andygrove commented on code in PR #3796:
URL: https://github.com/apache/arrow-datafusion/pull/3796#discussion_r992505272
##########
datafusion/expr/src/logical_plan/plan.rs:
##########
@@ -1148,18 +1150,72 @@ pub struct SubqueryAlias {
#[derive(Clone)]
pub struct Filter {
/// The predicate expression, which must have Boolean type.
- pub predicate: Expr,
+ predicate: Expr,
/// The incoming logical plan
- pub input: Arc<LogicalPlan>,
+ input: Arc<LogicalPlan>,
}
impl Filter {
+ /// Create a new filter operator.
+ pub fn try_new(
+ predicate: Expr,
+ input: Arc<LogicalPlan>,
+ ) -> datafusion_common::Result<Self> {
+ // Filter predicates must return a boolean value so we try and
validate that here.
+ // Note that it is not always possible to resolve the predicate
expression during plan
+ // construction (such as with correlated subqueries) so we make a best
effort here and
+ // ignore errors resolving the expression against the schema.
+ if let Ok(predicate_type) = predicate.get_type(input.schema()) {
+ if predicate_type != DataType::Boolean {
+ return Err(DataFusionError::Plan(format!(
+ "Cannot create filter with non-boolean predicate '{}'
returning {}",
+ predicate, predicate_type
+ )));
+ }
+ }
+
+ // filter predicates should not contain aliased expressions so we
remove any aliases here
+ // but perhaps we should be failing here instead?
+ struct RemoveAliases {}
+
+ impl ExprRewriter for RemoveAliases {
+ fn mutate(&mut self, expr: Expr) ->
datafusion_common::Result<Expr> {
+ match expr {
+ Expr::Alias(expr, alias) => {
+ debug!(
+ "Attempted to create Filter predicate containing
aliased \
+ expression `{}` AS '{}'",
+ expr, alias
+ );
+ Ok(expr.as_ref().clone())
+ }
+ _ => Ok(expr.clone()),
+ }
+ }
+ }
+
+ let mut remove_aliases = RemoveAliases {};
+ let predicate = predicate.rewrite(&mut remove_aliases)?;
+
+ Ok(Self { predicate, input })
+ }
Review Comment:
This is the main point of this PR - implementing some validation when
creating a new filter operator.
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