fix: virtual edges crash on every real Postgres source (dict_row)

kgrdbms/virtual.py

@@ -183,12 +183,15 @@ def _connect(dsn: str):
     if dsn.startswith(("postgresql://", "postgres://")):
         try:
             import psycopg  # type: ignore
+            from psycopg.rows import dict_row  # type: ignore
         except ModuleNotFoundError as e:  # pragma: no cover - env dependent
             raise RuntimeError(
                 "virtual edge needs the postgres driver: pip install "
                 "'knowledge-graph-rdbms[postgres]'"
             ) from e
-        return psycopg.connect(dsn), "%s"
+        # dict_row so fetchall() yields mappings — resolve() does dict(row) on
+        # each, which would fail on psycopg's default tuple rows.
+        return psycopg.connect(dsn, row_factory=dict_row), "%s"
     path = dsn
     for prefix in ("sqlite:///", "sqlite://"):
         if path.startswith(prefix):

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "knowledge-graph-rdbms"
-version = "0.1.6"
+version = "0.1.7"
 description = "A label property graph on an RDBMS (SQLite): nodes, typed edges, an append-only event log, and an optional MCP server."
 readme = "README.md"
 requires-python = ">=3.10"

tests/test_virtual.py

@@ -5,6 +5,7 @@
 synthesizes edges from it on traversal without ever copying rows in.
 """
 
+import os
 import sqlite3
 
 import pytest
@@ -122,3 +123,37 @@ def test_binding_roundtrips_and_unregisters(tmp_path):
     assert virtual.unregister(g, "CO_HELD_WITH") is True
     assert virtual.list_bindings(g) == []
     g.close()
+
+
+# Live-Postgres regression: resolve() does dict(row) on every result, so the
+# postgres path MUST use a dict row factory — with psycopg's default tuple rows
+# dict(row) raises. This is the bug that shipped in 0.1.6 (the sqlite stand-in
+# tests above never exercised the postgres branch). Gated: set KG_TEST_PG_DSN
+# (a throwaway database) to run it.
+_PG_DSN = os.environ.get("KG_TEST_PG_DSN")
+
+
+@pytest.mark.skipif(not _PG_DSN, reason="set KG_TEST_PG_DSN to run the live-postgres virtual-edge test")
+def test_virtual_resolves_against_postgres(tmp_path):
+    psycopg = pytest.importorskip("psycopg")
+    table = "kg_ve_regression"
+    with psycopg.connect(_PG_DSN, autocommit=True) as c:
+        c.execute(f"DROP TABLE IF EXISTS {table}")
+        c.execute(f"CREATE TABLE {table} (a text, b text, shared int)")
+        c.cursor().executemany(
+            f"INSERT INTO {table} VALUES (%s,%s,%s)", [("NVDA", "AMD", 12), ("NVDA", "TSM", 9)]
+        )
+    try:
+        g = Graph(path=tmp_path / "kg.db")
+        virtual.register(g, VirtualEdge(
+            edge_type="CO_HELD_WITH", source="id_slug",
+            query=f"SELECT b AS to_id, shared FROM {table} WHERE a = %s",
+            dsn=_PG_DSN, target_id_template="company:{value}", prop_cols=["shared"],
+        ))
+        out = virtual.augment(g, "company:NVDA", "out", None)
+        assert sorted((e.to_node, e.properties["shared"]) for _d, e, _f in out) \
+            == [("company:AMD", 12), ("company:TSM", 9)]
+        g.close()
+    finally:
+        with psycopg.connect(_PG_DSN, autocommit=True) as c:
+            c.execute(f"DROP TABLE IF EXISTS {table}")