Use copy-on-write semantics for document values

Instead of blindly cloning document values (even if we don't need to mutate them), we now use copy-on-write semantics to only create a copy if we need to update a document value. This improves performance, especially when selecting documents.

src/dbs/iterator.rs

@@ -178,7 +178,7 @@ impl<'a> Iterator<'a> {
 			return;
 		}
 		// Setup a new document
-		let mut doc = Document::new(thg, val);
+		let mut doc = Document::new(thg, &val);
 
 		// Process the document
 		let res = match self.stmt {

src/doc/admit.rs

@@ -5,7 +5,7 @@ use crate::dbs::Statement;
 use crate::doc::Document;
 use crate::err::Error;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn admit(
 		&self,
 		_ctx: &Runtime,
@@ -17,19 +17,19 @@ impl Document {
 			Some(_) => Ok(()),
 			None => match stm {
 				Statement::Create(_) => Err(Error::CreateStatementError {
-					value: self.initial.clone(),
+					value: (*self.initial).clone(),
 				}),
 				Statement::Update(_) => Err(Error::UpdateStatementError {
-					value: self.initial.clone(),
+					value: (*self.initial).clone(),
 				}),
 				Statement::Relate(_) => Err(Error::RelateStatementError {
-					value: self.initial.clone(),
+					value: (*self.initial).clone(),
 				}),
 				Statement::Delete(_) => Err(Error::DeleteStatementError {
-					value: self.initial.clone(),
+					value: (*self.initial).clone(),
 				}),
 				Statement::Insert(_) => Err(Error::InsertStatementError {
-					value: self.initial.clone(),
+					value: (*self.initial).clone(),
 				}),
 				_ => unreachable!(),
 			},

src/doc/allow.rs

@@ -5,7 +5,7 @@ use crate::dbs::Statement;
 use crate::doc::Document;
 use crate::err::Error;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn allow(
 		&self,
 		_ctx: &Runtime,

src/doc/check.rs

@@ -5,7 +5,7 @@ use crate::dbs::Statement;
 use crate::doc::Document;
 use crate::err::Error;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn check(
 		&self,
 		ctx: &Runtime,

src/doc/compute.rs

@@ -6,7 +6,7 @@ use crate::doc::Document;
 use crate::err::Error;
 use crate::sql::value::Value;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn compute(
 		&mut self,
 		ctx: &Runtime,

src/doc/create.rs

@@ -6,7 +6,7 @@ use crate::doc::Document;
 use crate::err::Error;
 use crate::sql::value::Value;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn create(
 		&mut self,
 		ctx: &Runtime,

src/doc/delete.rs

@@ -6,7 +6,7 @@ use crate::doc::Document;
 use crate::err::Error;
 use crate::sql::value::Value;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn delete(
 		&mut self,
 		ctx: &Runtime,

src/doc/document.rs

@@ -1,19 +1,20 @@
 use crate::sql::thing::Thing;
 use crate::sql::value::Value;
+use std::borrow::Cow;
 
 #[derive(Clone, Debug, Default, Eq, PartialEq)]
-pub struct Document {
+pub struct Document<'a> {
 	pub(super) id: Option<Thing>,
-	pub(super) current: Value,
+	pub(super) current: Cow<'a, Value>,
-	pub(super) initial: Value,
+	pub(super) initial: Cow<'a, Value>,
 }
 
-impl Document {
+impl<'a> Document<'a> {
-	pub fn new(id: Option<Thing>, val: Value) -> Document {
+	pub fn new(id: Option<Thing>, val: &'a Value) -> Self {
 		Document {
 			id,
-			current: val.clone(),
+			current: Cow::Borrowed(val),
-			initial: val,
+			initial: Cow::Borrowed(val),
 		}
 	}
 }

src/doc/empty.rs

@@ -4,9 +4,8 @@ use crate::dbs::Runtime;
 use crate::dbs::Statement;
 use crate::doc::Document;
 use crate::err::Error;
-use crate::sql::value::Value;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn empty(
 		&self,
 		_ctx: &Runtime,
@@ -14,7 +13,7 @@ impl Document {
 		_exe: &Executor<'_>,
 		_stm: &Statement<'_>,
 	) -> Result<(), Error> {
-		match self.id.is_some() && self.current == Value::None {
+		match self.id.is_some() && self.current.is_none() {
 			true => Err(Error::IgnoreError),
 			false => Ok(()),
 		}

src/doc/erase.rs

@@ -5,7 +5,7 @@ use crate::dbs::Statement;
 use crate::doc::Document;
 use crate::err::Error;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn erase(
 		&mut self,
 		ctx: &Runtime,
@@ -13,6 +13,6 @@ impl Document {
 		exe: &Executor<'_>,
 		_stm: &Statement<'_>,
 	) -> Result<(), Error> {
-		self.current.clear(ctx, opt, exe).await
+		self.current.to_mut().clear(ctx, opt, exe).await
 	}
 }

src/doc/event.rs

@@ -5,7 +5,7 @@ use crate::dbs::Statement;
 use crate::doc::Document;
 use crate::err::Error;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn event(
 		&self,
 		_ctx: &Runtime,

