Add brute-force search

storage_engine/src/cursor.rs

@@ -2,17 +2,18 @@ use tokio::io::{AsyncReadExt, AsyncWriteExt, AsyncSeekExt, SeekFrom};
 use tokio::fs::{File, OpenOptions};
 use std::path::Path;
 use std::marker::PhantomData;
+use crate::error::{Error, DecodeErrorKind};
 
 use async_trait::async_trait;
 
 use bincode;
 use bincode::{Decode, Encode};
-use crate::binary_coding::encode;
+use crate::binary_coding::{encode, decode};
 
 use crate::entry::{Entry, EntryDetailed};
 use crate::entry_header::{EntryHeaderWithDataSize, EntryHeader};
 use crate::store_header::StoreHeader;
-use crate::storage_engine::{Store, FilePosition, Result, ROWS_FILE_NAME};
+use crate::storage_engine::{Store, FilePosition, Column, Result, ROWS_FILE_NAME};
 
 #[async_trait]
 // TODO: Make this private
@@ -51,6 +52,12 @@ pub trait PrimitiveCursor<T> {
         self.seek_to(StoreHeader::SIZE as u64).await
     }
 
+    // Seeks from current position by offset and returns new file position
+    async fn seek_by(&mut self, offset: i64) -> Result<FilePosition> {
+        let file_position = self.file().seek(SeekFrom::Current(offset)).await?;
+        Ok(file_position)
+    }
+
     async fn current_file_position(&mut self) -> Result<FilePosition> {
         let next_file_position: FilePosition = self.file().stream_position().await?;
         Ok(next_file_position)
@@ -59,7 +66,6 @@ pub trait PrimitiveCursor<T> {
     async fn is_at_eof(&mut self) -> Result<bool> {
         let current_file_position = self.current_file_position().await?;
         let eof_file_position = self.eof_file_position();
-        println!("IN EOF: current={}, eof_file_position={}", current_file_position, eof_file_position);
         Ok(current_file_position == eof_file_position)
     }
 }
@@ -91,18 +97,31 @@ pub trait CursorWithStoreHeader<T>: PrimitiveCursor<T> {
     }
 
     // ===Iteration===
-    // Assumes that the current file position is at a valid entry or EOF.
+    // The following functions assume that the current file position is at a valid entry or EOF.
+
+
+    // WARNING: This moves the file_position to start of the data, so you can't just call
+    //    next_entry_header() a bunch of times. You must move the cursor!
+    async fn next_entry_header(&mut self) -> Result<Option<EntryHeaderWithDataSize>> {
+        if self.is_at_eof().await? {
+            return Ok(None)
+        }
+
+        let entry_header = self.read_entry_header().await?;
+
+        Ok(Some(entry_header))
+    }
+
+    // This is meant to be used after next_entry_header() is called.
+    async fn jump_from_start_of_entry_data_to_next_entry(&mut self, entry_header: &EntryHeaderWithDataSize) -> Result<FilePosition>{
+        let file_position = self.seek_by(entry_header.size_of_data() as i64).await?;
+        Ok(file_position)
+    }
+
     async fn next(&mut self) -> Result<Option<EntryDetailed<T>>> 
         where T: Decode
     {
-        println!("are we at eof?");
-        if self.is_at_eof().await? {
-            println!("YES");
-            return Ok(None)
-        }
-        println!("NO");
-
-        let entry_header = self.read_entry_header().await?;
+        let Some(entry_header) = self.next_entry_header().await? else { return Ok(None) };
 
         let mut data_bytes: Vec<u8> = vec![0; entry_header.size_of_data()];
         self.read_bytes(&mut data_bytes).await?;
@@ -112,6 +131,59 @@ pub trait CursorWithStoreHeader<T>: PrimitiveCursor<T> {
         Ok(Some(entry))
     }
 
+    // Like next, but only reads the column, not the whole entry. 
+    async fn next_at_column(&mut self, column: Column) -> Result<Option<(EntryHeaderWithDataSize, T)>> 
+        where T: Decode + Send
+    {
+        let Some(entry_header) = self.next_entry_header().await? else { return Ok(None) };
+        let file_position_at_start_of_data = self.current_file_position().await?;
+
+        // figuring out how much to decode
+        let column_offset = entry_header.offset_of_column(column);
+        self.seek_by(column_offset as i64).await?;
+
+        // reading and decoding
+        let mut bytes: Vec<u8> = vec![0; entry_header.data_sizes[column as usize]];
+        self.read_bytes(&mut bytes).await?;
+        let (value, _) =
+            decode::<T>(&bytes[..])
+                .map_err(|e| Error::DecodeError(DecodeErrorKind::EntryIsDeleted, e))?;
+
+        // jumping to next entry
+        self.seek_to(file_position_at_start_of_data).await?;
+        self.jump_from_start_of_entry_data_to_next_entry(&entry_header).await?;
+
+        Ok(Some((entry_header, value)))
+    }
+
+    async fn next_alive(&mut self) -> Result<Option<EntryDetailed<T>>> 
+        where T: Decode
+    {
+        while let Some(entry) = self.next().await? {
+            if !entry.header.is_deleted  {
+                return Ok(Some(entry))
+            }
+        }
+        Ok(None)
+    }
+
+    // ===Search===
+    async fn find_first_eq_bruteforce(&mut self, column: Column, t0: &T) -> Result<Option<EntryDetailed<T>>> 
+        where T: Decode + PartialEq + Send + Sync
+    {
+        let mut file_position = self.current_file_position().await?;
+        while let Some((_, t)) = self.next_at_column(column).await? {
+            if &t == t0  {
+                // go back and decode the whole entry
+                self.seek_to(file_position).await?;
+                return self.next().await
+            } else {
+                file_position = self.current_file_position().await?;
+            }
+        }
+        Ok(None)
+    }
+
     // ===Debugging===
     async fn read_entries(&mut self) -> Result<()> 
         where T: Decode + std::fmt::Debug
@@ -301,14 +373,10 @@ impl <'cursor, T> WriteCursor<'cursor, T> {
         where T: Send
     {
         self.seek_to(file_position).await?;
-        println!("Attempting to read the entry");
         let mut entry_header = self.read_entry_header().await?;
-        println!("Entry Header == {:?}", entry_header);
         if entry_header.is_deleted {
-            println!("Already deleted");
             Ok(())
         } else {
-            println!("Marking as deleted");
             self.increment_deleted_count().await?;
             self.seek_to(file_position).await?;
 

