[coverage] Conformance findings: STATEMENT-022

从转发到 backend.cancel_command(active_command_id) 的 cancel() 路径开始，然后检查 tests/ 下 coverage PR diff 中失败的测试 test_simultaneous_statement_cancellation。完成的标准是并发取消能够在不抛出异常的情况下完成，并且针对该 statement 恰好发出一个 CancelOperation RPC。

Summary

Surfaced by the multi-language coverage fan-out while conformance-testing these SPEC-IDs against databricks/databricks-sql-python. Each finding is committed as an expected-failure (xfail) test in the coverage PR — the test asserts the CORRECT (post-fix) behavior and stays red until THIS driver (databricks/databricks-sql-python) is fixed, then flips green as a tripwire.

Findings

• STATEMENT-022 [thrift]: Thrift: Cursor.cancel() does not deduplicate concurrent cancels on the same statement — 3 threads emit 3 CancelOperation RPCs where the spec requires exactly 1, because cancel() forwards straight to backend.cancel_command(active_command_id) with no in-flight-cancel guard
  • failing test: test_simultaneous_statement_cancellation (see the coverage PR diff under tests/)

Reproduce & Expected

STATEMENT-022 — Validates driver handles multiple threads calling CancelOperation on same statement without deadlock or crash.

Reproduce:

SELECT a.*, b.* FROM main.tpcds_sf1_delta.catalog_returns a CROSS JOIN range(1, 10000) b ORDER BY a.cr_order_number, b.id

Expected (per the shared spec):

• completes without an exception
• [thrift] exactly 1 CancelOperation call(s)
• [sea] between 1 and 3 CancelStatement call(s)

Context

• The behavior was first fixed in a DIFFERENT driver — reference PR: https://github.com/adbc-drivers/databricks/pull/614 — which seeded the shared language-neutral spec. This issue tracks the same conformance gap in databricks/databricks-sql-python; the reference PR is for cross-referencing the intended behavior, NOT a change to this repo.
• Coverage PR carrying the reproducing xfail test(s): https://github.com/databricks/databricks-driver-test/pull/1069