[jira] [Created] (CALCITE-819) Add a "contract" for the result of a relational expression

["Julian Hyde (JIRA)" <ji...@apache.org>]

Julian Hyde created CALCITE-819:
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             Summary: Add a "contract" for the result of a relational expression
                 Key: CALCITE-819
                 URL: https://issues.apache.org/jira/browse/CALCITE-819
             Project: Calcite
          Issue Type: Bug
            Reporter: Julian Hyde
            Assignee: Julian Hyde


Add a "contract" for the result of a relational expression consisting of:
* column names (maybe not unique),
* possible multiple uses of the same column (without duplicating the column in the input relational expression),
* convention,
* column data types,
* physical representation (e.g. as List or Object[]),
* sort order.

Currently that contract is expressed by a relational expression. But all of the aspects of the contract are at odds with best practices for relational expressions elsewhere in the tree. This is why we want to represent the contract not as a relational expression.

See CALCITE-793 for an example of how a query does not ask for a sorted result, but because it is posed on a sorted table the planner assumes that the result has to be sorted. Maybe back out parts of 793's fix as part of fixing this issue.

We would probably be able to obsolete RelCollations.PRESERVE.

It is possible that the contract would bubble up as far as the Avatica signature.



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