Move index update from table logic to interpreter

minisql/src/interpreter.rs

@@ -120,7 +120,7 @@ impl State {
                 let column_position: ColumnPosition = table.schema.column_position_from_column_name(&column_name)?;
 
                 let mut index: ColumnIndex = ColumnIndex::new();
-                let _ = index.update_from_table(&table, column_position)?;
+                let _ = update_index_from_table(&mut index, &table, column_position)?;
 
                 table.attach_index(column_position, index); 
                 Ok(Response::IndexCreated)
@@ -129,6 +129,27 @@ impl State {
     }
 }
 
+// Should be used in the case when an indexed is created after the table has existed for a
+// while. In such a case you need to build the index from the already existing rows.
+fn update_index_from_table(column_index: &mut ColumnIndex, table: &Table, column_position: ColumnPosition) -> DbResult<()> {
+    for (id, row) in &table.rows {
+        let value = match row.get(column_position) {
+            Some(Value::Indexable(value)) => {
+                value.clone()
+            },
+            Some(_) => {
+                let column_name: ColumnName = table.schema.column_name_from_column_position(column_position)?;
+                return Err(Error::AttemptToIndexNonIndexableColumn(table.schema.table_name.to_string(), column_name))
+            },
+            None => {
+                return Err(Error::ColumnPositionDoesNotExist(table.schema.table_name.to_string(), column_position))
+            }
+        };
+        column_index.add(value, *id)
+    }
+    Ok(())
+}
+
 // TODO: Give a better name to something that you can respond to with rows
 trait SqlResponseConsumer {
     // TODO: