Reduce memory allocations

Fixes #26

core/btree.rs

@@ -1,6 +1,6 @@
 use crate::pager::Pager;
 use crate::sqlite3_ondisk::{BTreeCell, TableInteriorCell, TableLeafCell};
-use crate::types::Record;
+use crate::types::OwnedRecord;
 
 use anyhow::Result;
 
@@ -42,7 +42,7 @@ pub struct Cursor {
     root_page: usize,
     page: RefCell<Option<Arc<MemPage>>>,
     rowid: RefCell<Option<u64>>,
-    record: RefCell<Option<Record>>,
+    record: RefCell<Option<OwnedRecord>>,
 }
 
 impl Cursor {
@@ -97,7 +97,7 @@ impl Cursor {
         Ok(self.rowid.borrow())
     }
 
-    pub fn record(&self) -> Result<Ref<Option<Record>>> {
+    pub fn record(&self) -> Result<Ref<Option<OwnedRecord>>> {
         Ok(self.record.borrow())
     }
 
@@ -105,7 +105,7 @@ impl Cursor {
         self.record.borrow().is_some()
     }
 
-    fn get_next_record(&mut self) -> Result<CursorResult<(Option<u64>, Option<Record>)>> {
+    fn get_next_record(&mut self) -> Result<CursorResult<(Option<u64>, Option<OwnedRecord>)>> {
         loop {
             let mem_page = {
                 let mem_page = self.page.borrow();
@@ -152,7 +152,7 @@ impl Cursor {
                 }
                 BTreeCell::TableLeafCell(TableLeafCell { _rowid, _payload }) => {
                     mem_page.advance();
-                    let record = crate::sqlite3_ondisk::read_record(_payload)?;
+                    let record= crate::sqlite3_ondisk::read_record(_payload)?;
                     return Ok(CursorResult::Ok((Some(*_rowid), Some(record))));
                 }
             }

core/lib.rs

@@ -100,10 +100,7 @@ impl Connection {
             match cmd {
                 Cmd::Stmt(stmt) => {
                     let program = Arc::new(translate::translate(&self.schema, stmt)?);
-                    Ok(Statement {
-                        program,
-                        pager: self.pager.clone(),
-                    })
+                    Ok(Statement::new(program, self.pager.clone()))
                 }
                 Cmd::Explain(_stmt) => todo!(),
                 Cmd::ExplainQueryPlan(_stmt) => todo!(),
@@ -121,8 +118,8 @@ impl Connection {
             match cmd {
                 Cmd::Stmt(stmt) => {
                     let program = Arc::new(translate::translate(&self.schema, stmt)?);
-                    let state = vdbe::ProgramState::new(program.max_registers);
-                    Ok(Some(Rows::new(state, program, self.pager.clone())))
+                    let stmt = Statement::new(program, self.pager.clone());
+                    Ok(Some(Rows { stmt }))
                 }
                 Cmd::Explain(stmt) => {
                     let program = translate::translate(&self.schema, stmt)?;
@@ -160,40 +157,21 @@ impl Connection {
 
 pub struct Statement {
     program: Arc<vdbe::Program>,
+    state: vdbe::ProgramState,
     pager: Arc<Pager>,
 }
 
 impl Statement {
-    pub fn query(&self) -> Result<Rows> {
-        let state = vdbe::ProgramState::new(self.program.max_registers);
-        Ok(Rows::new(state, self.program.clone(), self.pager.clone()))
-    }
-
-    pub fn reset(&self) {}
-}
-
-pub enum RowResult {
-    Row(Row),
-    IO,
-    Done,
-}
-
-pub struct Rows {
-    state: vdbe::ProgramState,
-    program: Arc<vdbe::Program>,
-    pager: Arc<Pager>,
-}
-
-impl Rows {
-    pub fn new(state: vdbe::ProgramState, program: Arc<vdbe::Program>, pager: Arc<Pager>) -> Self {
+    pub fn new(program: Arc<vdbe::Program>, pager: Arc<Pager>) -> Self {
+        let state = vdbe::ProgramState::new(program.max_registers);
         Self {
-            state,
             program,
+            state,
             pager,
         }
     }
 
