> ## Documentation Index
> Fetch the complete documentation index at: https://docs.turingdb.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Time Travel

> You can time travel in you graph databases and see the commit history

<Tabs>
  <Tab title="Cypher">
    ```jsx theme={null}
    // Show commit history
    CALL db.history()

    // Read a previous commit
    checkout c0a6ce3c0315be7a

    // Query graph at specific commit
    MATCH (n:Person)-[e:KNOWS]->(m:Person)
    WHERE n.name = 'Jane'
    AND n.name = 'John'
    RETURN n, e, m
    ```
  </Tab>

  <Tab title="Python SDK">
    ```python theme={null}
    # Show commit history
    client.query("CALL db.history()")

    # Read a previous commit
    client.checkout(change="main", commit="c0a6ce3c0315be7a")

    # Query graph at specific commit
    client.query("""
    MATCH (n:Person)-[e:KNOWS]->(m:Person)
    WHERE n.name = 'Jane'
    AND n.name = 'John'
    RETURN n, e, m
    """)
    ```
  </Tab>
</Tabs>

## Lazy Commit Loading

TuringDB lazily loads commits from disk. When a graph is loaded, only the **HEAD commit** (the latest commit on the current branch) is fully loaded into memory. All other commits are registered but their data remains on disk until explicitly requested.

This means that to query a past commit, its data must first be loaded into memory using the `LOAD COMMIT` command:

```jsx theme={null}
LOAD COMMIT 'c0a6ce3c0315be7a'
```

<Check>
  **When do I need `LOAD COMMIT`?**

  * **TuringDB CLI**: The `checkout` command automatically loads the commit for you — no need to call `LOAD COMMIT` manually.
  * **Python SDK**: `client.checkout()` automatically loads the commit for you — no need to call `LOAD COMMIT` manually.
  * **REST API (`/query` endpoint)**: If you send Cypher queries directly to the `/query` endpoint, you **must** call `LOAD COMMIT '<hash>'` explicitly before querying any commit that is not the HEAD commit at startup time.
</Check>

### Example: Querying a Past Commit via the REST API

```jsx theme={null}
// Step 1: Load the commit into memory
LOAD COMMIT 'be9643a1c03f8e2b'

// Step 2: Now you can query at that commit
MATCH (n:Person)-[e:KNOWS]->(m:Person)
RETURN n.name, m.name
```

<Warning>
  If you try to query a commit that has not been loaded, TuringDB will return an error:
  `Commit not loaded to memory - use LOAD COMMIT '<hash>' to load a commit`
</Warning>

`LOAD COMMIT` is **idempotent** — calling it on an already-loaded commit is a no-op and returns immediately.