added comments here and there

src/page.rs

@@ -15,15 +15,15 @@ pub enum PageType {
 #[derive(Debug)]
 pub struct Page {
     pagetype: PageType,
-    id: usize,
+    id: usize,           // rowid
-    start: Value,
+    start: Value,        // first value in page
-    end: Value,
+    end: Value,          // last value in page
-    data: Vec<u8>,
+    data: Vec<u8>,       // page data
-    index_pos: u16,
+    index_pos: u16,      // current write position for indexes (to the page data)
-    data_pos: u16,
+    data_pos: u16, // current write position for data (written backwards from the end of the page)
-    key: usize,
+    key: usize,    // ?
-    children: Vec<Page>,
+    children: Vec<Page>, // child pages
-    n_records: usize,
+    n_records: usize, // nr of records in the page
 }
 
 impl Page {

src/read.rs

@@ -1,7 +1,7 @@
 use crate::table::Table;
 
-use std::fs;
 use crate::record::Record;
+use std::fs;
 
 const EOL: &str = "\n";
 
@@ -31,7 +31,7 @@ impl Table {
                     //TODO quoted values
                     record.add_value(value);
                 }
-                table.add_record(record);
+                table.insert(record);
             }
         }
         table

src/record.rs

@@ -10,19 +10,24 @@ pub struct Record {
 }
 
 impl Record {
+    /// returns the length of the string representation,
+    /// for display purposes
     pub fn string_len(&self) -> usize {
         self.values.iter().map(Value::string_len).sum()
     }
 
+    /// returns the length of the internal byte representation
     pub fn bytes_len(&self) -> u16 {
         let record_length: u16 = self.values.iter().map(Value::bytes_len).sum();
         record_length + 1
     }
 
+    /// pushes a value to the record
     pub fn add_value(&mut self, value: impl Into<Value>) {
         self.values.push(value.into());
     }
 
+    /// gets the value at the column index of the record
     pub fn get(&self, index: usize) -> &Value {
         self.values.get(index).unwrap() //TODO
     }
@@ -31,6 +36,7 @@ impl Record {
 impl Add for &Record {
     type Output = Record;
 
+    /// returns a new records that is the 'join' of the two inputs
     fn add(self, rhs: Self) -> Self::Output {
         let mut sum = Record::default();
         sum.values.append(&mut self.values.clone());
@@ -40,17 +46,23 @@ impl Add for &Record {
 }
 
 impl From<Record> for Vec<u8> {
+    /// returns the byte reprsentation of the record
+    /// which will be stored physically in the page (and some day on disk)
     fn from(mut record: Record) -> Vec<u8> {
-        let record_length = record.bytes_len();
+        let record_length = record.bytes_len(); // len of all the values
-        let mut length_bytes = varint::write(u64::from(record_length));
+        let mut length_bytes = varint::write(u64::from(record_length)); // the length of the above in bytes representation
-        let mut rowid_bytes = varint::write(record.rowid);
+        let mut rowid_bytes = varint::write(record.rowid); // the bytes representation of the rowid
 
         let mut buffer =
             Vec::with_capacity(length_bytes.len() + rowid_bytes.len() + record_length as usize);
         buffer.append(&mut length_bytes);
         buffer.append(&mut rowid_bytes);
 
-        // 'The initial portion of the payload that does not spill to overflow pages.'
+        // sqlite docs: 'The initial portion of the payload that does not spill to overflow pages.'
+        // the length of the byte representation of all value types in the record
+        // -> after the record header, first all types (text, int, float etc) for the record are written
+        // after that come the values themselves
+        // so decoders first read this value to know how many types there are (how many bytes to read to decode the type bytes)
         let length_of_encoded_column_types: usize =
             record.values.iter().map(|v| v.datatype_bytes.len()).sum();
         buffer.append(&mut varint::write(
@@ -70,6 +82,10 @@ impl From<Record> for Vec<u8> {
     }
 }
 
+/// returns the Record from the byte representation
+/// tuple (len, byte buffer)
+/// len is the length that was read from the bytes before calling this
+// needs improving, for clarity get rid of the tuple
 impl Into<Record> for (u64, &[u8]) {
     fn into(self) -> Record {
         let (len, data) = self;
@@ -79,12 +95,15 @@ impl Into<Record> for (u64, &[u8]) {
         let mut datatypes = vec![];
 
         //read n of fields
-        while (offset < len) {
+
+        while offset < len {
+            //WRONG, read this len first from the buffer
             let (inc, datatype) = varint::read(&data[offset..]);
             datatypes.push(datatype);
             offset += inc;
         }
 
+        // decode the values
         let mut values: Vec<Value> = vec![];
         for dt in datatypes {
             match dt {

src/table.rs

@@ -6,27 +6,30 @@ use std::cell::RefCell;
 use std::rc::Rc;
 use std::{
     cmp::Ordering,
-    collections::{BTreeMap, HashMap}
+    collections::{BTreeMap, HashMap},
 };
 
+// work in progress
 #[derive(Debug)]
 pub struct View {
     records: BTreeMap<Key, Key>,
 }
 
