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

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

    [ https://issues.apache.org/jira/browse/CALCITE-2959?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16805023#comment-16805023 ] 

Ruben Quesada Lopez edited comment on CALCITE-2959 at 3/29/19 2:27 PM:
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Thanks for the feedback.
Just to give a "full" example, the EnhancedScan operator that I'm talking about would allow us to do even more complicated things, like for example:
{code}
SELECT p.name, p.address.city, p.address.street FROM Person p ORDER BY p.address.city ASC, p.address.street DESC
{code}

which would translate in something like
{code}
EnhancedScan(table=Person, sort=$2.city ASC, $2.street DESC)  // --> Collation  [2.2 ASC, 2.0 DESC]?
{code}

so the query would not have a comparison operator at composite field level, but instead individual comparison operators as composite's inner fields level.


was (Author: rubenql):
Thanks for the feedback.
Just to give a "full" example, the EnhancedScan operator that I'm talking about would allow us to do even more complicated things, like for example:
{code}
SELECT p.name, p.address.city, p.address.street FROM Person p ORDER BY p.address.city ASC, p.address.street DESC
{code}

which would translate in something like
{code}
EnhancedScan(table=Person, sort=$2.city ASC, $2.street DESC)  // --> Collation  [2.2 ASC, 2.0 DESC]?
{code}

> 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
>            Priority: Major
>
> 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.



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