Implement full table scan

core/btree.rs

@@ -1,5 +1,5 @@
 use crate::pager::Pager;
-use crate::sqlite3_ondisk::{BTreeCell, BTreePage, TableLeafCell};
+use crate::sqlite3_ondisk::{BTreeCell, BTreePage, TableInteriorCell, TableLeafCell};
 use crate::types::Record;
 
 use anyhow::Result;
@@ -7,12 +7,36 @@ use anyhow::Result;
 use std::cell::{Ref, RefCell};
 use std::sync::Arc;
 
+pub struct MemPage {
+    parent: Option<Arc<MemPage>>,
+    page_idx: usize,
+    cell_idx: RefCell<usize>,
+}
+
+impl MemPage {
+    pub fn new(parent: Option<Arc<MemPage>>, page_idx: usize, cell_idx: usize) -> Self {
+        Self {
+            parent,
+            page_idx,
+            cell_idx: RefCell::new(cell_idx),
+        }
+    }
+
+    pub fn cell_idx(&self) -> usize {
+        *self.cell_idx.borrow()
+    }
+
+    pub fn advance(&self) {
+        let mut cell_idx = self.cell_idx.borrow_mut();
+        *cell_idx += 1;
+    }
+}
+
 pub struct Cursor {
     pager: Arc<Pager>,
     root_page: usize,
-    page: RefCell<Option<Arc<BTreePage>>>,
+    page: RefCell<Option<Arc<MemPage>>>,
     record: RefCell<Option<Record>>,
-    cell_idx: usize,
 }
 
 impl Cursor {
@@ -22,7 +46,6 @@ impl Cursor {
             root_page,
             page: RefCell::new(None),
             record: RefCell::new(None),
-            cell_idx: 0,
         }
     }
 
@@ -31,8 +54,8 @@ impl Cursor {
     }
 
     pub fn rewind(&mut self) -> Result<()> {
-        self.page
-            .replace(Some(self.pager.read_page(self.root_page)?));
+        let mem_page = MemPage::new(None, self.root_page, 0);
+        self.page.replace(Some(Arc::new(mem_page)));
         let record = self.get_next_record()?;
         self.record.replace(record);
         Ok(())
@@ -59,25 +82,41 @@ impl Cursor {
     }
 
     fn get_next_record(&mut self) -> Result<Option<Record>> {
-        match self.page.borrow_mut().as_mut() {
-            Some(page) => {
-                if self.cell_idx < page.cells.len() {
-                    let cell = &page.cells[self.cell_idx];
-                    self.cell_idx += 1;
-                    match &cell {
-                        BTreeCell::TableInteriorCell(_) => {
-                            todo!();
-                        }
-                        BTreeCell::TableLeafCell(TableLeafCell { _rowid, _payload }) => {
-                            let record = crate::sqlite3_ondisk::read_record(_payload)?;
-                            Ok(Some(record))
-                        }
+        loop {
+            let mem_page = {
+                let mem_page = self.page.borrow();
+                let mem_page = mem_page.as_ref().unwrap();
+                mem_page.clone()
+            };
+            let page_idx = mem_page.page_idx;
+            let page = self.pager.read_page(page_idx)?;
+            if mem_page.cell_idx() >= page.cells.len() {
+                match mem_page.parent {
+                    Some(ref parent) => {
+                        self.page.replace(Some(parent.clone()));
+                        continue;
                     }
-                } else {
-                    Ok(None)
+                    None => return Ok(None),
+                }
+            }
+            let cell = &page.cells[mem_page.cell_idx()];
+            match &cell {
+                BTreeCell::TableInteriorCell(TableInteriorCell {
+                    _left_child_page,
+                    _rowid,
+                }) => {
+                    mem_page.advance();
+                    let mem_page =
+                        MemPage::new(Some(mem_page.clone()), *_left_child_page as usize, 0);
+                    self.page.replace(Some(Arc::new(mem_page)));
+                    continue;
+                }
+                BTreeCell::TableLeafCell(TableLeafCell { _rowid, _payload }) => {
+                    mem_page.advance();
+                    let record = crate::sqlite3_ondisk::read_record(_payload)?;
+                    return Ok(Some(record));
                 }
             }
-            None => Ok(None),
         }
     }
 }