Niels Pardon created CALCITE-6877:
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Summary: Generate LogicalProject in RelRoot.project() when mapping
is not name trivial
Key: CALCITE-6877
URL: https://issues.apache.org/jira/browse/CALCITE-6877
Project: Calcite
Issue Type: Improvement
Components: core
Affects Versions: 1.38.0
Reporter: Niels Pardon
Assignee: Niels Pardon
Fix For: 1.39.0
Currently, the RelRoot.project() method only generates a project relation if
the RelRoot fields are:
* not ref trivial
* or if one of the following is not true:
** is not a DML operation
** is not a force project
** the existing top relation is not already a LogicalProject
[https://github.com/apache/calcite/blob/802fce3c41be76fca899ddb8c856d72c754d1520/core/src/main/java/org/apache/calcite/rel/RelRoot.java#L163-L169]
The result is that for a simple SQL query that selects a single field from a
table and renames the same field we are losing the renaming of the field if we
call RelRoot.project() even if we set the force parameter to true since the
relational tree embedded in the RelRoot already contains a LogicalProject at
the top of the tree.
My expectation would be that when I call RelRoot.project() that a
LogicalProject is being added also if the RelRoot fields are not name trivial
aka they are being renamed.
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