Add LogicalOptimizerRule trait

bustubx/src/optimizer/logical_optimizer.rs

@@ -0,0 +1,46 @@
+use crate::error::BustubxResult;
+use crate::planner::logical_plan::LogicalPlan;
+use std::sync::Arc;
+
+/// `LogicalOptimizerRule` transforms one [`LogicalPlan`] into another which
+/// computes the same results, but in a potentially more efficient
+/// way. If there are no suitable transformations for the input plan,
+/// the optimizer can simply return it as is.
+pub trait LogicalOptimizerRule {
+    /// Try and rewrite `plan` to an optimized form, returning None if the plan cannot be
+    /// optimized by this rule.
+    fn try_optimize(&self, plan: &LogicalPlan) -> BustubxResult<Option<LogicalPlan>>;
+
+    /// A human readable name for this optimizer rule
+    fn name(&self) -> &str;
+
+    /// How should the rule be applied by the optimizer
+    ///
+    /// If a rule use default None, it should traverse recursively plan inside itself
+    fn apply_order(&self) -> Option<ApplyOrder> {
+        None
+    }
+}
+
+pub enum ApplyOrder {
+    TopDown,
+    BottomUp,
+}
+
+#[derive(Clone)]
+pub struct LogicalOptimizer {
+    /// All optimizer rules to apply
+    pub rules: Vec<Arc<dyn LogicalOptimizerRule + Send + Sync>>,
+}
+
+impl LogicalOptimizer {
+    pub fn new() -> Self {
+        let rules: Vec<Arc<dyn LogicalOptimizerRule + Sync + Send>> = vec![];
+
+        Self { rules }
+    }
+
+    pub fn optimize(&self, plan: &LogicalPlan) -> BustubxResult<LogicalPlan> {
+        todo!()
+    }
+}

bustubx/src/optimizer/mod.rs

@@ -4,9 +4,12 @@ use crate::planner::logical_plan::LogicalPlan;
 
 use self::{physical_optimizer::PhysicalOptimizer, physical_plan::PhysicalPlan};
 
+mod logical_optimizer;
 pub mod physical_optimizer;
 pub mod physical_plan;
 
+pub use logical_optimizer::{LogicalOptimizer, LogicalOptimizerRule};
+
 pub struct Optimizer {
     physical_optimizer: PhysicalOptimizer,
 }