Sketch out indexes in Store

storage_engine/src/cursor.rs

@@ -14,10 +14,14 @@ use crate::entry::{Entry, EntryDetailed};
 use crate::entry_header::{EntryHeaderWithDataSize, EntryHeader};
 use crate::store_header::StoreHeader;
 use crate::storage_engine::{Store, FilePosition, Column, Result, ROWS_FILE_NAME, GARBAGE_COLLECTION_INTERMEDIATE_ROWS_FILE_NAME};
+use crate::index::Index;
+
+
 
 // ===Concrete Cursors===
-pub struct ReadCursor<T> {
+pub struct ReadCursor<'a, T> {
     header: StoreHeader,
+    indexes: Vec<Option<&'a Index<T, FilePosition>>>,
     file: File,
     data_type: PhantomData<T>,
 
@@ -26,6 +30,7 @@ pub struct ReadCursor<T> {
 
 pub struct WriteCursor<'a, T> {
     header: &'a mut StoreHeader,
+    indexes: Vec<Option<&'a Index<T, FilePosition>>>,
     file: File,
     data_type: PhantomData<T>,
 
@@ -224,9 +229,20 @@ pub trait CursorWithStoreHeader<T>: PrimitiveCursor<T> {
     }
 }
 
+#[async_trait]
+pub trait CursorWithAccessToIndex<T>: CursorWithStoreHeader<T> {
+    fn indexes(&mut self) -> &[Option<&Index<T, FilePosition>>];
+
+    async fn find_in_index(&mut self, k: &T) -> Result<Option<FilePosition>> 
+        where T: Encode + Decode + Ord + Send + Sync
+    {
+        // let x = self.primary_index().lookup(k).await?;
+        todo!()
+    }
+}
 
 // ===PrimitiveCursor===
-impl <T>PrimitiveCursor<T> for ReadCursor<T> {
+impl <T>PrimitiveCursor<T> for ReadCursor<'_, T> {
     fn file(&mut self) -> &mut File {
         &mut self.file
     }
@@ -247,7 +263,7 @@ impl <T>PrimitiveCursor<T> for WriteCursor<'_, T> {
 }
 
 // ===CursorWithStoreHeader===
-impl <T>CursorWithStoreHeader<T> for ReadCursor<T> {
+impl <T>CursorWithStoreHeader<T> for ReadCursor<'_, T> {
     fn header(&self) -> &StoreHeader {
         &self.header
     }
@@ -259,9 +275,23 @@ impl <T>CursorWithStoreHeader<T> for WriteCursor<'_, T> {
     }
 }
 
-impl <T> ReadCursor<T> {
-    pub async fn new(store: &Store<T>) -> Result<Self> 
-        where T: Send
+// ===CursorWithAccessToIndex===
+impl <T>CursorWithAccessToIndex<T> for ReadCursor<'_, T> {
+    fn indexes(&mut self) -> &[Option<&Index<T, FilePosition>>] {
+        &self.indexes
+    }
+}
+
+impl <T>CursorWithAccessToIndex<T> for WriteCursor<'_, T> {
+    fn indexes(&mut self) -> &[Option<&Index<T, FilePosition>>] {
+        &self.indexes
+    }
+}
+
+
+impl <'cursor, T> ReadCursor<'cursor, T> {
+    pub async fn new<'store: 'cursor>(store: &'store Store<T>) -> Result<Self> 
+        where T: Send + Sync
     {
             let path_to_rows = Path::new(&store.header.table_folder).join(ROWS_FILE_NAME);
             let file: File =
@@ -274,6 +304,7 @@ impl <T> ReadCursor<T> {
                 header: store.header.clone(),
                 file,
                 data_type: store.data_type,
+                indexes: todo!(),
 
                 eof_file_position: 0,
             };
@@ -284,13 +315,12 @@ impl <T> ReadCursor<T> {
 
             Ok(cursor)
     }
-
-    pub async fn less_than_eq(&mut self, file_position0: FilePosition, file_position1: FilePosition) -> Result<bool> {
-        todo!()
-    }
 }
 
-impl <'cursor, T> WriteCursor<'cursor, T> {
+impl <'cursor, T> WriteCursor<'cursor, T> 
+// TODO: Consider adding this manually to wher eit is really needed
+    where T: Sync
+{
     // 'store lives atleast as long as 'cursor
     pub async fn new<'store: 'cursor>(store: &'store mut Store<T>) -> Result<Self> 
         where T: Send
@@ -307,6 +337,7 @@ impl <'cursor, T> WriteCursor<'cursor, T> {
                 header: &mut store.header,
                 file,
                 data_type: store.data_type,
+                indexes: todo!(),
 
                 eof_file_position: 0,
             };
@@ -332,6 +363,7 @@ impl <'cursor, T> WriteCursor<'cursor, T> {
                 header,
                 file,
                 data_type: PhantomData::<T>,
+                indexes: todo!(),
 
                 eof_file_position: 0,
             };
@@ -478,4 +510,20 @@ impl <'cursor, T> WriteCursor<'cursor, T> {
         // Afterwards we swap the files, and delete the garbage.
         todo!()
     }
+
+    // ===Indexing===
+    async fn insert_to_index(&mut self, t: T, file_position: FilePosition) -> Result<Option<FilePosition>> 
+        where T: Encode + Decode + Ord + Send + Sync
+    {
+        // let x = self.primary_index.insert(t, file_position).await?;
+        todo!()
+    }
+
+    async fn delete_from_index(&mut self, t: T, file_position: FilePosition) -> Result<Option<FilePosition>> 
+        where T: Encode + Decode + Ord + Send + Sync
+    {
+        // let x = self.primary_index.delete(t, file_position).await?;
+        todo!()
+    }
 }
+

storage_engine/src/index.rs

@@ -83,8 +83,8 @@ where
         Ok(())
     }
 
-    pub async fn lookup(&self, k: K) -> Result<Option<HashSet<V>>> {
-        let hashset = self.data.get(&k).unwrap();
+    pub async fn lookup(&self, k: &K) -> Result<Option<HashSet<V>>> {
+        let hashset = self.data.get(k).unwrap();
         Ok(Some(hashset.clone()))
     }
 

storage_engine/src/main.rs

@@ -52,7 +52,7 @@ async fn append_entry(cursor: &mut WriteCursor<'_, Data>, entry: &Entry<Data>) -
     Ok(file_position)
 }
 
