diff --git a/lykiadb-lang/src/ast/visitor.rs b/lykiadb-lang/src/ast/visitor.rs
index 81fbed4..d5c07bf 100644
--- a/lykiadb-lang/src/ast/visitor.rs
+++ b/lykiadb-lang/src/ast/visitor.rs
@@ -6,6 +6,10 @@ use super::{
     stmt::Stmt,
 };
 
+pub trait ExprEvaluator<O, E> {
+    fn eval(&mut self, e: &Expr) -> Result<O, E>;
+}
+
 pub trait Visitor<O, E> {
     fn visit_expr(&self, e: &Expr) -> Result<O, E>;
     fn visit_stmt(&self, s: &Stmt) -> Result<O, E>;
diff --git a/lykiadb-server/src/engine/interpreter.rs b/lykiadb-server/src/engine/interpreter.rs
index 4a8db26..fbc64c5 100644
--- a/lykiadb-server/src/engine/interpreter.rs
+++ b/lykiadb-server/src/engine/interpreter.rs
@@ -1,6 +1,6 @@
 use lykiadb_lang::ast::expr::{Expr, Operation};
 use lykiadb_lang::ast::stmt::Stmt;
-use lykiadb_lang::ast::visitor::VisitorMut;
+use lykiadb_lang::ast::visitor::{ExprEvaluator, VisitorMut};
 use lykiadb_lang::parser::program::Program;
 use lykiadb_lang::parser::resolver::Resolver;
 use lykiadb_lang::parser::Parser;
@@ -71,12 +71,6 @@ pub enum InterpretError {
         span: Span,
         property: String,
     },
-    /*AssignmentToUndefined {
-        token: Token,
-    },
-    VariableNotFound {
-        token: Token,
-    },*/
     Other {
         message: String,
     }, // TODO(vck): Refactor this
@@ -180,7 +174,12 @@ pub struct Interpreter {
     env_man: Shared<Environment>,
     source_processor: SourceProcessor,
     current_program: Option<Arc<Program>>,
-    planner: Planner
+}
+
+impl ExprEvaluator<RV, HaltReason> for Interpreter {
+    fn eval(&mut self, e: &Expr) -> Result<RV, HaltReason> {
+        self.visit_expr(e)
+    }
 }
 
 impl Interpreter {
@@ -193,7 +192,6 @@ impl Interpreter {
             loop_stack: LoopStack::new(),
             source_processor: SourceProcessor::new(),
             current_program: None,
-            planner: Planner::new()
         }
     }
 
@@ -328,7 +326,11 @@ impl VisitorMut<RV, HaltReason> for Interpreter {
             Expr::Select { .. } |
             Expr::Insert { .. } |
             Expr::Update { .. } | 
-            Expr::Delete { .. } => /*self.planner.build(&e)*/ Ok(RV::NaN),
+            Expr::Delete { .. } => {
+                let mut planner = Planner::new();
+                let plan = planner.build(e)?;
+                Ok(RV::Undefined)
+            },
             Expr::Literal {
                 value,
                 raw: _,
diff --git a/lykiadb-server/src/net/tcp.rs b/lykiadb-server/src/net/tcp.rs
index 4f5dca5..72f9720 100644
--- a/lykiadb-server/src/net/tcp.rs
+++ b/lykiadb-server/src/net/tcp.rs
@@ -18,7 +18,6 @@ impl TcpConnection {
 
     pub async fn read(&mut self) -> Result<Option<Message>, CommunicationError> {
         loop {
-            // TODO(vck): Replace .to_vec call with something cheaper
             if let Ok(parsed) = bson::from_slice::<Message>(&self.read_buffer) {
                 self.read_buffer.clear();
                 return Ok(Some(parsed));
diff --git a/lykiadb-server/src/plan/mod.rs b/lykiadb-server/src/plan/mod.rs
index e69de29..446a2ab 100644
--- a/lykiadb-server/src/plan/mod.rs
+++ b/lykiadb-server/src/plan/mod.rs
@@ -0,0 +1,42 @@
+use lykiadb_lang::ast::sql::SqlExpr;
+use serde::{Deserialize, Serialize};
+pub mod planner;
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub enum Aggregate {
+    Average(SqlExpr),
+    Count(SqlExpr),
+    Max(SqlExpr),
+    Min(SqlExpr),
+    Sum(SqlExpr),
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub enum Direction {
+    Ascending,
+    Descending,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub enum Plan {
+    Select(Node)
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub enum Node {
+    Aggregate { source: Box<Node>, group_by: Vec<SqlExpr>, aggregates: Vec<Aggregate> },
+
+    Filter { source: Box<Node>, predicate: SqlExpr },
+
+    Projection { source: Box<Node>, expressions: Vec<SqlExpr>, aliases: Vec<String> },
+    
+    Scan { collection: String, filter: Option<SqlExpr>, alias: Option<String> },
+
+    Limit { source: Box<Node>, limit: usize },
+
+    Offset { source: Box<Node>, offset: usize },
+
+    Order { source: Box<Node>, key: Vec<(SqlExpr, Direction)> },
+
+    Values { rows: Vec<Vec<SqlExpr>> },
+}
\ No newline at end of file
diff --git a/lykiadb-server/src/plan/planner.rs b/lykiadb-server/src/plan/planner.rs
new file mode 100644
index 0000000..bdbca03
--- /dev/null
+++ b/lykiadb-server/src/plan/planner.rs
@@ -0,0 +1,28 @@
+use lykiadb_lang::ast::{expr::Expr, sql::SqlSelect, visitor::ExprEvaluator};
+
+use crate::{engine::interpreter::HaltReason, value::types::RV};
+
+use super::{Node, Plan};
+pub struct Planner;
+
+impl Planner {
+    pub fn new() -> Planner {
+        Planner {}
+    }
+
+    pub fn build(&mut self, expr: &Expr) -> Result<Plan, HaltReason> {
+        match expr {
+            Expr::Select { 
+                query,
+                span: _,
+                id: _ } => {
+                self.build_select(query)
+            },
+            _ => panic!("Not implemented yet.")
+        }
+    }
+
+    fn build_select(&mut self, query: &SqlSelect) -> Result<Plan, HaltReason> {
+        Ok(Plan::Select(Node::Values { rows: vec![vec![]] }))
+    }
+}
\ No newline at end of file
diff --git a/lykiadb-server/src/plan/tree.rs b/lykiadb-server/src/plan/tree.rs
deleted file mode 100644
index e69de29..0000000
diff --git a/lykiadb-server/src/value/environment.rs b/lykiadb-server/src/value/environment.rs
index 8e749a4..64dc580 100644
--- a/lykiadb-server/src/value/environment.rs
+++ b/lykiadb-server/src/value/environment.rs
@@ -30,6 +30,12 @@ impl Default for Environment {
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub enum EnvironmentError {
+    /*AssignmentToUndefined {
+        token: Token,
+    },
+    VariableNotFound {
+        token: Token,
+    },*/
     Other {
         message: String,
     }