storage_engine/src/entry.rs

@@ -13,8 +13,8 @@ pub struct Entry<T> {
 
 #[derive(Debug)]
 pub struct EntryDetailed<T> {
-    header: EntryHeaderWithDataSize,
-    data: Vec<T>,
+    pub header: EntryHeaderWithDataSize,
+    pub data: Vec<T>,
 }
 
 impl <T>Entry<T> {

storage_engine/src/entry_header.rs

@@ -1,5 +1,5 @@
 use crate::binary_coding::{decode, encode, decode_sequence};
-use crate::storage_engine::Result;
+use crate::storage_engine::{Result, Column};
 use crate::error::{Error, DecodeErrorKind};
 use std::mem::size_of;
 
@@ -42,6 +42,18 @@ impl EntryHeaderWithDataSize {
         self.data_sizes.iter().sum()
     }
 
+    pub fn offset_of_column(&self, column: Column) -> usize {
+        let mut sum = 0;
+        for (i, size) in self.data_sizes.iter().enumerate() {
+            if i < column as usize {
+                sum += size;
+            } else {
+                break
+            }
+        }
+        sum
+    }
+
     pub fn decode(bytes: &mut [u8], number_of_columns: usize) -> Result<Self> {
         let (is_deleted, _) =
             decode::<bool>(&bytes)

storage_engine/src/main.rs

@@ -108,20 +108,44 @@ async fn main() -> Result<()> {
     // println!("{:?}", store);
     // println!("{:?}", store.read_all_bytes().await?);
 
+    {
         let mut cursor = store.read_cursor().await.map_err(|e| e.to_io_or_panic())?;
-
-    // let x = cursor.next().await.map_err(|e| e.to_io_or_panic())?;
-    // println!("{:?}", x);
-    // let x = cursor.next().await.map_err(|e| e.to_io_or_panic())?;
-    // println!("{:?}", x);
-    // let x = cursor.next().await.map_err(|e| e.to_io_or_panic())?;
-    // println!("{:?}", x);
-    // let x = cursor.next().await.map_err(|e| e.to_io_or_panic())?;
-    // println!("{:?}", x);
-    // let x = cursor.next().await.map_err(|e| e.to_io_or_panic())?;
-    // println!("{:?}", x);
-
         cursor.read_entries().await.map_err(|e| e.to_io_or_panic())?;
+        // let x = cursor.next().await.map_err(|e| e.to_io_or_panic())?;
+        // println!("{:?}", x);
+        // let x = cursor.next().await.map_err(|e| e.to_io_or_panic())?;
+        // println!("{:?}", x);
+        // let x = cursor.next().await.map_err(|e| e.to_io_or_panic())?;
+        // println!("{:?}", x);
+        // let x = cursor.next().await.map_err(|e| e.to_io_or_panic())?;
+        // println!("{:?}", x);
+        // let x = cursor.next().await.map_err(|e| e.to_io_or_panic())?;
+        // println!("{:?}", x);
+    }
+
+    {
+        let mut cursor = store.read_cursor().await.map_err(|e| e.to_io_or_panic())?;
+        let column = 2;
+        let x = cursor.next_at_column(column).await.map_err(|e| e.to_io_or_panic())?;
+        println!("{:?}", x);
+        let x = cursor.next_at_column(column).await.map_err(|e| e.to_io_or_panic())?;
+        println!("{:?}", x);
+        let x = cursor.next_at_column(column).await.map_err(|e| e.to_io_or_panic())?;
+        println!("{:?}", x);
+        let x = cursor.next_at_column(column).await.map_err(|e| e.to_io_or_panic())?;
+        println!("{:?}", x);
+        let x = cursor.next_at_column(column).await.map_err(|e| e.to_io_or_panic())?;
+        println!("{:?}", x);
+    }
+
+    {
+        let mut cursor = store.read_cursor().await.map_err(|e| e.to_io_or_panic())?;
+        let column = 3;
+        let t0 = 6;
+        let x = cursor.find_first_eq_bruteforce(column, &t0).await.map_err(|e| e.to_io_or_panic())?;
+        println!("{:?}", x);
+    }
+