * @param numRows Number of rows to show
+   * @param truncate Whether truncate long strings. If true, strings more than 20 characters will
+   *              be truncated and all cells will be aligned right
+   *
+   * @group action
+   * @since 1.5.0
+   */
+  def show(numRows: Int, truncate: Boolean): Unit = println(showString(numRows, truncate))
+
   /**
    * Returns a [[DataFrameNaFunctions]] for working with missing data.
    * {{{

sql/core/src/test/scala/org/apache/spark/sql/DataFrameSuite.scala

@@ -492,6 +492,27 @@ class DataFrameSuite extends QueryTest {
     testData.select($"*").show(1000)
   }
 
+  test("showString: truncate = [true, false]") {
+    val longString = Array.fill(21)("1").mkString
+    val df = ctx.sparkContext.parallelize(Seq("1", longString)).toDF()
+    val expectedAnswerForFalse = """+---------------------+
+                                   ||_1                   |
+                                   |+---------------------+
+                                   ||1                    |
+                                   ||111111111111111111111|
+                                   |+---------------------+
+                                   |""".stripMargin
+    assert(df.showString(10, false) === expectedAnswerForFalse)
+    val expectedAnswerForTrue = """+--------------------+
+                                  ||                  _1|
+                                  |+--------------------+
+                                  ||                   1|
+                                  ||11111111111111111...|
+                                  |+--------------------+
+                                  |""".stripMargin
+    assert(df.showString(10, true) === expectedAnswerForTrue)
+  }
+
   test("showString(negative)") {
     val expectedAnswer = """+---+-----+
                            ||key|value|