lowka commented on code in PR #7768:
URL: https://github.com/apache/ignite-3/pull/7768#discussion_r2945718765
##########
modules/sql-engine/src/main/java/org/apache/ignite/internal/sql/engine/exec/exp/ConverterUtils.java:
##########
@@ -221,10 +221,18 @@ private static Expression convertToTimestamp(Expression
operand, RelDataType tar
methodName = "toTimestampLtzExact";
}
+ // Box primitive operand to ensure the null-safe Object overload is
selected,
+ // and RexImpTable builds a correct condition in genValueStatement()
method
+ // if type is long then the condition: is input_isNull ? 0 :
<toTimestampExact>
+ // Otherwise, when type is Long, the condition is is input_isNull ?
null : <toTimestampExact>
+ Expression safeOperand = Primitive.is(operand.getType())
Review Comment:
After some digging, I have come to the conclusion that for each CAST
X(non-nullable) -> Y(nullable) the code that performs the conversion should be
manually wrapped in `input != null ? null : <expr>`.
There are plenty of evidence to support this in `EnumUtils' `public static
Expression convert(Expression operand, Type fromType, Type toType)`
```
// else if (fromType == BigDecimal.class) {
// E.g. from "BigDecimal" to "String"
// Generate "SqlFunctions.toString(x)"
return Expressions.condition(
Expressions.equal(operand, RexImpTable.NULL_EXPR),
RexImpTable.NULL_EXPR,
Expressions.call(
SqlFunctions.class,
"toString",
operand));
}
...
// Generate "x == null ? null : UnsignedType.toULong(x)"
return Expressions.condition(
Expressions.equal(operand, RexImpTable.NULL_EXPR),
RexImpTable.NULL_EXPR,
Expressions.call(
UnsignedType.class,
functionName,
operand));
```
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