---
title: "History and trash"
description: "The History keeps every row change in Records with undo, and the trash keeps deleted tables and columns for 30 days."
---

## History [#history]

Every row that `records_change` adds, changes or deletes in Records goes into the History as one entry, with the person, the agent, the table, the change and the values before and after. `history_list` shows three lists, newest first: the changes (`entries`), the actions (`actions`: each `records_change` call, each undo and each move to the trash) and the trash items (`trash`).

## Undo [#undo]

`history_undo` reverses row changes, and only row changes:

- With `entry`, it reverses one row change.
- With `action`, it reverses every row change one `records_change` call made, newest first. A call that changed no rows, such as `CREATE TABLE` or `ALTER TABLE`, has nothing to reverse and is refused with `42704`.
- The table needs a primary key: undo finds the row by it. On a table without one, undo is refused with `55000`. It is also refused with `55000` when the change altered the value of a `GENERATED ALWAYS AS IDENTITY` column; a `GENERATED BY DEFAULT AS IDENTITY` column does not block undo.
- When a newer change touched the same row, the undo is refused with `40001`; undo the newer ones first. Undoing again what was already undone answers `already_undone`.

Changes to a table's structure, such as creating a table or adding a column, cannot be undone. A table or column deleted with the functions below comes back through the trash, not through undo.

## Trash [#trash]

Records refuses `DROP TABLE` and `DROP COLUMN`. To delete a table, use `SELECT siglata.drop_table('table')`; to delete a column, `SELECT siglata.drop_column('table', 'column')`. The table or column goes to the trash and shows up in `history_list` with `kind: "trash"`.

`history_undo` with `trash` brings the item back. Bringing back an item that already came back answers `already_restored`. The trash keeps each item for 30 days; after that, Siglata deletes it for good.