-    pub fn next(&mut self) -> Result<RowResult> {
+    pub fn step<'a>(&'a mut self) -> Result<RowResult<'a>> {
         loop {
             let result = self.program.step(&mut self.state, self.pager.clone())?;
             match result {
@@ -209,15 +187,42 @@ impl Rows {
             }
         }
     }
+
+    pub fn query(&mut self) -> Result<Rows> {
+        let stmt = Statement::new(self.program.clone(), self.pager.clone());
+        Ok(Rows::new(stmt))
+    }
+
+    pub fn reset(&self) {}
 }
 
-pub struct Row {
-    pub values: Vec<Value>,
+pub enum RowResult<'a> {
+    Row(Row<'a>),
+    IO,
+    Done,
 }
 
-impl Row {
+pub struct Row<'a> {
+    pub values: Vec<Value<'a>>,
+}
+
+impl<'a> Row<'a> {
     pub fn get<T: crate::types::FromValue>(&self, idx: usize) -> Result<T> {
         let value = &self.values[idx];
         T::from_value(value)
     }
 }
+
+pub struct Rows {
+    stmt: Statement,
+}
+
+impl Rows {
+    pub fn new(stmt: Statement) -> Self {
+        Self { stmt }
+    }
+
+    pub fn next<'a>(&'a mut self) -> Result<RowResult<'a>> {
+        self.stmt.step()
+    }
+}

core/sqlite3_ondisk.rs

@@ -26,10 +26,9 @@
 use crate::buffer_pool::BufferPool;
 use crate::io::{Buffer, Completion};
 use crate::pager::Page;
-use crate::types::{Record, Value};
+use crate::types::{OwnedRecord, OwnedValue};
 use crate::PageSource;
 use anyhow::{anyhow, Result};
-use std::rc::Rc;
 use std::sync::{Arc, Mutex};
 use log::trace;
 
@@ -296,7 +295,7 @@ impl TryFrom<u64> for SerialType {
     }
 }
 
-pub fn read_record(payload: &[u8]) -> Result<Record> {
+pub fn read_record(payload: &[u8]) -> Result<OwnedRecord> {
     let mut pos = 0;
     let (header_size, nr) = read_varint(payload)?;
     assert!((header_size as usize) >= nr);
@@ -318,24 +317,24 @@ pub fn read_record(payload: &[u8]) -> Result<Record> {
         pos += usize;
         values.push(value);
     }
-    Ok(Record { values })
+    Ok(OwnedRecord { values })
 }
 
