[SPARK-26245][SQL] Add Float literal

[wangyum]

What changes were proposed in this pull request?

This PR adds parser support for Float literals.

Hive support this feature:

How was this patch tested?

unit tests

[SparkQA]

Test build #99568 has finished for PR 23199 at commit 57faa41.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[wangyum]

retest this please

[SparkQA]

Test build #99570 has finished for PR 23199 at commit 57faa41.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[wangyum]

retest this please

[SparkQA]

Test build #99574 has finished for PR 23199 at commit 57faa41.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[kiszk]

retest this please

[kiszk]

cc @maropu @gatorsmile

[gatorsmile]

Could you move the test cases to the end of the file?

Also clearly specify the positive and negative test cases in the comments?

More test cases are needed.

[gatorsmile]

Could you check who supports these Float literals? What are their restrictions?

The ANSI SQL standard does not have such a literal.

[maropu]

This is implementation-specific;

hive> create temporary table t1 as select 1.0F;
hive> describe t1;
OK
f                   	decimal(1,0)  

hive> create temporary table t2 as select 1.0D;
hive> describe t2;
OK
_c0                 	double  

postgres=# create temporary table t1 as select 1.0F;
postgres=# \d t1
 f      | numeric | 

postgres=# create temporary table t2 as select 1.0D;
postgres=# \d t2
 d      | numeric | 

mysql> create temporary table t1 as select 1.0F;
mysql> describe t1;
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| F     | decimal(2,1) | NO   |     | 0.0     | NULL  |
+-------+--------------+------+-----+---------+-------+

mysql> create temporary table t2 as select 1.0D;
mysql> describe t2;
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| D     | decimal(2,1) | NO   |     | 0.0     | NULL  |
+-------+--------------+------+-----+---------+-------+

[SparkQA]

Test build #99578 has finished for PR 23199 at commit 57faa41.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[dongjoon-hyun]

Hi, @wangyum .
In Hive 2.3, 1.0D is considered as Double, but 1.0F is considered as 1.0 F where F is an alias.
In Hive 1.2, 1.0D and 1.0F are considered as 1.0 D and 1.0 F where D and F are aliases.
So, this is not for Hive compatibility. We had better close this PR.