[SPARK-17854][SQL] rand/randn allows null/long as input seed

## What changes were proposed in this pull request?

This PR proposes `rand`/`randn` accept `null` as input in Scala/SQL and `LongType` as input in SQL. In this case, it treats the values as `0`.

So, this PR includes both changes below:
- `null` support

  It seems MySQL also accepts this.

  ``` sql
  mysql> select rand(0);
  +---------------------+
  | rand(0)             |
  +---------------------+
  | 0.15522042769493574 |
  +---------------------+
  1 row in set (0.00 sec)

  mysql> select rand(NULL);
  +---------------------+
  | rand(NULL)          |
  +---------------------+
  | 0.15522042769493574 |
  +---------------------+
  1 row in set (0.00 sec)
  ```

  and also Hive does according to [HIVE-14694](https://issues.apache.org/jira/browse/HIVE-14694)

  So the codes below:

  ``` scala
  spark.range(1).selectExpr("rand(null)").show()
  ```

  prints..

  **Before**

  ```
    Input argument to rand must be an integer literal.;; line 1 pos 0
  org.apache.spark.sql.AnalysisException: Input argument to rand must be an integer literal.;; line 1 pos 0
  at org.apache.spark.sql.catalyst.analysis.FunctionRegistry$$anonfun$5.apply(FunctionRegistry.scala:465)
  at org.apache.spark.sql.catalyst.analysis.FunctionRegistry$$anonfun$5.apply(FunctionRegistry.scala:444)
  ```

  **After**

  ```
    +-----------------------+
    |rand(CAST(NULL AS INT))|
    +-----------------------+
    |    0.13385709732307427|
    +-----------------------+
  ```
- `LongType` support in SQL.

  In addition, it make the function allows to take `LongType` consistently within Scala/SQL.

  In more details, the codes below:

  ``` scala
  spark.range(1).select(rand(1), rand(1L)).show()
  spark.range(1).selectExpr("rand(1)", "rand(1L)").show()
  ```

  prints..

  **Before**

  ```
  +------------------+------------------+
  |           rand(1)|           rand(1)|
  +------------------+------------------+
  |0.2630967864682161|0.2630967864682161|
  +------------------+------------------+

  Input argument to rand must be an integer literal.;; line 1 pos 0
  org.apache.spark.sql.AnalysisException: Input argument to rand must be an integer literal.;; line 1 pos 0
  at org.apache.spark.sql.catalyst.analysis.FunctionRegistry$$anonfun$5.apply(FunctionRegistry.scala:465)
  at
  ```

  **After**

  ```
  +------------------+------------------+
  |           rand(1)|           rand(1)|
  +------------------+------------------+
  |0.2630967864682161|0.2630967864682161|
  +------------------+------------------+

  +------------------+------------------+
  |           rand(1)|           rand(1)|
  +------------------+------------------+
  |0.2630967864682161|0.2630967864682161|
  +------------------+------------------+
  ```
## How was this patch tested?

Unit tests in `DataFrameSuite.scala` and `RandomSuite.scala`.

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #15432 from HyukjinKwon/SPARK-17854.

1 files changed, 84 insertions, 0 deletions

diff --git a/sql/core/src/test/resources/sql-tests/results/random.sql.out b/sql/core/src/test/resources/sql-tests/results/random.sql.out
new file mode 100644
index 0000000000..bca67320fe
--- /dev/null
+++ b/sql/core/src/test/resources/sql-tests/results/random.sql.out
@@ -0,0 +1,84 @@
+-- Automatically generated by SQLQueryTestSuite
+-- Number of queries: 10
+
+
+-- !query 0
+SELECT rand(0)
+-- !query 0 schema
+struct<rand(0):double>
+-- !query 0 output
+0.8446490682263027
+
+
+-- !query 1
+SELECT rand(cast(3 / 7 AS int))
+-- !query 1 schema
+struct<rand(CAST((CAST(3 AS DOUBLE) / CAST(7 AS DOUBLE)) AS INT)):double>
+-- !query 1 output
+0.8446490682263027
+
+
+-- !query 2
+SELECT rand(NULL)
+-- !query 2 schema
+struct<rand(CAST(NULL AS INT)):double>
+-- !query 2 output
+0.8446490682263027
+
+
+-- !query 3
+SELECT rand(cast(NULL AS int))
+-- !query 3 schema
+struct<rand(CAST(NULL AS INT)):double>
+-- !query 3 output
+0.8446490682263027
+
+
+-- !query 4
+SELECT rand(1.0)
+-- !query 4 schema
+struct<>
+-- !query 4 output
+org.apache.spark.sql.AnalysisException
+cannot resolve 'rand(1.0BD)' due to data type mismatch: argument 1 requires (int or bigint) type, however, '1.0BD' is of decimal(2,1) type.; line 1 pos 7
+
+
+-- !query 5
+SELECT randn(0L)
+-- !query 5 schema
+struct<randn(0):double>
+-- !query 5 output
+1.1164209726833079
+
+
+-- !query 6
+SELECT randn(cast(3 / 7 AS long))
+-- !query 6 schema
+struct<randn(CAST((CAST(3 AS DOUBLE) / CAST(7 AS DOUBLE)) AS BIGINT)):double>
+-- !query 6 output
+1.1164209726833079
+
+
+-- !query 7
+SELECT randn(NULL)
+-- !query 7 schema
+struct<randn(CAST(NULL AS INT)):double>
+-- !query 7 output
+1.1164209726833079
+
+
+-- !query 8
+SELECT randn(cast(NULL AS long))
+-- !query 8 schema
+struct<randn(CAST(NULL AS BIGINT)):double>
+-- !query 8 output
+1.1164209726833079
+
+
+-- !query 9
+SELECT rand('1')
+-- !query 9 schema
+struct<>
+-- !query 9 output
+org.apache.spark.sql.AnalysisException
+cannot resolve 'rand('1')' due to data type mismatch: argument 1 requires (int or bigint) type, however, ''1'' is of string type.; line 1 pos 7