-pub fn read_value(buf: &[u8], serial_type: &SerialType) -> Result<(Value, usize)> {
+pub fn read_value(buf: & [u8], serial_type: &SerialType) -> Result<(OwnedValue, usize)> {
     match *serial_type {
-        SerialType::Null => Ok((Value::Null, 0)),
+        SerialType::Null => Ok((OwnedValue::Null, 0)),
         SerialType::UInt8 => {
             if buf.len() < 1 {
                 return Err(anyhow!("Invalid UInt8 value"));
             }
-            Ok((Value::Integer(buf[0] as i64), 1))
+            Ok((OwnedValue::Integer(buf[0] as i64), 1))
         }
         SerialType::BEInt16 => {
             if buf.len() < 2 {
                 return Err(anyhow!("Invalid BEInt16 value"));
             }
             Ok((
-                Value::Integer(i16::from_be_bytes([buf[0], buf[1]]) as i64),
+                OwnedValue::Integer(i16::from_be_bytes([buf[0], buf[1]]) as i64),
                 2,
             ))
         }
@@ -344,7 +343,7 @@ pub fn read_value(buf: &[u8], serial_type: &SerialType) -> Result<(Value, usize)
                 return Err(anyhow!("Invalid BEInt24 value"));
             }
             Ok((
-                Value::Integer(i32::from_be_bytes([0, buf[0], buf[1], buf[2]]) as i64),
+                OwnedValue::Integer(i32::from_be_bytes([0, buf[0], buf[1], buf[2]]) as i64),
                 3,
             ))
         }
@@ -353,7 +352,7 @@ pub fn read_value(buf: &[u8], serial_type: &SerialType) -> Result<(Value, usize)
                 return Err(anyhow!("Invalid BEInt32 value"));
             }
             Ok((
-                Value::Integer(i32::from_be_bytes([buf[0], buf[1], buf[2], buf[3]]) as i64),
+                OwnedValue::Integer(i32::from_be_bytes([buf[0], buf[1], buf[2], buf[3]]) as i64),
                 4,
             ))
         }
@@ -362,7 +361,7 @@ pub fn read_value(buf: &[u8], serial_type: &SerialType) -> Result<(Value, usize)
                 return Err(anyhow!("Invalid BEInt48 value"));
             }
             Ok((
-                Value::Integer(i64::from_be_bytes([
+                OwnedValue::Integer(i64::from_be_bytes([
                     0, 0, buf[0], buf[1], buf[2], buf[3], buf[4], buf[5],
                 ])),
                 6,
@@ -373,7 +372,7 @@ pub fn read_value(buf: &[u8], serial_type: &SerialType) -> Result<(Value, usize)
                 return Err(anyhow!("Invalid BEInt64 value"));
             }
             Ok((
-                Value::Integer(i64::from_be_bytes([
+                OwnedValue::Integer(i64::from_be_bytes([
                     buf[0], buf[1], buf[2], buf[3], buf[4], buf[5], buf[6], buf[7],
                 ])),
                 8,
@@ -384,19 +383,19 @@ pub fn read_value(buf: &[u8], serial_type: &SerialType) -> Result<(Value, usize)
                 return Err(anyhow!("Invalid BEFloat64 value"));
             }
             Ok((
-                Value::Float(f64::from_be_bytes([
+                OwnedValue::Float(f64::from_be_bytes([
                     buf[0], buf[1], buf[2], buf[3], buf[4], buf[5], buf[6], buf[7],
                 ])),
                 8,
             ))
         }
-        SerialType::ConstInt0 => Ok((Value::Integer(0), 0)),
-        SerialType::ConstInt1 => Ok((Value::Integer(1), 0)),
+        SerialType::ConstInt0 => Ok((OwnedValue::Integer(0), 0)),
+        SerialType::ConstInt1 => Ok((OwnedValue::Integer(1), 0)),
         SerialType::Blob(n) => {
             if buf.len() < n {
                 return Err(anyhow!("Invalid Blob value"));
             }
-            Ok((Value::Blob(buf[0..n].to_vec()), n))
+            Ok((OwnedValue::Blob(buf[0..n].to_vec()), n))
         }
         SerialType::String(n) => {
             if buf.len() < n {
@@ -404,7 +403,7 @@ pub fn read_value(buf: &[u8], serial_type: &SerialType) -> Result<(Value, usize)
             }
             let bytes = buf[0..n].to_vec();
             let value = unsafe { String::from_utf8_unchecked(bytes) };
-            Ok((Value::Text(Rc::new(value)), n))
+            Ok((OwnedValue::Text(value), n))
         }
     }
 }
@@ -458,22 +457,22 @@ mod tests {
     }
 
     #[rstest]
-    #[case(&[], SerialType::Null, Value::Null)]
-    #[case(&[255], SerialType::UInt8, Value::Integer(255))]
-    #[case(&[0x12, 0x34], SerialType::BEInt16, Value::Integer(0x1234))]
-    #[case(&[0x12, 0x34, 0x56], SerialType::BEInt24, Value::Integer(0x123456))]
-    #[case(&[0x12, 0x34, 0x56, 0x78], SerialType::BEInt32, Value::Integer(0x12345678))]
-    #[case(&[0x12, 0x34, 0x56, 0x78, 0x9A, 0xBC], SerialType::BEInt48, Value::Integer(0x123456789ABC))]
-    #[case(&[0x12, 0x34, 0x56, 0x78, 0x9A, 0xBC, 0xDE, 0xFF], SerialType::BEInt64, Value::Integer(0x123456789ABCDEFF))]
-    #[case(&[64, 9, 33, 251, 84, 68, 45, 24], SerialType::BEFloat64, Value::Float(3.141592653589793))]
-    #[case(&[], SerialType::ConstInt0, Value::Integer(0))]
-    #[case(&[], SerialType::ConstInt1, Value::Integer(1))]
-    #[case(&[1, 2, 3], SerialType::Blob(3), Value::Blob(vec![1, 2, 3]))]
-    #[case(&[65, 66, 67], SerialType::String(3), Value::Text("ABC".to_string().into()))]
+    #[case(&[], SerialType::Null, OwnedValue::Null)]
+    #[case(&[255], SerialType::UInt8, OwnedValue::Integer(255))]
+    #[case(&[0x12, 0x34], SerialType::BEInt16, OwnedValue::Integer(0x1234))]
+    #[case(&[0x12, 0x34, 0x56], SerialType::BEInt24, OwnedValue::Integer(0x123456))]
+    #[case(&[0x12, 0x34, 0x56, 0x78], SerialType::BEInt32, OwnedValue::Integer(0x12345678))]
+    #[case(&[0x12, 0x34, 0x56, 0x78, 0x9A, 0xBC], SerialType::BEInt48, OwnedValue::Integer(0x123456789ABC))]
+    #[case(&[0x12, 0x34, 0x56, 0x78, 0x9A, 0xBC, 0xDE, 0xFF], SerialType::BEInt64, OwnedValue::Integer(0x123456789ABCDEFF))]
+    #[case(&[64, 9, 33, 251, 84, 68, 45, 24], SerialType::BEFloat64, OwnedValue::Float(3.141592653589793))]
+    #[case(&[], SerialType::ConstInt0, OwnedValue::Integer(0))]
+    #[case(&[], SerialType::ConstInt1, OwnedValue::Integer(1))]
+    #[case(&[1, 2, 3], SerialType::Blob(3), OwnedValue::Blob(vec![1, 2, 3]))]
+    #[case(&[65, 66, 67], SerialType::String(3), OwnedValue::Text("ABC".to_string()))]
     fn test_read_value(
         #[case] buf: &[u8],
         #[case] serial_type: SerialType,
-        #[case] expected: Value,
+        #[case] expected: OwnedValue,
     ) {
         let result = read_value(buf, &serial_type).unwrap();
         assert_eq!(result, (expected, buf.len()));

