[coverage] Conformance findings: PARAMQUERY-022,PARAMQUERY-023

Bắt đầu với diff của tests/ trong PR về coverage và tái hiện SELECT ? AS v cho PARAMQUERY-022 và PARAMQUERY-023. Truy vết đường dẫn parameter-binding của Thrift DECIMAL trong connector Node.js, chỉ sử dụng PR ODBC tham chiếu để hiểu hành vi dự kiến. Được xem là hoàn tất khi các trường hợp xfail pass: precision và scale được khai báo được giữ nguyên, và 123.45 không bao giờ bị cắt ngầm.

Summary

Surfaced by the multi-language coverage fan-out while conformance-testing these SPEC-IDs against databricks/databricks-sql-nodejs. 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-nodejs) is fixed, then flips green as a tripwire.

Findings

• PARAMQUERY-022 [thrift]: Thrift DECIMAL parameter binding emits DECIMAL(precision,0) — scale hard-coded to 0 — so "123.45" declares decimal(3,0) instead of a scale-carrying decimal; SEA correctly emits decimal(5,2)
  • failing test: decimal target — "123.45" bound as DECIMAL comes back a decimal carrying scale, digits intact (see the coverage PR diff under tests/)
• PARAMQUERY-023 [thrift]: Thrift DECIMAL parameter binding silently TRUNCATES fractional digits: "123.45" round-trips as 123 (data corruption) via a scale-0 wire type; it neither preserves the value nor raises numeric-out-of-range, while the SEA path is lossless
  • failing test: scale-less decimal target — "123.45" is never silently truncated to 123 (see the coverage PR diff under tests/)

Reproduce & Expected

PARAMQUERY-022 — Verify a DECIMAL/NUMERIC target with a declared precision and scale sends the parameter as a DECIMAL carrying THAT precision/scale, so the bare-marker result column is a decimal of the declared shape and the fractional digits survive.

Reproduce:

SELECT ? AS v

Expected (per the shared spec):

• result has exactly 1 row(s)
• col 0, row 0 == '123.45' (type Decimal128)
• full assertion contract:

result:
- row_count: 1
- column:
    index: 0
    row: 0
    type: Decimal128
    equals: '123.45'
- result_column_type_matches_target: true

PARAMQUERY-023 — Verify a DECIMAL/NUMERIC target with NO declared scale does not silently truncate fractional digits. An under-specified decimal target must not be forced to scale 0 — the value is preserved losslessly (the reference driver keeps the lossless value-derived type and lets the server infer the decimal).

Reproduce:

SELECT ? AS v

Expected (per the shared spec):

• result has exactly 1 row(s)
• full assertion contract:

result:
- row_count: 1
- value_preserved_losslessly: '123.45'

Context

• The behavior was first fixed in a DIFFERENT driver — reference PR: https://github.com/databricks/databricks-odbc/pull/167 — which seeded the shared language-neutral spec. This issue tracks the same conformance gap in databricks/databricks-sql-nodejs; 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/1061