[DRILL-3988] Create a sys.functions table to expose available Drill functions

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.15.0
• Component/s: Metadata
• Labels: doc-complete
• Assignee: Kunal Khatua
• Reporter: Jacques Nadeau
• Reviewer: Arina Ielchiieva
• Created: 28/Oct/15 01:08
• Updated: 10/Dec/18 23:15
• Resolved: 12/Oct/18 10:19

Description

Create a new sys.functions table that returns a list of all available functions.

Key considerations:

• one row per name or one per argument set. I'm inclined to latter so people can use queries to get to data.
• we need to create a delineation between user functions and internal functions and only show user functions. 'CastInt' isn't something the user should be able to see (or run).
• should we add a description annotation that could be included in the sys.functions table?

Issue Links

• is broken by: DRILL-6762 Dynamic UDFs registered on one Drillbit are not visible on other Drillbits
• is duplicated by: DRILL-1124 Expose the list of functions (including udf/udaf) in another system or metadata table (including signature)
• is required by: DRILL-6084 Expose list of Drill functions for consumption by JavaScript libraries
• relates to: DRILL-6684 Swap sys.options and sys.options_val tables
• links to: GitHub Pull Request #1483