-async fn read_entry(cursor: &mut ReadCursor<Data>, file_position: FilePosition) -> Result<Option<EntryDetailed<Data>>> {
+async fn read_entry(cursor: &mut ReadCursor<'_, Data>, file_position: FilePosition) -> Result<Option<EntryDetailed<Data>>> {
     println!("READING ENTRY at file_position={}", file_position);
     // let entry = cursor.read_entry_at(file_position).await.map_err(|e| e.to_io_or_panic())?;
     // println!("ENTRY: {:?}", entry);

storage_engine/src/storage_engine.rs

@@ -3,15 +3,12 @@ use tokio::fs::{File, OpenOptions, DirBuilder};
 use tokio::fs;
 use std::path::{Path, PathBuf};
 use std::marker::PhantomData;
-use async_trait::async_trait;
+use bincode::{Decode, Encode};
 
-use crate::index::SomethingSupportingLeq;
 use crate::error::Error;
 use crate::cursor::{ReadCursor, WriteCursor, CursorWithStoreHeader};
 use crate::store_header::StoreHeader;
-
-// TODO
-// use crate::index::Index;
+use crate::index::Index;
 
 
 pub type Result<T> = std::result::Result<T, Error>;
@@ -37,6 +34,7 @@ pub struct Store<T> {
     // All 
     pub header: StoreHeader,
     pub data_type: PhantomData<T>,
+    pub primary_index: Index<T, FilePosition>,
 }
 
 pub type PositionOfValue = FilePosition;
@@ -48,16 +46,14 @@ pub async fn store_exists(table_folder: &str) -> Result<bool> {
     Ok(fs::metadata(table_folder).await.is_ok())
 }
 
-pub async fn less_than_eq<T>(store: &mut Store<T>, file_position0: FilePosition, file_position1: FilePosition) -> Result<bool> {
-    todo!()
-}
-
 pub const ROWS_FILE_NAME: &'static str = "rows";
 pub const GARBAGE_COLLECTION_INTERMEDIATE_ROWS_FILE_NAME: &'static str = "rows_intermediate";
 
 impl <T>Store<T> {
     // ===Creation===
-    pub async fn new(table_folder: &str, number_of_columns: usize, primary_column: Column) -> Result<Self> {
+    pub async fn new(table_folder: &str, number_of_columns: usize, primary_column: Column) -> Result<Self> 
+        where T: Encode + Decode + Ord
+    {
         let path_to_table = Path::new(table_folder);
         let path_to_rows = path_to_table.join(ROWS_FILE_NAME);
         DirBuilder::new()
@@ -74,14 +70,14 @@ impl <T>Store<T> {
         // We don't need the file right now. Only cursors will later open it.
         Self::create_empty_rows_file(path_to_rows, &header).await?;
 
-        // TODO: indexes
-        // let index: Index<PositionOfValue, PositionOfRow> = Index::new(
-        //     &format!("rows_{}", primary_column.to_string()),
-        // ).await?;
+        let primary_index: Index<T, FilePosition> = Index::new(
+            &format!("rows_{}", primary_column.to_string()),
+        ).await?;
 
         let store = Self {
             header,
             data_type: PhantomData::<T>,
+            primary_index,
         };
 
         Ok(store)
@@ -103,7 +99,7 @@ impl <T>Store<T> {
     }
 
     pub async fn connect(table_folder: &str) -> Result<Self> 
-        where T: std::fmt::Debug
+        where T: std::fmt::Debug + Encode + Decode + Ord
     {
         let path_to_table = Path::new(table_folder);
         let path_to_rows = path_to_table.join(ROWS_FILE_NAME);
@@ -121,29 +117,35 @@ impl <T>Store<T> {
         file.read_exact(&mut header_bytes).await?;
         let header = StoreHeader::decode(table_folder, &mut header_bytes).await?;
 
+
+        let primary_index: Index<T, FilePosition> = Index::connect(
+            &format!("rows_{}", header.primary_column.to_string()),
+        ).await?;
+
         let store = Self {
             header,
             data_type: PhantomData::<T>,
+            primary_index
         };
         Ok(store)
     }
 
     // ===Cursors===
     pub async fn read_cursor(&self) -> Result<ReadCursor<T>> 
-        where T: Send
+        where T: Send + Sync
     {
         ReadCursor::new(self).await
     }
 
     pub async fn write_cursor(&mut self) -> Result<WriteCursor<T>> 
-        where T: Send
+        where T: Send + Sync
     {
         WriteCursor::new(self).await
     }
 
     // For debugging.
     pub async fn read_all_bytes(&mut self) -> std::result::Result<Vec<u8>, std::io::Error>
-        where T: Send
+        where T: Send + Sync
     {
         let mut cursor = self.read_cursor().await.map_err(|e| e.to_io_or_panic())?;
         let bytes = cursor.read_all_bytes().await?;