From 1b29a3fd27f3888a477ce02c9534ef2d1f35feec Mon Sep 17 00:00:00 2001
From: Scott Donnelly <scott@donnel.ly>
Date: Thu, 4 Apr 2024 20:55:47 +0100
Subject: [PATCH] feat: add AlwaysTrue and AlwaysFalse to Predicate

---
 crates/iceberg/src/expr/predicate.rs | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/crates/iceberg/src/expr/predicate.rs b/crates/iceberg/src/expr/predicate.rs
index da8a863d29..2381630d6f 100644
--- a/crates/iceberg/src/expr/predicate.rs
+++ b/crates/iceberg/src/expr/predicate.rs
@@ -217,6 +217,10 @@ impl<T: Display + Debug> Display for SetExpression<T> {
 /// Unbound predicate expression before binding to a schema.
 #[derive(Debug, PartialEq)]
 pub enum Predicate {
+    /// AlwaysTrue predicate, for example, `TRUE`.
+    AlwaysTrue,
+    /// AlwaysFalse predicate, for example, `FALSE`.
+    AlwaysFalse,
     /// And predicate, for example, `a > 10 AND b < 20`.
     And(LogicalExpression<Predicate, 2>),
     /// Or predicate, for example, `a > 10 OR b < 20`.
@@ -367,6 +371,8 @@ impl Bind for Predicate {
                     bound_literals,
                 )))
             }
+            Predicate::AlwaysTrue => Ok(BoundPredicate::AlwaysTrue),
+            Predicate::AlwaysFalse => Ok(BoundPredicate::AlwaysFalse),
         }
     }
 }
@@ -374,6 +380,12 @@ impl Bind for Predicate {
 impl Display for Predicate {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         match self {
+            Predicate::AlwaysTrue => {
+                write!(f, "TRUE")
+            }
+            Predicate::AlwaysFalse => {
+                write!(f, "FALSE")
+            }
             Predicate::And(expr) => {
                 write!(f, "({}) AND ({})", expr.inputs()[0], expr.inputs()[1])
             }
@@ -461,6 +473,8 @@ impl Predicate {
     /// ```
     pub fn negate(self) -> Predicate {
         match self {
+            Predicate::AlwaysTrue => Predicate::AlwaysFalse,
+            Predicate::AlwaysFalse => Predicate::AlwaysTrue,
             Predicate::And(expr) => Predicate::Or(LogicalExpression::new(
                 expr.inputs.map(|expr| Box::new(expr.negate())),
             )),
@@ -525,6 +539,8 @@ impl Predicate {
             Predicate::Unary(expr) => Predicate::Unary(expr),
             Predicate::Binary(expr) => Predicate::Binary(expr),
             Predicate::Set(expr) => Predicate::Set(expr),
+            Predicate::AlwaysTrue => Predicate::AlwaysTrue,
+            Predicate::AlwaysFalse => Predicate::AlwaysFalse,
         }
     }
 }