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feat(snowflake)!: Support transpilation of TO_DOUBLE from snowflake to duckdb #6658

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feat(snowflake)!: Support transpilation of TO_DOUBLE from snowflake to duckdb #6658

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fe965ca
support transpilation of to_double from snowflake to duckdb
fivetran-felixhuang Jan 5, 2026
25f3185
fix format
fivetran-felixhuang Jan 5, 2026
a8487fe
update name
fivetran-felixhuang Jan 7, 2026
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43 changes: 43 additions & 0 deletions sqlglot/dialects/duckdb.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1734,6 +1734,49 @@ def tobinary_sql(self: DuckDB.Generator, expression: exp.ToBinary) -> str:
# Fallback, which needs to be updated if want to support transpilation from other dialects than Snowflake
return self.func("TO_BINARY", value)

def todouble_sql(self, expression: exp.ToDouble) -> str:
"""
Transpile TO_DOUBLE to DuckDB with comprehensive format handling.

Handles Snowflake number format models by cleaning input strings based on format patterns.
"""
value = expression.this
format_arg = expression.args.get("format")

if format_arg and isinstance(format_arg, exp.Literal):
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@georgesittas georgesittas Jan 7, 2026

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Does this branch handle every format supported by Snowflake? It's quite complicated and so I'd like to understand if the complexity stems from it being a complete solution or just hacking it together.

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@fivetran-felixhuang fivetran-felixhuang Jan 7, 2026

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https://docs.snowflake.com/en/sql-reference/sql-format-models

This can handle the formats specified under the "Fixed-position numeric formats" section, except for Hexadecimal digit (I couldn't find a working example of it and thus can't test it). These formats are included in the test query shown above.

There are also Text-minimal numeric formats, and as far as I know they are just the default format for DOUBLE and DECIMAL

# Use REGEXP_REPLACE to remove commas, dollar signs, and spaces
cleaned_value = exp.func(
"REGEXP_REPLACE", value, exp.Literal.string(r"[,$\s]"), exp.Literal.string("")
)

# Handle trailing signs (MI and S formats) - move '+' or '-' from end to beginning
format_upper = format_arg.this.upper()
if "MI" in format_upper or "S" in format_upper:
cleaned_value = (
exp.case()
.when(
exp.func("RIGHT", cleaned_value, exp.Literal.number(1)).eq(
exp.Literal.string("-")
),
exp.func(
"CONCAT",
exp.Literal.string("-"),
exp.func("RTRIM", cleaned_value, exp.Literal.string("-")),
),
)
.when(
exp.func("RIGHT", cleaned_value, exp.Literal.number(1)).eq(
exp.Literal.string("+")
),
exp.func("RTRIM", cleaned_value, exp.Literal.string("+")),
)
.else_(cleaned_value)
)

value = cleaned_value

return self.sql(exp.cast(value, exp.DataType.Type.DOUBLE))

def _greatest_least_sql(
self: DuckDB.Generator, expression: exp.Greatest | exp.Least
) -> str:
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19 changes: 13 additions & 6 deletions tests/dialects/test_snowflake.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2339,17 +2339,24 @@ def test_sample(self):
},
)
self.validate_all(
"TO_DOUBLE(expr)",
"TO_DOUBLE('123.45')",
write={
"snowflake": "TO_DOUBLE(expr)",
"duckdb": "CAST(expr AS DOUBLE)",
"snowflake": "TO_DOUBLE('123.45')",
"duckdb": "CAST('123.45' AS DOUBLE)",
},
)
self.validate_all(
"TO_DOUBLE(expr, fmt)",
"TO_DOUBLE('$1,234.56', '$9,999.99')",
write={
"snowflake": "TO_DOUBLE(expr, fmt)",
"duckdb": UnsupportedError,
"snowflake": "TO_DOUBLE('$1,234.56', '$9,999.99')",
"duckdb": "CAST(REGEXP_REPLACE('$1,234.56', '[,$\s]', '', 'g') AS DOUBLE)",
},
)
self.validate_all(
"TO_DOUBLE('-4.56E-03', 'S9.99EEEE')",
write={
"snowflake": "TO_DOUBLE('-4.56E-03', 'S9.99EEEE')",
"duckdb": "CAST(CASE WHEN RIGHT(REGEXP_REPLACE('-4.56E-03', '[,$\s]', '', 'g'), 1) = '-' THEN '-' || RTRIM(REGEXP_REPLACE('-4.56E-03', '[,$\s]', '', 'g'), '-') WHEN RIGHT(REGEXP_REPLACE('-4.56E-03', '[,$\s]', '', 'g'), 1) = '+' THEN RTRIM(REGEXP_REPLACE('-4.56E-03', '[,$\s]', '', 'g'), '+') ELSE REGEXP_REPLACE('-4.56E-03', '[,$\s]', '', 'g') END AS DOUBLE)",
},
)

Expand Down