fix(migrate): verify write roundtrip before bailout

mempalace/migrate.py

@@ -22,6 +22,7 @@ import errno
 import os
 import shutil
 import sqlite3
+import uuid
 from collections import defaultdict
 from datetime import datetime
 
@@ -155,6 +156,55 @@ def confirm_destructive_action(
     return True
 
 
+def _result_ids(result) -> list:
+    """Return ids from either the backend typed result or raw Chroma dict."""
+
+    if isinstance(result, dict):
+        return list(result.get("ids") or [])
+
+    return list(getattr(result, "ids", []) or [])
+
+
+def collection_write_roundtrip_works(col) -> bool:
+    """Return True only if the collection can upsert, read, and delete.
+
+    Some ChromaDB 0.6.x -> 1.5.x migrated collections remain readable while
+    writes and deletes silently no-op. A plain ``count()`` probe misses that
+    failure mode, so migrate must verify an actual write round-trip before
+    deciding that no rebuild is needed.
+    """
+
+    probe_id = f"_mempalace_migrate_probe_{uuid.uuid4().hex}"
+    probe_doc = "mempalace migrate write round-trip probe"
+    probe_meta = {
+        "wing": "_mempalace_probe",
+        "room": "_mempalace_probe",
+        "source_file": "mempalace_migrate_probe",
+        "chunk_index": 0,
+    }
+
+    try:
+        col.upsert(
+            ids=[probe_id],
+            documents=[probe_doc],
+            metadatas=[probe_meta],
+        )
+
+        after_upsert = col.get(ids=[probe_id], include=[])
+        if probe_id not in _result_ids(after_upsert):
+            return False
+
+        col.delete(ids=[probe_id])
+
+        after_delete = col.get(ids=[probe_id], include=[])
+        if probe_id in _result_ids(after_delete):
+            return False
+
+        return True
+    except Exception:
+        return False
+
+
 def migrate(palace_path: str, dry_run: bool = False, confirm: bool = False):
     """Migrate a palace to the currently installed ChromaDB version."""
     from .backends.chroma import ChromaBackend
@@ -179,13 +229,24 @@ def migrate(palace_path: str, dry_run: bool = False, confirm: bool = False):
     print(f"  Source:    ChromaDB {source_version}")
     print(f"  Target:    ChromaDB {target_version}")
 
-    # Try reading with current chromadb first
+    # Try reading and writing with current chromadb first.
+    #
+    # A plain count() is not enough: some 0.6.x -> 1.5.x migrated collections
+    # are readable but silently drop upsert/delete operations. In that state,
+    # migrate must rebuild from SQLite instead of returning "No migration needed."
     try:
         col = ChromaBackend().get_collection(palace_path, "mempalace_drawers")
         count = col.count()
-        print(f"\n  Palace is already readable by chromadb {target_version}.")
+
+        if collection_write_roundtrip_works(col):
+            print(f"\n Palace is already readable and writable by chromadb {target_version}.")
             print(f" {count} drawers found. No migration needed.")
             return True
+
+        print(
+            f"\n Palace is readable by chromadb {target_version}, but write/delete verification failed."
+        )
+        print(" Rebuilding from SQLite to restore native write/delete behavior...")
     except Exception:
         print(f"\n Palace is NOT readable by chromadb {target_version}.")
         print(" Extracting from SQLite directly...")

tests/test_migrate.py

@@ -4,7 +4,7 @@ import os
 from types import SimpleNamespace
 from unittest.mock import MagicMock, patch
 
-from mempalace.migrate import _restore_stale_palace, migrate
+from mempalace.migrate import collection_write_roundtrip_works, _restore_stale_palace, migrate
 
 
 def test_migrate_requires_palace_database(tmp_path, capsys):
@@ -101,3 +101,102 @@ def test_restore_stale_palace_logs_and_swallows_on_failure(tmp_path, capsys):
     assert "CRITICAL" in out
     assert os.fspath(palace_path) in out
     assert os.fspath(stale_path) in out
+
+
+class _FakeGetResult:
+    def __init__(self, ids):
+        self.ids = ids
+
+
+class _WritableFakeCollection:
+    def __init__(self):
+        self.ids = set()
+        self.deleted = []
+
+    def upsert(self, *, ids, documents, metadatas):
+        self.ids.update(ids)
+
+    def get(self, *, ids, include=None):
+        return _FakeGetResult([drawer_id for drawer_id in ids if drawer_id in self.ids])
+
+    def delete(self, *, ids=None, where=None):
+        for drawer_id in ids or []:
+            self.ids.discard(drawer_id)
+            self.deleted.append(drawer_id)
+
+
+class _SilentWriteDropCollection(_WritableFakeCollection):
+    def upsert(self, *, ids, documents, metadatas):
+        return None
+
+
+class _SilentDeleteDropCollection(_WritableFakeCollection):
+    def delete(self, *, ids=None, where=None):
+        self.deleted.extend(ids or [])
+
+
+def test_collection_write_roundtrip_works_when_probe_persists_and_deletes():
+    col = _WritableFakeCollection()
+
+    assert collection_write_roundtrip_works(col) is True
+    assert col.ids == set()
+    assert len(col.deleted) == 1
+
+
+def test_collection_write_roundtrip_fails_when_upsert_silently_drops():
+    col = _SilentWriteDropCollection()
+
+    assert collection_write_roundtrip_works(col) is False
+    assert col.ids == set()
+
+
+def test_collection_write_roundtrip_fails_when_delete_silently_drops():
+    col = _SilentDeleteDropCollection()
+
+    assert collection_write_roundtrip_works(col) is False
+    assert len(col.ids) == 1
+
+
+def test_migrate_dry_run_rebuilds_when_collection_is_readable_but_not_writable(tmp_path, capsys):
+    palace_dir = tmp_path / "palace"
+    palace_dir.mkdir()
+    (palace_dir / "chroma.sqlite3").write_text("db")
+
+    fake_col = MagicMock()
+    fake_col.count.return_value = 102
+
+    drawers = [
+        {
+            "id": "id1",
+            "document": "hello",
+            "metadata": {"wing": "test-wing", "room": "general"},
+        }
+    ]
+
+    with (
+        patch("mempalace.migrate.detect_chromadb_version", return_value="1.x"),
+        patch("mempalace.backends.chroma.ChromaBackend") as mock_backend,
+        patch(
+            "mempalace.migrate.collection_write_roundtrip_works", return_value=False
+        ) as mock_probe,
+        patch(
+            "mempalace.migrate.extract_drawers_from_sqlite", return_value=drawers
+        ) as mock_extract,
+    ):
+        mock_backend.backend_version.return_value = "1.5.8"
+        mock_backend.return_value.get_collection.return_value = fake_col
+
+        result = migrate(str(palace_dir), dry_run=True)
+
+    out = capsys.readouterr().out
+
+    assert result is True
+    mock_probe.assert_called_once_with(fake_col)
+    mock_extract.assert_called_once_with(
+        os.path.join(os.path.abspath(os.fspath(palace_dir)), "chroma.sqlite3")
+    )
+
+    assert "readable by chromadb 1.5.8, but write/delete verification failed" in out
+    assert "Rebuilding from SQLite" in out
+    assert "Extracted 1 drawers from SQLite" in out
+    assert "DRY RUN" in out