[CALCITE-1921] Add DAY as Reserved Function Name, And add day() build-in scalar function

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: core
• Assignee: sunjincheng
• Reporter: sunjincheng
• Created: 03/Aug/17 02:54
• Updated: 28/Aug/17 19:54

Description

I want add `DAY()` as build-in scalar function in calcite. It's looks like as following:

DAY('2015-04-30 01:01:01.1234567') -> 30
DAYOFMONTH('2007-02-03') -> 3

What do you think julianhyde ?

• MySql: DAY() is a synonym for DAYOFMONTH().
  https://dev.mysql.com/doc/refman/5.7/en/date-and-time-functions.html#function_day

• MsSql: DAY returns the same value as DATEPART (day, date).
  https://docs.microsoft.com/en-us/sql/t-sql/functions/day-transact-sql

• Oracle: Do not support `Day()`
  http://docs.oracle.com/cd/E11882_01/server.112/e41084/functions002.htm#SQLRF51179

• SQL2003:
  http://jtc1sc32.org/doc/N2301-2350/32N2311T-text_for_ballot-CD_9075-2.pdf