src/doc/index.rs

@@ -5,7 +5,7 @@ use crate::dbs::Statement;
 use crate::doc::Document;
 use crate::err::Error;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn index(
 		&self,
 		_ctx: &Runtime,

src/doc/insert.rs

@@ -6,7 +6,7 @@ use crate::doc::Document;
 use crate::err::Error;
 use crate::sql::value::Value;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn insert(
 		&mut self,
 		_ctx: &Runtime,

src/doc/lives.rs

@@ -5,7 +5,7 @@ use crate::dbs::Statement;
 use crate::doc::Document;
 use crate::err::Error;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn lives(
 		&self,
 		_ctx: &Runtime,

src/doc/merge.rs

@@ -8,7 +8,7 @@ use crate::sql::data::Data;
 use crate::sql::operator::Operator;
 use crate::sql::value::Value;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn merge(
 		&mut self,
 		ctx: &Runtime,
@@ -25,7 +25,7 @@ impl Document {
 			_ => unreachable!(),
 		};
 		// Set default field values
-		self.current.def(ctx, opt, exe, id).await?;
+		self.current.to_mut().def(ctx, opt, exe, id).await?;
 		// Check for a data clause
 		match data {
 			// The statement has a data clause
@@ -35,26 +35,36 @@ impl Document {
 						let v = x.2.compute(ctx, opt, exe, Some(&self.current)).await?;
 						match x.1 {
 							Operator::Equal => match v {
-								Value::Void => self.current.del(ctx, opt, exe, &x.0).await?,
+								Value::Void => {
-								_ => self.current.set(ctx, opt, exe, &x.0, v).await?,
+									self.current.to_mut().del(ctx, opt, exe, &x.0).await?
+								}
+								_ => self.current.to_mut().set(ctx, opt, exe, &x.0, v).await?,
 							},
-							Operator::Inc => self.current.increment(ctx, opt, exe, &x.0, v).await?,
+							Operator::Inc => {
-							Operator::Dec => self.current.decrement(ctx, opt, exe, &x.0, v).await?,
+								self.current.to_mut().increment(ctx, opt, exe, &x.0, v).await?
+							}
+							Operator::Dec => {
+								self.current.to_mut().decrement(ctx, opt, exe, &x.0, v).await?
+							}
 							_ => unreachable!(),
 						}
 					}
 				}
-				Data::PatchExpression(v) => self.current.patch(ctx, opt, exe, v).await?,
+				Data::PatchExpression(v) => self.current.to_mut().patch(ctx, opt, exe, v).await?,
-				Data::MergeExpression(v) => self.current.merge(ctx, opt, exe, v).await?,
+				Data::MergeExpression(v) => self.current.to_mut().merge(ctx, opt, exe, v).await?,
-				Data::ReplaceExpression(v) => self.current.replace(ctx, opt, exe, v).await?,
+				Data::ReplaceExpression(v) => {
-				Data::ContentExpression(v) => self.current.replace(ctx, opt, exe, v).await?,
+					self.current.to_mut().replace(ctx, opt, exe, v).await?
+				}
+				Data::ContentExpression(v) => {
+					self.current.to_mut().replace(ctx, opt, exe, v).await?
+				}
 				_ => unreachable!(),
 			},
 			// No data clause has been set
 			None => (),
 		};
 		// Set default field values
-		self.current.def(ctx, opt, exe, id).await?;
+		self.current.to_mut().def(ctx, opt, exe, id).await?;
 		// Set ASSERT and VALUE clauses
 		// todo!();
 		// Delete non-defined FIELDs

src/doc/pluck.rs

@@ -9,7 +9,7 @@ use crate::sql::idiom::Idiom;
 use crate::sql::output::Output;
 use crate::sql::value::Value;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn pluck(
 		&self,
 		ctx: &Runtime,

src/doc/relate.rs

@@ -6,7 +6,7 @@ use crate::doc::Document;
 use crate::err::Error;
 use crate::sql::value::Value;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn relate(
 		&mut self,
 		ctx: &Runtime,

src/doc/select.rs

@@ -6,7 +6,7 @@ use crate::doc::Document;
 use crate::err::Error;
 use crate::sql::value::Value;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn select(
 		&self,
 		ctx: &Runtime,

src/doc/store.rs

@@ -5,7 +5,7 @@ use crate::dbs::Statement;
 use crate::doc::Document;
 use crate::err::Error;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn store(
 		&self,
 		_ctx: &Runtime,

src/doc/table.rs

@@ -5,7 +5,7 @@ use crate::dbs::Statement;
 use crate::doc::Document;
 use crate::err::Error;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn table(
 		&self,
 		_ctx: &Runtime,

src/doc/update.rs

@@ -6,7 +6,7 @@ use crate::doc::Document;
 use crate::err::Error;
 use crate::sql::value::Value;
 
-impl Document {
+impl<'a> Document<'a> {
 	pub async fn update(
 		&mut self,
 		ctx: &Runtime,