From 3a6fee6fe08afc0551d3325a4ef71ef5626befe6 Mon Sep 17 00:00:00 2001
From: Ziyang Hu <hu.ziyang@cantab.net>
Date: Thu, 28 Apr 2022 16:54:46 +0800
Subject: [PATCH] zero copying

---
 src/db/engine.rs       |  8 ++++----
 src/db/eval.rs         | 24 +++++++++++-------------
 src/relation/typing.rs |  2 +-
 3 files changed, 16 insertions(+), 18 deletions(-)

diff --git a/src/db/engine.rs b/src/db/engine.rs
index ef4c6707..de01004f 100644
--- a/src/db/engine.rs
+++ b/src/db/engine.rs
@@ -116,19 +116,19 @@ impl Engine {
     }
 }
 
-pub struct Session<'a> {
+pub struct Session<'a, 'b> {
     pub engine: &'a Engine,
     pub stack_depth: i32,
     pub handle: Arc<RwLock<SessionHandle>>,
     pub txn: TransactionPtr,
     pub perm_cf: SharedPtr<ColumnFamilyHandle>,
     pub temp_cf: SharedPtr<ColumnFamilyHandle>,
-    pub params: BTreeMap<String, String>,
+    pub params: BTreeMap<String, &'b str>,
 }
 // every session has its own column family to play with
 // metadata are stored in table 0
 
-impl<'a> Session<'a> {
+impl<'a, 'b> Session<'a, 'b> {
     pub fn start(&mut self) -> Result<()> {
         self.perm_cf = self.engine.db.default_cf();
         assert!(!self.perm_cf.is_null());
@@ -173,7 +173,7 @@ impl<'a> Session<'a> {
     }
 }
 
-impl<'a> Drop for Session<'a> {
+impl<'a, 't> Drop for Session<'a, 't> {
     fn drop(&mut self) {
         if let Err(e) = self.finish_work() {
             eprintln!("Dropping session failed {:?}", e);
diff --git a/src/db/eval.rs b/src/db/eval.rs
index 98022753..2e13374c 100644
--- a/src/db/eval.rs
+++ b/src/db/eval.rs
@@ -16,12 +16,12 @@ use crate::parser::{Parser, Rule};
 use crate::parser::text_identifier::build_name_in_def;
 use crate::relation::value;
 
-pub trait Environment<T: AsRef<[u8]>> where Self: Sized {
+pub trait Environment<'t, T: AsRef<[u8]>> where Self: Sized {
     fn get_next_storage_id(&mut self, in_root: bool) -> Result<u32>;
     fn get_stack_depth(&self) -> i32;
     fn push_env(&mut self);
     fn pop_env(&mut self) -> Result<()>;
-    fn set_param(&mut self, name: &str, val: String);
+    fn set_param(&mut self, name: &str, val: &'t str);
     fn define_variable(&mut self, name: &str, val: &Value, in_root: bool) -> Result<()> {
         let mut data = Tuple::with_data_prefix(DataKind::Value);
         data.push_value(val);
@@ -664,20 +664,20 @@ pub trait Environment<T: AsRef<[u8]>> where Self: Sized {
 }
 
 
-pub struct MemoryEnv {
+pub struct MemoryEnv<'a> {
     root: BTreeMap<String, OwnTuple>,
     stack: Vec<BTreeMap<String, OwnTuple>>,
-    params: BTreeMap<String, String>,
+    params: BTreeMap<String, &'a str>,
     max_storage_id: u32,
 }
 
-impl Default for MemoryEnv {
+impl <'a> Default for MemoryEnv<'a> {
     fn default() -> Self {
         MemoryEnv { root: BTreeMap::default(), stack: vec![BTreeMap::default()], max_storage_id: 0, params: BTreeMap::default() }
     }
 }
 
-impl Environment<Vec<u8>> for MemoryEnv {
+impl <'t> Environment<'t, Vec<u8>> for MemoryEnv<'t> {
     fn get_next_storage_id(&mut self, _in_root: bool) -> Result<u32> {
         self.max_storage_id += 1;
         Ok(self.max_storage_id)
@@ -698,7 +698,7 @@ impl Environment<Vec<u8>> for MemoryEnv {
         Ok(())
     }
 
-    fn set_param(&mut self, name: &str, val: String) {
+    fn set_param(&mut self, name: &str, val: &'t str) {
         self.params.insert(name.to_string(), val);
     }
 
@@ -714,7 +714,7 @@ impl Environment<Vec<u8>> for MemoryEnv {
     fn resolve_param(&self, name: &str) -> Result<Value> {
         let text = self.params.get(name).ok_or_else(|| CozoError::UndefinedParam(name.to_string()))?;
         let pair = Parser::parse(Rule::expr, text)?.next().unwrap();
-        Ok(Value::from_pair(pair)?)
+        Value::from_pair(pair)
     }
 
     fn delete_defined(&mut self, name: &str, in_root: bool) -> Result<()> {
@@ -742,7 +742,7 @@ impl Environment<Vec<u8>> for MemoryEnv {
 }
 
 
-impl<'a> Environment<SlicePtr> for Session<'a> {
+impl<'a, 't> Environment<'t, SlicePtr> for Session<'a, 't> {
     fn get_next_storage_id(&mut self, in_root: bool) -> Result<u32> {
         // TODO: deal with wrapping problem
         let mut key_entry = Tuple::with_null_prefix();
@@ -805,7 +805,7 @@ impl<'a> Environment<SlicePtr> for Session<'a> {
         Ok(())
     }
 
-    fn set_param(&mut self, name: &str, val: String) {
+    fn set_param(&mut self, name: &str, val: &'t str) {
         self.params.insert(name.to_string(), val);
     }
 
@@ -828,7 +828,7 @@ impl<'a> Environment<SlicePtr> for Session<'a> {
     fn resolve_param(&self, name: &str) -> Result<Value> {
         let text = self.params.get(name).ok_or_else(|| CozoError::UndefinedParam(name.to_string()))?;
         let pair = Parser::parse(Rule::expr, text)?.next().unwrap();
-        Ok(Value::from_pair(pair)?)
+        Value::from_pair(pair)
     }
 
     fn delete_defined(&mut self, name: &str, in_root: bool) -> Result<()> {
@@ -870,8 +870,6 @@ impl<'a> Environment<SlicePtr> for Session<'a> {
 }
 
 
-impl<'a> Session<'a> {}
-
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/src/relation/typing.rs b/src/relation/typing.rs
index 9e5d1118..b82f4e63 100644
--- a/src/relation/typing.rs
+++ b/src/relation/typing.rs
@@ -67,7 +67,7 @@ impl Typing {
 }
 
 impl Typing {
-    pub fn from_pair<T: AsRef<[u8]>, E: Environment<T>>(pair: Pair<Rule>, env: Option<&E>) -> Result<Self> {
+    pub fn from_pair<'t, T: AsRef<[u8]>, E: Environment<'t, T>>(pair: Pair<Rule>, env: Option<&E>) -> Result<Self> {
         Ok(match pair.as_rule() {
             Rule::simple_type => match pair.as_str() {
                 "Any" => Typing::Any,