fix Minimum cell size must not be less than 4

Author: meteorgan

core/storage/btree.rs

@@ -6332,7 +6332,11 @@ fn compute_free_space(page: &PageContent, usable_space: u16) -> u16 {
 
 /// Allocate space for a cell on a page.
 fn allocate_cell_space(page_ref: &PageContent, amount: u16, usable_space: u16) -> Result<u16> {
-    let amount = amount as usize;
+    let mut amount = amount as usize;
+    // the minimum cell size is 4 bytes, so we need to ensure that we allocate at least that much space.
+    if amount < 4 {
+        amount = 4;
+    }
 
     let (cell_offset, _) = page_ref.cell_pointer_array_offset_and_size();
     let gap = cell_offset + 2 * page_ref.cell_count();

core/storage/sqlite3_ondisk.rs

@@ -668,7 +668,11 @@ impl PageContent {
                 if overflows {
                     to_read + n_payload
                 } else {
-                    len_payload as usize + n_payload
+                    let mut size = len_payload as usize + n_payload;
+                    if size < 4 {
+                        size = 4;
+                    }
+                    size
                 }
             }
             PageType::TableLeaf => {
@@ -683,7 +687,11 @@ impl PageContent {
                 if overflows {
                     to_read + n_payload + n_rowid
                 } else {
-                    len_payload as usize + n_payload + n_rowid
+                    let mut size = len_payload as usize + n_payload + n_rowid;
+                    if size < 4 {
+                        size = 4;
+                    }
+                    size
                 }
             }
         };