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fix(trino): coerce LIMIT before SQL interpolation #2626

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fix(trino): coerce LIMIT before SQL interpolation #2626

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15 changes: 15 additions & 0 deletions core/wren/src/wren/connector/trino.py
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Original file line number Diff line number Diff line change
Expand Up @@ -456,6 +456,20 @@ def _import_trino():
) from e


def _coerce_limit(limit: int | None) -> int | None:
"""Validate and coerce a user-supplied ``limit`` to a non-negative ``int``.

``int(limit)`` rejects strings like ``"5 OR 1=1"`` so the value can be
safely interpolated into SQL. Negative limits are also rejected.
"""
if limit is None:
return None
coerced = int(limit)
if coerced < 0:
raise ValueError(f"limit must be non-negative, got {coerced}")
return coerced
Comment on lines +459 to +470

@coderabbitai coderabbitai Bot Jul 30, 2026

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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Reject fractional negative limits before coercion.

int(-0.5) becomes 0, so the check at Line 468 accepts an originally negative limit and executes LIMIT 0. Validate the original numeric value before truncation, or reject non-integral numeric inputs; add a regression test for limit=-0.5.

🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@core/wren/src/wren/connector/trino.py` around lines 459 - 470, Update
_coerce_limit to reject negative fractional numeric inputs before int coercion,
while preserving acceptance of valid non-negative integral limits and existing
rejection of negative integers. Add a regression test confirming limit=-0.5
raises ValueError rather than becoming LIMIT 0.



class TrinoConnector(ConnectorABC):
"""Native trino DB-API connector that bypasses ibis-project."""

Expand All @@ -482,6 +496,7 @@ def __init__(self, connection_info):
self._closed = False

def query(self, sql: str, limit: int | None = None) -> pa.Table:
limit = _coerce_limit(limit)
trino = _import_trino()

if limit is not None:
Expand Down
45 changes: 45 additions & 0 deletions core/wren/tests/unit/test_trino_coerce_limit.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,45 @@
"""Trino query must coerce LIMIT before SQL interpolation."""

from __future__ import annotations

from unittest.mock import MagicMock, patch

import pytest

from wren.connector import trino as trino_mod


def _connector():
c = object.__new__(trino_mod.TrinoConnector)
c.connection = MagicMock()
c._closed = False
return c


def test_reject_negative_limit():
c = _connector()
with pytest.raises(ValueError, match="non-negative"):
c.query("SELECT 1", limit=-1)


def test_reject_injection_string():
c = _connector()
with pytest.raises(ValueError):
c.query("SELECT 1", limit="1; DROP TABLE t")


def test_numeric_string_limit_interpolated():
c = _connector()
cursor = MagicMock()
c.connection.cursor.return_value = cursor
with patch.object(trino_mod, "_import_trino") as imp, patch.object(
trino_mod, "_build_trino_arrow_table", return_value="tbl"
):
trino_pkg = MagicMock()
trino_pkg.exceptions.TrinoQueryError = type("TrinoQueryError", (Exception,), {})
imp.return_value = trino_pkg
out = c.query("SELECT 1", limit="4")
assert out == "tbl"
executed = cursor.execute.call_args[0][0]
assert "LIMIT 4" in executed
assert "DROP" not in executed
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