Handle db.table(table_name).insert({}), closes #759

sqlite_utils/db.py

@@ -3179,6 +3179,20 @@ class Table(Queryable):
         return a list of ``(sql, parameters)`` 2-tuples which, when executed in
         order, perform the desired INSERT / UPSERT / REPLACE operation.
         """
+        # Dict-mode insert({}) has no explicit columns; SQLite spells that as
+        # DEFAULT VALUES. List mode with no columns is a different input shape.
+        if not list_mode and not all_columns:
+            or_clause = ""
+            if replace:
+                or_clause = " OR REPLACE"
+            elif ignore:
+                or_clause = " OR IGNORE"
+            sql = (
+                f"INSERT{or_clause} INTO {quote_identifier(self.name)} "
+                "DEFAULT VALUES"
+            )
+            return [(sql, []) for _ in chunk]
+
         if hash_id_columns and hash_id is None:
             hash_id = "id"
 
@@ -3603,7 +3617,11 @@ class Table(Queryable):
         assert (
             num_columns <= SQLITE_MAX_VARS
         ), "Rows can have a maximum of {} columns".format(SQLITE_MAX_VARS)
-        batch_size = max(1, min(batch_size, SQLITE_MAX_VARS // num_columns))
+        batch_size = (
+            1
+            if num_columns == 0
+            else max(1, min(batch_size, SQLITE_MAX_VARS // num_columns))
+        )
         self.last_rowid = None
         self.last_pk = None
         if truncate and self.exists():

tests/test_default_value.py

@@ -31,3 +31,24 @@ def test_quote_default_value(fresh_db, column_def, initial_value, expected_value
     assert expected_value == fresh_db.quote_default_value(
         fresh_db["foo"].columns[0].default_value
     )
+
+
+def test_insert_empty_record_uses_default_values(fresh_db):
+    fresh_db.execute("""
+        CREATE TABLE has_defaults (
+            id INTEGER PRIMARY KEY,
+            name TEXT,
+            timestamp TEXT DEFAULT CURRENT_TIMESTAMP,
+            is_active INTEGER NOT NULL DEFAULT 1
+        )
+        """)
+
+    table = fresh_db["has_defaults"]
+    table.insert({})
+
+    rows = list(table.rows)
+    assert len(rows) == 1
+    assert rows[0]["id"] == 1
+    assert rows[0]["name"] is None
+    assert rows[0]["timestamp"] is not None
+    assert rows[0]["is_active"] == 1