feat: support delete-where

btree.h

@@ -431,21 +431,26 @@ cursor_t *leaf_node_find(table_t *table, uint32_t page_num, uint32_t key)
  * it still occupy disk space.
  *
  * 4) If the `num_cells` of leaf node is ZERO, then just return and delete nothing.
+ * The returned value denote whether if we deleted a cell from B+Tree.
  **/
-void leaf_node_fake_delete(cursor_t *cursor, uint32_t key_to_delete)
+bool leaf_node_fake_delete(cursor_t *cursor, uint32_t key_to_delete)
 {
     uint32_t cell_num = cursor->cell_num;
     void *node = get_page(cursor->table->pager, cursor->page_num);
 
     uint32_t num_cells = *leaf_node_num_cells(node);
 
+    if (num_cells == 0)
+        return false;
+
     assert(cell_num < num_cells && *leaf_node_key(node, cell_num) == key_to_delete);
 
     for (uint32_t i = cell_num; i + 1 < num_cells; i++)
     {
         memcpy(leaf_node_cell(node, i), leaf_node_cell(node, i + 1), LEAF_NODE_CELL_SIZE);
     }
     *leaf_node_num_cells(node) = num_cells - 1;
+    return true;
 }
 
 /**

cursor.h

@@ -9,10 +9,17 @@ cursor_t *table_start(table_t *table)
     cursor_t *cursor = table_find(table, 0);
     void *node = get_page(cursor->table->pager, cursor->page_num);
     uint32_t num_cells = *leaf_node_num_cells(node);
-    cursor->end_of_table = (num_cells == 0);
+    cursor->end_of_table = (num_cells == 0 && *leaf_node_next_leaf(node) == 0);
     return cursor;
 }
 
+/* Whether if the node(page) that the cursor points to is empty. */
+bool cursor_empty(cursor_t *cursor)
+{
+    void *page = get_page(cursor->table->pager, cursor->page_num);
+    return *leaf_node_num_cells(page) == 0;
+}
+
 // get row address of the argument cursor
 void *cursor_value(cursor_t *cursor)
 {

sql-statement/statement.h

@@ -19,11 +19,11 @@ typedef enum
 
 typedef struct
 {
-    statement_type_t type;   /* SELECT, UPDATE, DELETE, etc. */
-    row_t row_value;         /* The row value of INSERT SQL  */
-    const char *table_name;  /* table name                   */
-    schema_node_t *schemas;  /* SELECT column items list     */
-    condition_t *conditions; /* WHERE conditions             */
+    statement_type_t type;   // SELECT, UPDATE, DELETE, etc.
+    row_t row_value;         // The row value of INSERT SQL
+    const char *table_name;  // table name
+    schema_node_t *schemas;  // SELECT/UPDATE column items list
+    condition_t *conditions; // WHERE conditions
 } statement_t;
 
 static inline void statement_set(

sql-vm/vm.h

@@ -57,9 +57,12 @@ execute_result_t execute_select(statement_t *statement, table_t *table)
     uint32_t i = 0;
     while (!(cursor->end_of_table))
     {
-        deserialize_row(cursor_value(cursor), &row);
-        i++;
-        print_row(&row);
+        if (!cursor_empty(cursor))
+        {
+            deserialize_row(cursor_value(cursor), &row);
+            i++;
+            print_row(&row);
+        }
         cursor_advance(cursor);
     }
     printf("total %u rows\n", i);
@@ -76,8 +79,7 @@ execute_result_t execute_select_where(statement_t *statement, table_t *table)
     while (!(cursor->end_of_table))
     {
         deserialize_row(cursor_value(cursor), &row);
-
-        if (test_condition(statement->conditions, &row))
+        if (!cursor_empty(cursor) && test_condition(statement->conditions, &row))
         {
             cnt++;
             print_fields(&row, flags);
@@ -161,8 +163,24 @@ execute_result_t execute_delete(statement_t *statement, table_t *table)
 execute_result_t execute_delete_where(statement_t *statement, table_t *table)
 {
     /* There is bugs while scanning B+Tree and deleting at the same time. */
-    TODO(__FILE__, __LINE__);
-    return EXECUTE_UNKNOWN_STATEMENT;
+    // TODO(__FILE__, __LINE__);
+    cursor_t *cursor = table_start(table);
+    row_t row;
+    uint32_t cnt = 0;
+    while (!(cursor->end_of_table))
+    {
+        deserialize_row(cursor_value(cursor), &row);
+        if (test_condition(statement->conditions, &row) &&
+            leaf_node_fake_delete(cursor, row.id))
+        {
+            cnt += 1;
+            cursor->cell_num -= 1;
+        }
+        cursor_advance(cursor);
+    }
+    free(cursor);
+    printf("total %u rows were deleted. \n", cnt);
+    return EXECUTE_SUCCESS;
 }
 
 execute_result_t execute_commit(statement_t *statement, table_t *table)