Thomas Rebele created CALCITE-7264:
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Summary: New API for determining if an operator may throw
Key: CALCITE-7264
URL: https://issues.apache.org/jira/browse/CALCITE-7264
Project: Calcite
Issue Type: New Feature
Reporter: Thomas Rebele
The SQL standard defines that 1/0 throws an exception. Calcite follows the
standard here. However, some projects that use Calcite (e.g., Hive) define the
result of 1/0 as NULL. This may lead to different results in RexSimplify: E.g.,
IS NULL(1/0) would throw for the SQL standard semantics, but would return TRUE
for the Hive semantics.
RexSimplify handles this with a concept called "safe" defined in
[RexSimplify#isSafeExpression|https://github.com/apache/calcite/blob/34989b0ed7793cedf713c2f159de6247a730458c/core/src/main/java/org/apache/calcite/rex/RexSimplify.java#L1631].
The safe operators are defined in
[RexSimplify.SafeRexVisitor|https://github.com/apache/calcite/blob/34989b0ed7793cedf713c2f159de6247a730458c/core/src/main/java/org/apache/calcite/rex/RexSimplify.java#L1490].
The goal of this ticket is to make the behavior configurable. We can continue
to attach the safeness to the operators, so we could move the safeOps set
somewhere else. Here some examples:
* boolean RelDataTypeSystem#canOperatorThrow(SqlKind op)
* boolean RelDataTypeSystem#canOperatorThrow(SqlOperator op)
* boolean RelDataTypeSystem#isNoExceptOperator(...) //noexcept notion borrowed
from C++
* boolean RelDataTypeSystem#isSafeOperator
* Set<SqlKind> RelDataTypeSystem#noexceptOperators()
The safeness information would be useful for other parts of the code as well,
e.g., CALCITE-5315.
See the related discussions:
*
https://issues.apache.org/jira/browse/CALCITE-7145?focusedCommentId=18016030#comment-18016030
* [http://lists.apache.org/thread/cp7h28k1yfxv421q12y1wopbwgrzdzrx]
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