Emit LIMIT -1 when offset is used without limit (#821)

* Emit LIMIT -1 when offset is used without limit, closes #816

SQLite requires a LIMIT clause to appear before OFFSET, so passing offset
without limit generated invalid SQL such as:

    select * from "t" offset 2

which raised OperationalError: near "2": syntax error.

A negative limit means "no upper bound" in SQLite, so "limit -1 offset N"
returns all rows from position N onwards.

Fixed in three places that build LIMIT/OFFSET SQL:

- Queryable.rows_where() - also covers pks_and_rows_where()
- Table.search_sql() - also covers search()
- the "sqlite-utils rows" CLI command

* Remove duplicate comments

---------

Co-authored-by: ethanhawkes-gif <259455325+ethanhawkes-gif@users.noreply.github.com>

sqlite_utils/cli.py

@@ -2478,6 +2478,8 @@ def rows(
     if limit:
         sql += f" limit {limit}"
     if offset:
+        if not limit:
+            sql += " limit -1"
         sql += f" offset {offset}"
     ctx.invoke(
         query,

sqlite_utils/db.py

@@ -2064,6 +2064,10 @@ class Queryable:
         if limit is not None:
             sql += f" limit {limit}"
         if offset is not None:
+            # SQLite requires a limit clause before offset - a negative limit
+            # means "no upper bound", so offset works without an explicit limit
+            if limit is None:
+                sql += " limit -1"
             sql += f" offset {offset}"
         cursor = self.db.execute(sql, where_args or [])
         columns = dedupe_keys(c[0] for c in cursor.description)
@@ -3732,6 +3736,8 @@ class Table(Queryable):
         if limit is not None:
             limit_offset += f" limit {limit}"
         if offset is not None:
+            if limit is None:
+                limit_offset += " limit -1"
             limit_offset += f" offset {offset}"
         return sql.format(
             dbtable=quote_identifier(self.name),

tests/test_cli.py

@@ -1183,6 +1183,11 @@ def test_query_memory_does_not_create_file(tmpdir):
             ["-c", "name", "--limit", "1", "--offset", "1"],
             '[{"name": "Pancakes"}]',
         ),
+        # --offset without --limit
+        (
+            ["-c", "name", "--offset", "1"],
+            '[{"name": "Pancakes"}]',
+        ),
         # --where
         (
             ["-c", "name", "--where", "id = 1"],

tests/test_fts.py

@@ -112,6 +112,17 @@ def test_search_limit_offset(fresh_db):
     )
 
 
+def test_search_offset_without_limit(fresh_db):
+    table = fresh_db["t"]
+    table.insert_all(search_records)
+    table.enable_fts(["text", "country"], fts_version="FTS4")
+    assert [row["rowid"] for row in table.search("are", order_by="rowid")] == [1, 2]
+    assert [
+        row["rowid"] for row in table.search("are", offset=1, order_by="rowid")
+    ] == [2]
+    assert table.search_sql(offset=1).strip().endswith("limit -1 offset 1")
+
+
 @pytest.mark.parametrize("fts_version", ("FTS4", "FTS5"))
 def test_search_where(fresh_db, fts_version):
     table = fresh_db["t"]

tests/test_rows.py

@@ -59,6 +59,9 @@ def test_rows_where_order_by(where, order_by, expected_ids, fresh_db):
         (None, 3, [1, 2, 3]),
         (0, 3, [1, 2, 3]),
         (3, 3, [4, 5, 6]),
+        # offset without limit should return every remaining row
+        (97, None, [98, 99, 100]),
+        (0, None, list(range(1, 101))),
     ],
 )
 def test_rows_where_offset_limit(fresh_db, offset, limit, expected):
@@ -70,6 +73,12 @@ def test_rows_where_offset_limit(fresh_db, offset, limit, expected):
     ]
 
 
+def test_pks_and_rows_where_offset_without_limit(fresh_db):
+    table = fresh_db["rows"]
+    table.insert_all([{"id": id} for id in range(1, 6)], pk="id")
+    assert [pk for pk, _ in table.pks_and_rows_where(offset=3, order_by="id")] == [4, 5]
+
+
 def test_pks_and_rows_where_rowid(fresh_db):
     table = fresh_db["rowid_table"]
     table.insert_all({"number": i + 10} for i in range(3))