Implement basic schema functionality, upsert

1 files changed, 260 insertions, 21 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 6a1e1d0..72d216b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,7 +3,7 @@ extern crate log;
 pub mod log_db {
     use fs2::FileExt;
     use priority_queue::PriorityQueue;
-    use std::collections::BTreeMap;
+    use std::collections::{BTreeMap, HashSet};
     use std::fs;
     use std::io;
     use std::io::Write;
@@ -11,12 +11,105 @@ pub mod log_db {
 
     const ACTIVE_LOG_FILENAME: &str = "db";
 
-    pub trait Record {
-        fn serialize(&self) -> Vec<u8>;
-        fn deserialize(data: Vec<u8>) -> Self;
+    #[derive(Debug, Clone, Ord, PartialOrd, Eq, PartialEq)]
+    pub enum IndexableValue {
+        Int(i64),
+        String(String),
     }
 
-    pub struct Config {
+    #[derive(Debug, Clone)]
+    pub enum RecordFieldType {
+        Int,
+        Float,
+        String,
+        Bytes,
+    }
+
+    #[derive(Debug, Clone)]
+    pub enum RecordValue {
+        Null,
+        Int(i64),
+        Float(f64),
+        String(String),
+        Bytes(Vec<u8>),
+    }
+
+    impl RecordValue {
+        fn serialize(&self) -> Vec<u8> {
+            match self {
+                RecordValue::Null => {
+                    vec![0] // Tag for Null
+                }
+                RecordValue::Int(i) => {
+                    let mut bytes = vec![1]; // Tag for Int
+                    bytes.extend(&i.to_be_bytes());
+                    bytes
+                }
+                RecordValue::Float(f) => {
+                    let mut bytes = vec![2]; // Tag for Float
+                    bytes.extend(&f.to_be_bytes());
+                    bytes
+                }
+                RecordValue::String(s) => {
+                    let mut bytes = vec![3]; // Tag for String
+                    let length = s.len() as u64;
+                    bytes.extend(&length.to_be_bytes());
+                    bytes.extend(s.as_bytes());
+                    bytes
+                }
+                RecordValue::Bytes(b) => {
+                    let mut bytes = vec![3]; // Tag for Bytes
+                    let length = b.len() as u64;
+                    bytes.extend(&length.to_be_bytes());
+                    bytes.extend(b);
+                    bytes
+                }
+            }
+        }
+
+        fn deserialize(bytes: &[u8]) -> RecordValue {
+            match bytes[0] {
+                0 => RecordValue::Null,
+                1 => {
+                    let mut int_bytes = [0; 8];
+                    int_bytes.copy_from_slice(&bytes[1..9]);
+                    RecordValue::Int(i64::from_be_bytes(int_bytes))
+                }
+                2 => {
+                    let mut float_bytes = [0; 8];
+                    float_bytes.copy_from_slice(&bytes[1..9]);
+                    RecordValue::Float(f64::from_be_bytes(float_bytes))
+                }
+                3 => {
+                    let length_bytes = &bytes[1..9];
+                    let length = u64::from_be_bytes(length_bytes.try_into().unwrap()) as usize;
+                    RecordValue::String(String::from_utf8(bytes[9..9 + length].to_vec()).unwrap())
+                }
+                4 => {
+                    let length_bytes = &bytes[1..9];
+                    let length = u64::from_be_bytes(length_bytes.try_into().unwrap()) as usize;
+                    RecordValue::Bytes(bytes[9..9 + length].to_vec())
+                }
+                _ => panic!("Invalid tag"),
+            }
+        }
+
+        fn as_indexable(&self) -> Option<IndexableValue> {
+            match self {
+                RecordValue::Int(i) => Some(IndexableValue::Int(*i)),
+                RecordValue::String(s) => Some(IndexableValue::String(s.clone())),
+                _ => None,
+            }
+        }
+    }
+
+    #[derive(Debug, Clone)]
+    pub struct Record {
+        pub values: Vec<RecordValue>,
+    }
+
+    #[derive(Clone)]
+    pub struct Config<Field: Eq + Clone> {
         /// Directory where the database will store its data.
         pub data_dir: String,
         /// The maximum size of a segment file in bytes.
@@ -26,19 +119,26 @@ pub mod log_db {
         /// The maximum size of a single memtable in bytes.
         /// Note that each secondary index will have its own memtable.
         pub memtable_size: u64,
+        /// The field schema of the database.
+        pub fields: Vec<(Field, RecordFieldType)>,
+        /// The primary key of the database, used to construct
+        /// the primary memtable index. This should be the field
+        /// that is most frequently queried.
+        pub primary_key: Field,
+        /// The secondary keys of the database, used to construct
+        /// the secondary memtable indexes.
+        pub secondary_keys: Vec<Field>,
     }
 
-    pub struct DB<T: Record> {
-        data_dir: String,
-        segment_size: u64,
-        memtable_size: u64,
-
-        pub log_path: PathBuf,
-        primary_memtable: BTreeMap<u64, T>,
+    pub struct DB<Field: Eq + Clone> {
+        config: Config<Field>,
+        log_path: PathBuf,
+        primary_memtable: BTreeMap<IndexableValue, Record>,
+        secondary_memtables: Vec<BTreeMap<IndexableValue, HashSet<Record>>>,
     }
 
-    impl<T: Record> DB<T> {
-        pub fn initialize(config: &Config) -> Result<DB<T>, io::Error> {
+    impl<Field: Eq + Clone> DB<Field> {
+        pub fn initialize(config: &Config<Field>) -> Result<DB<Field>, io::Error> {
             info!("Initializing DB");
             // If data_dir does not exist, create it
             if !fs::exists(&config.data_dir)? {
@@ -47,18 +147,89 @@ pub mod log_db {
 
             let log_path = Path::new(&config.data_dir).join(ACTIVE_LOG_FILENAME);
 