core/types.rs

@@ -1,16 +1,33 @@
-use std::rc::Rc;
-
 use anyhow::Result;
 
 #[derive(Debug, Clone, PartialEq)]
-pub enum Value {
+pub enum Value<'a> {
     Null,
     Integer(i64),
     Float(f64),
-    Text(Rc<String>),
+    Text(&'a String),
+    Blob(&'a Vec<u8>),
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum OwnedValue {
+    Null,
+    Integer(i64),
+    Float(f64),
+    Text(String),
     Blob(Vec<u8>),
 }
 
+pub fn to_value<'a>(value: &'a OwnedValue) -> Value<'a> {
+    match value {
+        OwnedValue::Null => Value::Null,
+        OwnedValue::Integer(i) => Value::Integer(*i),
+        OwnedValue::Float(f) => Value::Float(*f),
+        OwnedValue::Text(s) => Value::Text(s),
+        OwnedValue::Blob(b) => Value::Blob(b),
+    }
+}
+
 pub trait FromValue {
     fn from_value(value: &Value) -> Result<Self>
     where
@@ -36,12 +53,22 @@ impl FromValue for String {
 }
 
 #[derive(Debug)]
-pub struct Record {
-    pub values: Vec<Value>,
+pub struct Record<'a> {
+    pub values: Vec<Value<'a>>,
 }
 
-impl Record {
-    pub fn new(values: Vec<Value>) -> Self {
+impl<'a> Record<'a> {
+    pub fn new(values: Vec<Value<'a>>) -> Self {
         Self { values }
     }
 }
+
+pub struct OwnedRecord {
+    pub values: Vec<OwnedValue>,
+}
+
+impl OwnedRecord {
+    pub fn new(values: Vec<OwnedValue>) -> Self {
+        Self { values }
+    }
+}

core/vdbe.rs

@@ -1,8 +1,9 @@
 use crate::btree::{Cursor, CursorResult};
 use crate::pager::Pager;
-use crate::types::{Record, Value};
+use crate::types::{OwnedValue, Record};
 
 use anyhow::Result;
+use std::cell::RefCell;
 use std::collections::BTreeMap;
 use std::sync::Arc;
 
@@ -143,24 +144,24 @@ impl ProgramBuilder {
     }
 }
 
-pub enum StepResult {
+pub enum StepResult<'a> {
     Done,
     IO,
-    Row(Record),
+    Row(Record<'a>),
 }
 
 /// The program state describes the environment in which the program executes.
 pub struct ProgramState {
     pub pc: usize,
-    cursors: BTreeMap<usize, Cursor>,
-    registers: Vec<Value>,
+    cursors: RefCell<BTreeMap<usize, Cursor>>,
+    registers: Vec<OwnedValue>,
 }
 
 impl ProgramState {
     pub fn new(max_registers: usize) -> Self {
-        let cursors = BTreeMap::new();
+        let cursors = RefCell::new(BTreeMap::new());
         let mut registers = Vec::with_capacity(max_registers);
-        registers.resize(max_registers, Value::Null);
+        registers.resize(max_registers, OwnedValue::Null);
         Self {
             pc: 0,
             cursors,
@@ -191,10 +192,11 @@ impl Program {
         }
     }
 
