[DRILL-57] Add a logical operator that returns a constant result, similar to VALUES operator in SQL

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.1.0-m1
• Assignee: Jason Altekruse
• Reporter: Julian Hyde
• Due: 06/Jun/13
• Created: 29/Mar/13 07:17
• Updated: 09/Oct/13 18:09
• Resolved: 19/Jun/13 18:14

Description

Add a logical operator that returns a constant result. This is necessary to be able to create values out of thin air, if you don't know what tables exist.

This operator is analogous to the VALUES operator in SQL. For example,

VALUES (1, 'a'), (2, 'b'), (3, 'c')

returns 3 rows with 2 columns and

VALUES (1, 'a'), (2, 'b'), (3, 'c') AS t(c1, c2)

allows you to name those columns "c1" and "c2". VALUES is useful for evaluating expressions that don't belong in a table, for example

VALUES 10 + 3

(Some databases would express this "SELECT 10 + 3". Same idea, and same underlying relational operator.)

The JSON for this new operator might look like this:

{
op: "constant",
content: { [

{c1: 1, c2: "a"}

,

{c1: 2, c3: ["x", "y", "z"]}

] }
}

This operator is necessary in order to implement the SQL VALUES clause.