-            let db = DB::<T> {
-                data_dir: config.data_dir.clone(),
-                segment_size: config.segment_size,
-                memtable_size: config.memtable_size,
+            // Create the log file if it does not exist
+            let _file = fs::OpenOptions::new()
+                .create(true)
+                .append(true)
+                .open(&log_path)?;
+
+            // Join primary key and secondary keys vec into a single vec
+            let mut all_keys = vec![&config.primary_key];
+            all_keys.extend(&config.secondary_keys);
+
+            // If any of the keys is not in the schema or
+            // is not an IndexableValue, return an error
+            for &key in &all_keys {
+                let (_, field_type) =
+                    config
+                        .fields
+                        .iter()
+                        .find(|(field, _)| field == key)
+                        .ok_or(io::Error::new(
+                            io::ErrorKind::InvalidInput,
+                            "Secondary key must be present in the field schema",
+                        ))?;
 
+                match field_type {
+                    RecordFieldType::Int | RecordFieldType::String => {}
+                    _ => {
+                        return Err(io::Error::new(
+                            io::ErrorKind::InvalidInput,
+                            "Secondary key must be an IndexableValue",
+                        ))
+                    }
+                }
+            }
+            let primary_memtable = BTreeMap::<IndexableValue, Record>::new();
+            let secondary_memtables = config
+                .secondary_keys
+                .iter()
+                .map(|_| BTreeMap::<IndexableValue, HashSet<Record>>::new())
+                .collect();
+
+            let db = DB::<Field> {
+                config: config.clone(),
                 log_path,
-                primary_memtable: BTreeMap::new(),
+                primary_memtable,
+                secondary_memtables,
             };
             Ok(db)
         }
 
-        pub fn upsert(&self, record: &T) -> Result<(), io::Error> {
+        pub fn upsert(&mut self, record: &Record) -> Result<(), io::Error> {
+            // Validate the record length
+            if record.values.len() != self.config.fields.len() {
+                return Err(io::Error::new(
+                    io::ErrorKind::InvalidInput,
+                    format!(
+                        "Record has an incorrect number of fields: {}, expected {}",
+                        record.values.len(),
+                        self.config.fields.len()
+                    ),
+                ));
+            }
+
+            // Validate that record fields match schema types
+            // TODO: handle Null
+            for (i, (_, field_type)) in self.config.fields.iter().enumerate() {
+                match (&record.values[i], field_type) {
+                    (RecordValue::Int(_), RecordFieldType::Int) => {}
+                    (RecordValue::Float(_), RecordFieldType::Float) => {}
+                    (RecordValue::String(_), RecordFieldType::String) => {}
+                    (RecordValue::Bytes(_), RecordFieldType::Bytes) => {}
+                    _ => {
+                        return Err(io::Error::new(
+                            io::ErrorKind::InvalidInput,
+                            format!(
+                                "Record field {} has incorrect type: {:?}, expected {:?}",
+                                i, record.values[i], field_type
+                            ),
+                        ))
+                    }
+                }
+            }
+
+            // Open the log file in append mode
             let mut file = fs::OpenOptions::new()
                 .create(true)
                 .append(true)
@@ -68,7 +239,13 @@ pub mod log_db {
             file.lock_exclusive()?;
 
             // Write the record to the log
-            let serialized = record.serialize();
+            // Each serialized row is suffixed with the field separator character
+            let mut serialized = record
+                .values
+                .iter()
+                .flat_map(|field| field.serialize())
+                .collect::<Vec<u8>>();
+            serialized.extend(vec![b'\x1C']);
             file.write_all(&serialized)?;
 
             // Sync to disk
@@ -77,7 +254,69 @@ pub mod log_db {
 
             file.unlock()?;
 
+            // Update the primary memtable
+            let primary_key_index = self
+                .config
+                .fields
+                .iter()
+                .position(|(field, _)| field == &self.config.primary_key)
+                .ok_or(io::Error::new(
+                    io::ErrorKind::InvalidInput,
+                    "Primary key not found in schema after initialize",
+                ))?;
+            let primary_value =
+                &record.values[primary_key_index]
+                    .as_indexable()
+                    .ok_or(io::Error::new(
+                        io::ErrorKind::InvalidInput,
+                        "Primary key must be an IndexableValue",
+                    ))?;
+
+            self.primary_memtable
+                .insert(primary_value.clone(), record.clone());
+
+            // TODO: Update secondary memtables
+
             Ok(())
         }
+
+        pub fn get(&self, field: Field, key: RecordValue) -> Result<Option<Record>, io::Error> {
+            // If the requested field is the primary key, look up the value in the primary memtable
+            if field == self.config.primary_key {
+                let primary_value = key.as_indexable().ok_or(io::Error::new(
+                    io::ErrorKind::InvalidInput,
+                    "Primary key must be an IndexableValue",
+                ))?;
+
+                let found = self.primary_memtable.get(&primary_value);
+                if let Some(record) = found {
+                    return Ok(Some(record.clone()));
+                }
+            }
+
+            // TODO: query secondary memtables
+
+            // Get the index of the requested field
+            let key_index = self
+                .config
+                .fields
+                .iter()
+                .position(|(schema_field, _)| schema_field == &field)
+                .ok_or(io::Error::new(
+                    io::ErrorKind::InvalidInput,
+                    "Key not found in schema after initialize",
+                ))?;
+
+            // Open the file and acquire a shared lock for reading
+            let file = fs::OpenOptions::new().read(true).open(&self.log_path)?;
+            file.lock_shared()?;
+
+            // Do a log file scan from the bottom up to find the record
+            // TODO
+
+            file.unlock()?;
+
+            Ok(None)
+        }
     }
 }