feat: DSL Engine and HIR (#34)

# OPTD Engine Implementation

This PR implements the OPTD engine that serves as the interface between
the DSL and the optimizer driver. The engine provides the essential APIs
for rule application, cost model integration, and catalog access that
drive the exploration process. It enables efficient query plan
transformations while managing the complexity of multiple possible
transformation paths.

optd-core/Cargo.toml

@@ -14,4 +14,5 @@ proc-macro2.workspace = true
 sqlx = { version = "0.8", features = [ "sqlite", "runtime-tokio", "migrate" ] }
 serde = { version = "1.0", features = ["derive"] }
 serde_json = { version = "1", features = ["raw_value"] }
-dotenvy = "0.15"
+dotenvy = "0.15"
+ordered-float = { version = "5.0.0", features = ["serde"] }

optd-core/src/cascades/expressions.rs

@@ -1,21 +1,22 @@
 //! Types for logical and physical expressions in the optimizer.
 
+use crate::operators::relational::logical::LogicalOperator;
 use crate::operators::relational::physical::PhysicalOperator;
 use crate::operators::scalar::ScalarOperator;
-use crate::{operators::relational::logical::LogicalOperator, values::OptdValue};
 use serde::Deserialize;
 
 use super::goal::GoalId;
 use super::groups::{RelationalGroupId, ScalarGroupId};
+use super::ir::OperatorData;
 
 /// A logical expression in the memo table.
-pub type LogicalExpression = LogicalOperator<OptdValue, RelationalGroupId, ScalarGroupId>;
+pub type LogicalExpression = LogicalOperator<OperatorData, RelationalGroupId, ScalarGroupId>;
 
 /// A physical expression in the memo table.
-pub type PhysicalExpression = PhysicalOperator<OptdValue, GoalId, ScalarGroupId>;
+pub type PhysicalExpression = PhysicalOperator<OperatorData, GoalId, ScalarGroupId>;
 
 /// A scalar expression in the memo table.
-pub type ScalarExpression = ScalarOperator<OptdValue, ScalarGroupId>;
+pub type ScalarExpression = ScalarOperator<OperatorData, ScalarGroupId>;
 
 /// A unique identifier for a logical expression in the memo table.
 #[repr(transparent)]

optd-core/src/cascades/ir.rs

@@ -0,0 +1,74 @@
+use super::groups::{RelationalGroupId, ScalarGroupId};
+use ordered_float::OrderedFloat;
+use serde::{Deserialize, Serialize};
+
+#[derive(Clone, PartialEq, Debug, Serialize, Deserialize)]
+pub enum OperatorData {
+    Int64(i64),
+    Float64(OrderedFloat<f64>),
+    String(String),
+    Bool(bool),
+    Struct(String, Vec<OperatorData>),
+    Array(Vec<OperatorData>),
+}
+
+impl OperatorData {
+    pub fn as_str(&self) -> Option<&str> {
+        match self {
+            OperatorData::String(s) => Some(s),
+            _ => None,
+        }
+    }
+
+    pub fn as_bool(&self) -> Option<bool> {
+        match self {
+            OperatorData::Bool(b) => Some(*b),
+            _ => None,
+        }
+    }
+
+    pub fn as_i64(&self) -> Option<i64> {
+        match self {
+            OperatorData::Int64(i) => Some(*i),
+            _ => None,
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum Children<T> {
+    Singleton(T),
+    VarLength(Vec<T>),
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum PartialLogicalPlan {
+    PartialMaterialized {
+        tag: String,
+        data: Vec<OperatorData>,
+        relational_children: Vec<Children<PartialLogicalPlan>>,
+        scalar_children: Vec<Children<PartialScalarPlan>>,
+    },
+    UnMaterialized(RelationalGroupId),
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum PartialScalarPlan {
+    PartialMaterialized {
+        tag: String,
+        data: Vec<OperatorData>,
+        scalar_children: Vec<Children<PartialScalarPlan>>,
+    },
+    UnMaterialized(ScalarGroupId),
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum PartialPhysicalPlan {
+    PartialMaterialized {
+        tag: String,
+        data: Vec<OperatorData>,
+        relational_children: Vec<Children<PartialPhysicalPlan>>,
+        scalar_children: Vec<Children<PartialScalarPlan>>,
+    },
+    UnMaterialized(RelationalGroupId),
+}

optd-core/src/cascades/mod.rs

@@ -1,6 +1,7 @@
 pub mod expressions;
 pub mod goal;
 pub mod groups;
+pub mod ir;
 pub mod memo;
 pub mod properties;
 

optd-core/src/cascades/properties/mod.rs

@@ -1,6 +1,6 @@
 use serde::{Deserialize, Serialize};
 
-use crate::values::OptdValue;
+use crate::cascades::ir::OperatorData;
 
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize, Default)]
 pub struct PhysicalProperties {
@@ -11,5 +11,5 @@ pub struct PhysicalProperties {
 pub struct SortProperty {
     /// Each tuple is a column index, direction pair.
     /// e.g. vec![(0, Asc), (1, Desc)]
-    pub sort_orders: Vec<(OptdValue, OptdValue)>,
+    pub sort_orders: Vec<(OperatorData, OperatorData)>,
 }