fix: treat Compression.NONE sentinel as uncompressed in COPY INTO formats

[simozzy]

Problem

Compression.NONE is a truthy Enum member, so the if compression: guard in CSVFormat, TSVFormat, NDJSONFormat, and ParquetFormat treats the no-compression sentinel as "a codec was specified":

if compression:                                   # Compression.NONE is truthy!
    if compression not in [Compression.ZSTD, Compression.SNAPPY]:
        raise TypeError('Compression should be None, ZStd, or Snappy.')
    self.options["COMPRESSION"] = compression.value

• ParquetFormat(compression=Compression.NONE) raises TypeError: Compression should be None, ZStd, or Snappy. — even though NONE is the "no compression" case.
• The CSV/TSV/NDJSON classes don't raise, but emit a spurious COMPRESSION = NONE option for the sentinel.

Fix

Skip the block for both None and the Compression.NONE sentinel, so the uncompressed case renders no COMPRESSION option:

if compression and compression is not Compression.NONE:
    ...

Applied to all four format classes. Explicit codecs are unchanged, and ParquetFormat still rejects codecs its writer can't use (gzip/bz2/zip).

The four format classes also now set inherit_cache = False (matching CopyIntoTable/CopyIntoLocation), which silences SQLAlchemy's "will not make use of SQL compilation caching" warning when a format is compiled — needed for the new compile tests to pass under the suite's warning-as-error config.

Tests

tests/test_copy_format.py — a fixtures.TestBase + AssertsCompiledSQL class mirroring tests/test_copy_into.py, asserting the rendered FILE_FORMAT = (...) via assert_compile:

• None and Compression.NONE emit no COMPRESSION option, across all four classes.
• Explicit codecs are still emitted where valid.
• ParquetFormat still raises TypeError for unsupported codecs.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: e9239985e4

ℹ️ About Codex in GitHub

Codex has been enabled to automatically review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

When you sign up for Codex through ChatGPT, Codex can also answer questions or update the PR, like "@codex address that feedback".

[chatgpt-codex-connector]

Reject NONE for Parquet instead of using defaults

When callers pass ParquetFormat(compression=Compression.NONE), this condition now skips validation and emits no COMPRESSION option. For Parquet, Databend only supports ZSTD/SNAPPY for this option and the omitted-option default is ZSTD, so a user asking for no compression silently gets ZSTD-compressed output instead of the previous clear rejection. Keep Compression.NONE rejected for Parquet rather than treating it like None.

Useful? React with 👍 / 👎.