sql: use Rows in Engine trait

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 {

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

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};

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 {

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 {

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).
 ///