ametel01 commented on code in PR #22948:
URL: https://github.com/apache/datafusion/pull/22948#discussion_r3427199343
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datafusion/sql/src/expr/mod.rs:
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@@ -55,6 +55,99 @@ mod unary_op;
mod value;
impl<S: ContextProvider> SqlToRel<'_, S> {
+ pub(crate) fn warn_on_null_equality_predicate(&self, predicate: &SQLExpr) {
+ fn null_value_span(expr: &SQLExpr) -> Option<Span> {
+ match expr {
+ SQLExpr::Value(ValueWithSpan {
+ value: Value::Null,
+ span,
+ }) => Span::try_from_sqlparser_span(*span),
+ _ => None,
+ }
+ }
+
+ fn null_equality_warning(expr: &SQLExpr) -> Option<Diagnostic> {
+ let SQLExpr::BinaryOp { left, op, right } = expr else {
+ return None;
+ };
+
+ let (message, help) = match op {
+ BinaryOperator::Eq => (
+ "comparison with NULL using `=` always evaluates to NULL",
+ "use `IS NULL` to check for NULL values",
+ ),
+ BinaryOperator::NotEq => (
+ "comparison with NULL using `<>` always evaluates to NULL",
+ "use `IS NOT NULL` to check for non-NULL values",
+ ),
+ _ => return None,
+ };
+
+ let null_span = null_value_span(left).or_else(||
null_value_span(right));
+ null_span.map(|null_span| {
+ Diagnostic::new_warning(
+ message,
+ Span::try_from_sqlparser_span(expr.span()),
+ )
+ .with_help(help, Some(null_span))
+ })
+ }
+
Review Comment:
Fixed. NULL detection is now independent of span conversion; the warning is
emitted even when the NULL literal has no sqlparser span, with the help span
omitted in that case.
Added test_eq_null_warning_without_null_span.
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