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

databend_sqlalchemy/dml.py

@@ -277,6 +277,7 @@ def __repr__(self):
 
 class CSVFormat(CopyFormat):
     format_type = "CSV"
+    inherit_cache = False
 
     def __init__(
         self,
@@ -340,12 +341,13 @@ def __init__(
             if binary_format not in ["HEX", "BASE64"]:
                 raise TypeError('Binary Format should be "HEX" or "BASE64".')
             self.options["BINARY_FORMAT"] = binary_format
-        if compression:
+        if compression and compression is not Compression.NONE:
             self.options["COMPRESSION"] = compression.value
 
 
 class TSVFormat(CopyFormat):
     format_type = "TSV"
+    inherit_cache = False
 
     def __init__(
         self,
@@ -366,12 +368,13 @@ def __init__(
             if len(str(field_delimiter).encode().decode("unicode_escape")) != 1:
                 raise TypeError("Field Delimiter should be a single character")
             self.options["FIELD_DELIMITER"] = f"{repr(field_delimiter)}"
-        if compression:
+        if compression and compression is not Compression.NONE:
             self.options["COMPRESSION"] = compression.value
 
 
 class NDJSONFormat(CopyFormat):
     format_type = "NDJSON"
+    inherit_cache = False
 
     def __init__(
         self,
@@ -396,12 +399,13 @@ def __init__(
                     'Missing Field As should be "ERROR", "NULL", "FIELD_DEFAULT" or "TYPE_DEFAULT".'
                 )
             self.options["MISSING_FIELD_AS"] = f"{missing_field_as}"
-        if compression:
+        if compression and compression is not Compression.NONE:
             self.options["COMPRESSION"] = compression.value
 
 
 class ParquetFormat(CopyFormat):
     format_type = "PARQUET"
+    inherit_cache = False
 
     def __init__(
         self,
@@ -416,7 +420,7 @@ def __init__(
                     'Missing Field As should be "ERROR" or "FIELD_DEFAULT".'
                 )
             self.options["MISSING_FIELD_AS"] = f"{missing_field_as}"
-        if compression:
+        if compression and compression is not Compression.NONE:
             if compression not in [Compression.ZSTD, Compression.SNAPPY]:
                 raise TypeError(
                     'Compression should be None, ZStd, or Snappy.'

tests/test_copy_format.py

@@ -0,0 +1,57 @@
+#!/usr/bin/env python
+
+from sqlalchemy.testing import fixtures, assert_raises_message
+from sqlalchemy.testing.assertions import AssertsCompiledSQL
+
+from databend_sqlalchemy import (
+    CSVFormat,
+    TSVFormat,
+    NDJSONFormat,
+    ParquetFormat,
+    Compression,
+)
+
+
+class CompileCopyFormatCompressionTest(fixtures.TestBase, AssertsCompiledSQL):
+
+    __only_on__ = "databend"
+
+    _FORMATS = [
+        (CSVFormat, "CSV"),
+        (TSVFormat, "TSV"),
+        (NDJSONFormat, "NDJSON"),
+        (ParquetFormat, "PARQUET"),
+    ]
+
+    def test_no_compression_emits_no_option(self):
+        # ``None`` and the ``Compression.NONE`` sentinel both mean uncompressed.
+        # Regression: ``Compression.NONE`` is a truthy Enum member, so the old
+        # ``if compression:`` guard treated it as "a codec was set" — emitting a
+        # spurious ``COMPRESSION = NONE`` option and, for ParquetFormat, raising.
+        for fmt_cls, type_ in self._FORMATS:
+            expected = f"FILE_FORMAT = (TYPE = {type_})"
+            self.assert_compile(fmt_cls(), expected)
+            self.assert_compile(fmt_cls(compression=Compression.NONE), expected)
+
+    def test_explicit_codec_is_emitted(self):
+        for fmt_cls, type_, codec in [
+            (CSVFormat, "CSV", Compression.GZIP),
+            (TSVFormat, "TSV", Compression.GZIP),
+            (NDJSONFormat, "NDJSON", Compression.GZIP),
+            (ParquetFormat, "PARQUET", Compression.ZSTD),
+            (ParquetFormat, "PARQUET", Compression.SNAPPY),
+        ]:
+            self.assert_compile(
+                fmt_cls(compression=codec),
+                f"FILE_FORMAT = (TYPE = {type_}, COMPRESSION = {codec.value})",
+            )
+
+    def test_parquet_rejects_unsupported_codec(self):
+        # ParquetFormat still rejects codecs its writer can't use.
+        for codec in [Compression.GZIP, Compression.BZ2, Compression.ZIP]:
+            assert_raises_message(
+                TypeError,
+                "Compression should be None, ZStd, or Snappy.",
+                ParquetFormat,
+                compression=codec,
+            )