[SPARK-6007][SQL] Add numRows param in DataFrame.show()

[jackylk]

It is useful to let the user decide the number of rows to show in DataFrame.show

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Test build #27950 has started for PR 4767 at commit 981be52.

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[rxin]

this won't work in Java. you need to overload show to provide two shows.

[jackylk]

I added a test case in Java, it seems working. Is there any problem?

[rxin]

did you try just calling show?

[jackylk]

I tried

     DataFrame df = context.table("testData");
     df.show(10);
     df.show(1000);
     df.select("*").show(30);

Is that what you mean?

[rxin]

can you try df.show()?

in either case, I wouldn't not want to rely on Scala's generated code for default param values for bytecode level binary compatibility. Please implement two show methods, one with an int param and one without. Thanks.

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Test build #27978 has started for PR 4767 at commit d7acc18.

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[SparkQA]

Test build #27983 has started for PR 4767 at commit bb54537.

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[rxin]

what I mean is...

   /**
    * 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
    * @group basic
    */
  def show(numRows: Int): Unit = println(showString(numRows))

  /**
   * Displays the top 20 rows of the [[DataFrame]] in a tabular form.
   */
  def show(): Unit = show(20)

[rxin]

i.e don't include "for java compatibility" in the user facing doc, and don't include the default param value.

[jackylk]

Thanks a lot

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Test build #27978 has finished for PR 4767 at commit d7acc18.

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Test build #27986 has started for PR 4767 at commit 7cdbe91.

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Test build #27983 has finished for PR 4767 at commit bb54537.

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[rxin]

one more thing. can you add one more docstring test to test n = 1?

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Test build #27986 has finished for PR 4767 at commit 7cdbe91.

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[SparkQA]

Test build #28003 has started for PR 4767 at commit a0e0f4b.

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Test build #28003 has finished for PR 4767 at commit a0e0f4b.

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[rxin]

Thanks. I've merged this.