-    pub fn step(&self, state: &mut ProgramState, pager: Arc<Pager>) -> Result<StepResult> {
+    pub fn step<'a>(&self, state: &'a mut ProgramState, pager: Arc<Pager>) -> Result<StepResult<'a>> {
         loop {
             let insn = &self.insns[state.pc];
             trace_insn(state.pc, insn);
+            let mut cursors = state.cursors.borrow_mut();
             match insn {
                 Insn::Init { target_pc } => {
                     state.pc = *target_pc;
@@ -204,14 +206,14 @@ impl Program {
                     root_page,
                 } => {
                     let cursor = Cursor::new(pager.clone(), *root_page);
-                    state.cursors.insert(*cursor_id, cursor);
+                    cursors.insert(*cursor_id, cursor);
                     state.pc += 1;
                 }
                 Insn::OpenReadAwait => {
                     state.pc += 1;
                 }
                 Insn::RewindAsync { cursor_id } => {
-                    let cursor = state.cursors.get_mut(cursor_id).unwrap();
+                    let cursor = cursors.get_mut(cursor_id).unwrap();
                     match cursor.rewind()? {
                         CursorResult::Ok(()) => {}
                         CursorResult::IO => {
@@ -225,7 +227,7 @@ impl Program {
                     cursor_id,
                     pc_if_empty,
                 } => {
-                    let cursor = state.cursors.get_mut(cursor_id).unwrap();
+                    let cursor = cursors.get_mut(cursor_id).unwrap();
                     cursor.wait_for_completion()?;
                     if cursor.is_empty() {
                         state.pc = *pc_if_empty;
@@ -238,7 +240,7 @@ impl Program {
                     column,
                     dest,
                 } => {
-                    let cursor = state.cursors.get_mut(cursor_id).unwrap();
+                    let cursor = cursors.get_mut(cursor_id).unwrap();
                     if let Some(ref record) = *cursor.record()? {
                         state.registers[*dest] = record.values[*column].clone();
                     } else {
@@ -252,13 +254,13 @@ impl Program {
                 } => {
                     let mut values = Vec::with_capacity(*register_end - *register_start);
                     for i in *register_start..*register_end {
-                        values.push(state.registers[i].clone());
+                        values.push(crate::types::to_value(&state.registers[i]));
                     }
                     state.pc += 1;
                     return Ok(StepResult::Row(Record::new(values)));
                 }
                 Insn::NextAsync { cursor_id } => {
-                    let cursor = state.cursors.get_mut(cursor_id).unwrap();
+                    let cursor = cursors.get_mut(cursor_id).unwrap();
                     match cursor.next()? {
                         CursorResult::Ok(_) => {}
                         CursorResult::IO => {
@@ -272,7 +274,7 @@ impl Program {
                     cursor_id,
                     pc_if_next,
                 } => {
-                    let cursor = state.cursors.get_mut(cursor_id).unwrap();
+                    let cursor = cursors.get_mut(cursor_id).unwrap();
                     cursor.wait_for_completion()?;
                     if cursor.has_record() {
                         state.pc = *pc_if_next;
@@ -290,22 +292,22 @@ impl Program {
                     state.pc = *target_pc;
                 }
                 Insn::Integer { value, dest } => {
-                    state.registers[*dest] = Value::Integer(*value);
+                    state.registers[*dest] = OwnedValue::Integer(*value);
                     state.pc += 1;
                 }
                 Insn::RowId { cursor_id, dest } => {
-                    let cursor = state.cursors.get_mut(cursor_id).unwrap();
+                    let cursor = cursors.get_mut(cursor_id).unwrap();
                     if let Some(ref rowid) = *cursor.rowid()? {
-                        state.registers[*dest] = Value::Integer(*rowid as i64);
+                        state.registers[*dest] = OwnedValue::Integer(*rowid as i64);
                     } else {
                         todo!();
                     }
                     state.pc += 1;
                 }
                 Insn::DecrJumpZero { reg, target_pc } => match state.registers[*reg] {
-                    Value::Integer(n) => {
+                    OwnedValue::Integer(n) => {
                         if n > 0 {
-                            state.registers[*reg] = Value::Integer(n - 1);
+                            state.registers[*reg] = OwnedValue::Integer(n - 1);
                             state.pc += 1;
                         } else {
                             state.pc = *target_pc;