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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