llm logs backup command, closes #879

docs/help.md

@@ -250,6 +250,7 @@ Options:
 
 Commands:
   list*   Show logged prompts and their responses
+  backup  Backup your logs database to this file
   off     Turn off logging for all prompts
   on      Turn on logging for all prompts
   path    Output the path to the logs.db file
@@ -278,6 +279,17 @@ Options:
   --help  Show this message and exit.
 ```
 
+(help-logs-backup)=
+#### llm logs backup --help
+```
+Usage: llm logs backup [OPTIONS] PATH
+
+  Backup your logs database to this file
+
+Options:
+  --help  Show this message and exit.
+```
+
 (help-logs-on)=
 #### llm logs on --help
 ```

docs/logging.md

@@ -234,6 +234,17 @@ You can also use [Datasette](https://datasette.io/) to browse your logs like thi
 datasette "$(llm logs path)"
 ```
 
+(logging-backup)=
+
+### Backing up your database
+
+You can backup your logs to another file using the `llm logs backup` command:
+
+```bash
+llm logs backup /tmp/backup.db
+```
+This uses SQLite [VACCUM INTO](https://sqlite.org/lang_vacuum.html#vacuum_with_an_into_clause) under the hood.
+
 (logging-sql-schema)=
 
 ## SQL schema

llm/cli.py

@@ -1085,6 +1085,22 @@ def logs_status():
     )
 
 
+@logs.command(name="backup")
+@click.argument("path", type=click.Path(dir_okay=True, writable=True))
+def backup(path):
+    "Backup your logs database to this file"
+    logs_path = logs_db_path()
+    path = pathlib.Path(path)
+    db = sqlite_utils.Database(logs_path)
+    try:
+        db.execute("vacuum into ?", [str(path)])
+    except Exception as ex:
+        raise click.ClickException(str(ex))
+    click.echo(
+        "Backed up {} to {}".format(_human_readable_size(path.stat().st_size), path)
+    )
+
+
 @logs.command(name="on")
 def logs_turn_on():
     "Turn on logging for all prompts"

tests/test_llm_logs.py

@@ -5,6 +5,7 @@ from llm import Fragment
 from ulid import ULID
 import datetime
 import json
+import pathlib
 import pytest
 import re
 import sqlite_utils
@@ -842,3 +843,19 @@ def test_expand_fragment_markdown(fragments_fixture):
     expected_prefix = f"### Prompt fragments\n\n<details><summary>{hash}</summary>\nThis is fragment 5"
     assert interesting_bit.startswith(expected_prefix)
     assert interesting_bit.endswith("</details>")
+
+
+def test_logs_backup(logs_db):
+    assert not logs_db.tables
+    runner = CliRunner()
+    with runner.isolated_filesystem():
+        runner.invoke(cli, ["-m", "echo", "simple prompt"])
+        assert logs_db.tables
+        expected_path = pathlib.Path("backup.db")
+        assert not expected_path.exists()
+        # Now back it up
+        result = runner.invoke(cli, ["logs", "backup", "backup.db"])
+        assert result.exit_code == 0
+        assert result.output.startswith("Backed up ")
+        assert result.output.endswith("to backup.db\n")
+        assert expected_path.exists()