Victor Barua created CALCITE-6451:
-------------------------------------
Summary: Improve Nullability Derivation for Intersect and Minus
Key: CALCITE-6451
URL: https://issues.apache.org/jira/browse/CALCITE-6451
Project: Calcite
Issue Type: Improvement
Components: core
Reporter: Victor Barua
Assignee: Victor Barua
SetOp overrides `deriveRowType()` and computes the output row type to be the
least restrictive across all inputs
[here|https://github.com/apache/calcite/blob/8ab0b03326730aa2cc6b476b2cbd8f99799bdacb/core/src/main/java/org/apache/calcite/rel/core/SetOp.java#L116-L127].
So for example given
{code:java}
Input 1: (I64, I64, I64?, I64?)
Input 2: (I64, I64?, I64, I64?) {code}
where ? denotes nullable, the least restrictive output computes:
{code:java}
Output: (I64, I64?, I64?, I64?) {code}
For UNION operations, these nullabilities are accurate.
However for MINUS and INTERSECT there is room for improvement.
*MINUS* only returns rows from the first input, as such its output nullability
should always match that of its first input:
{code:java}
Output: (I64, I64, I64?, I64?) {code}
*INTERSECT* only returns rows that match across all inputs. If a column is not
nullable in any of the inputs, then it is not nullable in the output because no
rows can be emitted in which that column is null:
{code:java}
Output: (I64, I64, I64, I64?) {code}
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
