From b4e4f5a8a7e85dd8645b3c264d9ab21ed30271d2 Mon Sep 17 00:00:00 2001
From: Joe Isaacs <joe.isaacs@live.co.uk>
Date: Mon, 20 Jan 2025 20:17:43 +0000
Subject: [PATCH] Return empty conjunct list if filter is true (#2027)

---
 vortex-expr/src/forms/cnf.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/vortex-expr/src/forms/cnf.rs b/vortex-expr/src/forms/cnf.rs
index 062b779686..8f3500ed99 100644
--- a/vortex-expr/src/forms/cnf.rs
+++ b/vortex-expr/src/forms/cnf.rs
@@ -2,7 +2,7 @@ use vortex_error::VortexResult;
 
 use super::nnf::nnf;
 use crate::traversal::{Node as _, NodeVisitor, TraversalOrder};
-use crate::{BinaryExpr, ExprRef, Operator};
+use crate::{lit, BinaryExpr, ExprRef, Operator};
 
 /// Return an equivalent expression in Conjunctive Normal Form (CNF).
 ///
@@ -143,6 +143,10 @@ use crate::{BinaryExpr, ExprRef, Operator};
 /// ```
 ///
 pub fn cnf(expr: ExprRef) -> VortexResult<Vec<Vec<ExprRef>>> {
+    if expr == lit(true) {
+        // True in CNF
+        return Ok(vec![]);
+    }
     let nnf = nnf(expr)?;
 
     let mut visitor = CNFVisitor::default();