diff --git a/src/sql/engine/engine.rs b/src/sql/engine/engine.rs
index b2c8a0589..5e9738ea3 100644
--- a/src/sql/engine/engine.rs
+++ b/src/sql/engine/engine.rs
@@ -4,7 +4,7 @@ use super::Session;
 use crate::errinput;
 use crate::error::Result;
 use crate::sql::types::schema::Table;
-use crate::sql::types::{Expression, Row, Value};
+use crate::sql::types::{Expression, Row, Rows, Value};
 
 use std::collections::HashSet;
 
@@ -53,18 +53,16 @@ pub trait Transaction: Catalog {
     /// Reads an index entry, if it exists
     fn read_index(&self, table: &str, column: &str, value: &Value) -> Result<HashSet<Value>>;
     /// Scans a table's rows
-    fn scan(&self, table: &str, filter: Option<Expression>) -> Result<Scan>;
-    /// Scans a column's index entries
+    fn scan(&self, table: &str, filter: Option<Expression>) -> Result<Rows>;
+    /// Scans a column's index entries.
+    /// TODO: this is only used for tests. Remove it?
     fn scan_index(&self, table: &str, column: &str) -> Result<IndexScan>;
     /// Updates a table row
     fn update(&mut self, table: &str, id: &Value, row: Row) -> Result<()>;
 }
 
-/// A row scan iterator
-pub type Scan = Box<dyn DoubleEndedIterator<Item = Result<Row>> + Send>;
-
-/// An index scan iterator
-pub type IndexScan = Box<dyn DoubleEndedIterator<Item = Result<(Value, HashSet<Value>)>> + Send>;
+/// An index scan iterator.
+pub type IndexScan = Box<dyn Iterator<Item = Result<(Value, HashSet<Value>)>>>;
 
 /// The catalog stores schema information
 pub trait Catalog {
diff --git a/src/sql/engine/local.rs b/src/sql/engine/local.rs
index c539be808..fbfcc9227 100644
--- a/src/sql/engine/local.rs
+++ b/src/sql/engine/local.rs
@@ -1,5 +1,5 @@
 use super::super::types::schema::Table;
-use super::super::types::{Expression, Row, Value};
+use super::super::types::{Expression, Row, Rows, Value};
 use super::{Catalog, Transaction as _};
 use crate::encoding::{self, Key as _, Value as _};
 use crate::error::Result;
@@ -191,7 +191,7 @@ impl<E: storage::Engine> super::Transaction for Transaction<E> {
         self.index_load(table, column, value)
     }
 
-    fn scan(&self, table: &str, filter: Option<Expression>) -> Result<super::Scan> {
+    fn scan(&self, table: &str, filter: Option<Expression>) -> Result<Rows> {
         let table = self.must_read_table(table)?;
         Ok(Box::new(
             self.txn
diff --git a/src/sql/engine/mod.rs b/src/sql/engine/mod.rs
index 8f5c421ff..8cd06658b 100644
--- a/src/sql/engine/mod.rs
+++ b/src/sql/engine/mod.rs
@@ -3,7 +3,7 @@ mod local;
 mod raft;
 mod session;
 
-pub use engine::{Catalog, Engine, IndexScan, Scan, Transaction};
+pub use engine::{Catalog, Engine, IndexScan, Transaction};
 pub use local::Local;
 pub use raft::{Raft, Status};
 pub use session::{Session, StatementResult};
diff --git a/src/sql/engine/raft.rs b/src/sql/engine/raft.rs
index 0663a76ab..a111d5ec3 100644
--- a/src/sql/engine/raft.rs
+++ b/src/sql/engine/raft.rs
@@ -1,6 +1,6 @@
 use super::super::types::schema::Table;
-use super::super::types::{Expression, Row, Value};
-use super::{Catalog, Engine as _, IndexScan, Scan, Transaction as _};
+use super::super::types::{Expression, Row, Rows, Value};
+use super::{Catalog, Engine as _, IndexScan, Transaction as _};
 use crate::encoding::{self, bincode, Value as _};
 use crate::errdata;
 use crate::error::Result;
@@ -232,7 +232,7 @@ impl super::Transaction for Transaction {
         })
     }
 
-    fn scan(&self, table: &str, filter: Option<Expression>) -> Result<Scan> {
+    fn scan(&self, table: &str, filter: Option<Expression>) -> Result<Rows> {
         Ok(Box::new(
             self.client
                 .query::<Vec<_>>(Query::Scan {
diff --git a/src/sql/execution/execute.rs b/src/sql/execution/execute.rs
index f2b86c753..7015820dd 100644
--- a/src/sql/execution/execute.rs
+++ b/src/sql/execution/execute.rs
@@ -7,7 +7,7 @@ use super::source::{IndexLookup, KeyLookup, Nothing, Scan};
 use crate::error::Result;
 use crate::sql::engine::Transaction;
 use crate::sql::plan::{Node, Plan};
-use crate::sql::types::{Columns, Row};
+use crate::sql::types::{Columns, Row, Rows};
 
 /// A plan execution result.
 pub enum ExecutionResult {
@@ -23,8 +23,7 @@ pub enum ExecutionResult {
 pub struct QueryIterator {
     // TODO: use a different type here.
     pub columns: Columns,
-    // TODO: remove Send, it's only needed for the ResultSet conversion.
-    pub rows: Box<dyn Iterator<Item = Result<Row>> + Send>,
+    pub rows: Rows,
 }
 
 impl Iterator for QueryIterator {
diff --git a/src/sql/types/value.rs b/src/sql/types/value.rs
index 221b40648..46eaa76cc 100644
--- a/src/sql/types/value.rs
+++ b/src/sql/types/value.rs
@@ -193,7 +193,7 @@ pub type Row = Vec<Value>;
 /// A row iterator.
 ///
 /// TODO: try to avoid boxing here.
-pub type Rows = Box<dyn Iterator<Item = Result<Row>> + Send>;
+pub type Rows = Box<dyn Iterator<Item = Result<Row>>>;
 
 /// A column (in a result set, see schema::Column for table columns).
 ///