+/// table struct
 #[derive(Debug)]
 pub struct Table {
     name: String,
-    cols_by_name: HashMap<String, usize>,
+    cols_by_name: HashMap<String, usize>, // map names to the internal column indexes, for fetching record values
-    pub(crate) cols: Vec<String>,
+    pub(crate) cols: Vec<String>,         // column names
-    pub(crate) root: Rc<RefCell<Page>>,
+    pub(crate) root: Rc<RefCell<Page>>,   // table root page
-    pub views: HashMap<String, View>,
+    pub views: HashMap<String, View>, // cache all internally used views // not sure about this design
-    page_ids: ThreadSafeIdGenerator,
+    page_ids: ThreadSafeIdGenerator,  // generate page ids
-    row_ids: ThreadSafeIdGenerator,
+    row_ids: ThreadSafeIdGenerator,   // generate row ids
-    current_page: Rc<RefCell<Page>>,
+    current_page: Rc<RefCell<Page>>,  // ref to current page for (bulk) loading
 }
 
 impl Table {
+    /// returns a new empty table
     pub fn new(name: impl Into<String>) -> Self {
         let root = Rc::new(RefCell::new(Page::new(PageType::Root, 0)));
         Self {
@@ -52,14 +55,20 @@ impl Table {
         result
     }
 
-    pub fn add_record(&mut self, record: Record) {
+    /// insert a new record
+    /// use: individual insert query, bulk loading
+    pub fn insert(&mut self, record: Record) {
         self.current_page.borrow_mut().insert(record);
     }
 
+    /// true if the column name is contained in the table
     pub fn has_column(&self, name: impl Into<String>) -> bool {
         self.cols_by_name.contains_key(&name.into())
     }
 
+    /// add column, for alter table
+    /// also for computing joins
+    /// allows duplicates by adding an index -> name, name => name, name2
     pub fn add_column(&mut self, name: impl Into<String>, allow_duplicates: bool) {
         let col_index = self.cols.len();
         let orig_name: String = name.into();
@@ -83,6 +92,8 @@ impl Table {
         self.cols.push(name);
     }
 
+    /// from a comma separated list of strings, return the column indexes in the record
+    /// TODO invalid names
     pub fn get_column_indexes(&self, expression: &str) -> Vec<usize> {
         expression
             .split(",")
@@ -91,16 +102,19 @@ impl Table {
     }
 
     pub fn get_index(&self, col_name: &str) -> usize {
-        *self.cols_by_name.get(col_name).unwrap()
+        *self.cols_by_name.get(col_name).unwrap() // TODO handle invalid names better
     }
 
+    // work in progress
     pub fn iter(&self) -> TableIter {
         TableIter {
-            rootPage: Rc::clone(&self.root),
+            root_page: Rc::clone(&self.root),
             index: 0,
         }
     }
 
+    /// iterate records, only returning "subrecords" -> not all columns in the records
+    /// 'select name from table'
     pub fn select_columns<'a>(&'a self, columns: &'a Vec<&'a str>) -> OwnedColIter<'a> {
         OwnedColIter {
             cols: columns,
@@ -108,6 +122,7 @@ impl Table {
         }
     }
 
+    /// iterate the column names
     pub fn iter_colums(&self) -> ColIter {
         ColIter {
             cols: &self.cols,
@@ -115,6 +130,7 @@ impl Table {
         }
     }
 
+    // work in progress
     // pub fn where_clause(&self, colindex: usize, value: &Value) -> Option<&Record> {
     //     for record in self.iter() {
     //         let r = record.get(colindex);
@@ -126,8 +142,10 @@ impl Table {
     // }
 }
 
+// iterators
+
 pub struct TableIter {
-    rootPage: Rc<RefCell<Page>>,
+    root_page: Rc<RefCell<Page>>,
     index: usize,
 }
 
@@ -135,7 +153,7 @@ impl Iterator for TableIter {
     type Item = Record;
 
     fn next(&mut self) -> Option<Self::Item> {
-        self.rootPage.borrow().get(self.index)
+        self.root_page.borrow().get(self.index)
     }
 }
 
@@ -175,6 +193,8 @@ impl<'a> Iterator for OwnedColIter<'a> {
     }
 }
 
+/// keys for indexes. Allow compound keys
+// move to separate file
 #[derive(Debug)]
 pub struct Key {
     values: Vec<Value>,

src/value.rs

@@ -1,8 +1,8 @@
 use std::{cmp::Ordering, fmt::Display};
 
+use crate::varint;
 use anyhow::anyhow;
 use byteorder::{BigEndian, ByteOrder};
-use crate::varint;
 
 #[derive(Debug, Clone, PartialEq, Eq, Ord)]
 pub struct Value {
@@ -69,12 +69,14 @@ impl Value {
         }
     }
 
+    /// get the length of the encoding of the value
     pub fn bytes_len(&self) -> u16 {
         (self.datatype_bytes.len() + self.data.len()) as u16
     }
 
+    // can this be a constant?
     pub fn null() -> Self {
-        Self::new(0 ,vec![])
+        Self::new(0, vec![])
     }
 
     pub fn from_f64(value: f64) -> Self {
@@ -92,14 +94,14 @@ impl Value {
                 (int_datatype(data.len()), data)
             }
         };
-        Self::new(datatype,data)
+        Self::new(datatype, data)
     }
 
     pub fn from_text(value: impl Into<String>) -> Self {
         let value: String = value.into();
         let datatype = (13 + value.len() * 2) as u64;
         let data = value.as_bytes().to_vec();
-        Self::new(datatype,data)
+        Self::new(datatype, data)
     }
 
     pub fn datatype(&self) -> anyhow::Result<Datatype> {

src/vm/mod.rs

@@ -3,6 +3,7 @@ use std::collections::HashMap;
 use crate::table::Table;
 use crate::value::Value;
 
+// beginnetje
 struct Vm {
     tables: HashMap<String, Table>,
     stack: Vec<Value>,