[jira] [Created] (CALCITE-2959) Support collation on struct fields

["Ruben Quesada Lopez (JIRA)" <ji...@apache.org>]

Ruben Quesada Lopez created CALCITE-2959:
--------------------------------------------

             Summary: Support collation on struct fields
                 Key: CALCITE-2959
                 URL: https://issues.apache.org/jira/browse/CALCITE-2959
             Project: Calcite
          Issue Type: New Feature
            Reporter: Ruben Quesada Lopez


Currently, the class {{RelFieldCollation}} is used to define _"the ordering of one field of a RelNode whose output is to be sorted"_. This representation can hold only "simple" fields. In case of struct fields, a projection needs to be applied in order to reference the struct field as a simple one. For example, given this table:
{code}
CREATE TYPE Address AS (
  street VARCHAR(20) NOT NULL, 
  zipcode VARCHAR(20) NOT NULL,
  city VARCHAR(20) NOT NULL);

CREATE TABLE Person (
  id VARCHAR(20) NOT NULL,
  name VARCHAR(20) NOT NULL,
  address Address NOT NULL);
{code}

With a SQL query such as: "{{SELECT p.name, p.address.city FROM Person p ORDER BY p.address.city}}" the pseudo-plan generated would look like:
{code}
Sort (1)  // --> Collation: [1]
  Project (0 = $1, 1 = $2.city)
    Scan (table = Person)
{code}

However, what would happen if we had a specific Scan operator that would guarantee us that the records would be scanned already ordered by address.city? Something like:
{code}
EnhancedScan (table = Person, sort = $2.city)  --> Collation???
{code}
The collation of such an operator cannot be represented with the current Calcite capabilities (RelFieldCollation), because it would not be a "simple" field, but a struct field, i.e. we would need a new collation abstraction to represent it, e.g. [2.city] or [2.2]

I would like to open the discuss to see if / how we could find a solution to represent this case.



--
This message was sent by Atlassian JIRA
(v7.6.3#76005)