SNOW-2248950: converter.py: parameter binding for decimal.Decimal produces incorrect SQL

[tboddyspargo]

Python version

3.11.6

Operating system and processor architecture

macOS-15.5-arm64-arm-64bit

Installed packages

snowflake-connector-python==3.15.0
snowflake-sqlalchemy==1.7.3

What did you do?

engine = sa.create_engine(...)
with engine.connect() as conn:
    result = conn.execute(sa.select(sa.literal(decimal.Decimal('1.3'))))
    resval = result.fetchone()
    assert resval == '1.3' # True - the SQL executed will be `SELECT '1.3'`, so it will return a string literal.

This is caused by:

snowflake-connector-python/src/snowflake/connector/converter.py

Lines 641 to 645 in 99bf619

	def _decimal_to_snowflake(self, value: decimal.Decimal) -> str | None:
	if isinstance(value, decimal.Decimal):
	return str(value)
	return None

What did you expect to see?

I expect this query to be executed as SELECT 1.3, not SELECT '1.3'. The bind parameter value of decimal.Decimal('1.3') is not being correctly rendered as a NUMBER contstant/literal. If the decimal.Decimal value was being correctly rendered during client-side parameter binding, then a numeric value (either float or, preferably decimal.Decimal) would be returned, not a str.

[sfc-gh-dszmolka]

hi @tboddyspargo - thanks for filing this issue. It indeed looks unexpected. The team will take a look - cannot promise a timeline though, it largely depends on the other issues. If this is critical to your business, please file it as a Support Case.