feat(duckdb)!: handle named arguments and non-integer scale input for ROUND (#6495)

* support named arguments and non-integer scale values

* remove

* unpack Kwargs at Snowflake parse time + address other Kwarg feedback

Author: toriwei

sqlglot/dialects/duckdb.py

@@ -1605,6 +1605,15 @@ def round_sql(self, expression: exp.Round) -> str:
             decimals = expression.args.get("decimals")
             truncate = expression.args.get("truncate")
 
+            # DuckDB requires the scale (decimals) argument to be an INT
+            # Some dialects (e.g., Snowflake) allow non-integer scales and cast to an integer internally
+            if decimals is not None and expression.args.get("casts_non_integer_decimals"):
+                if isinstance(decimals, exp.Literal):
+                    if not decimals.is_int:
+                        decimals = exp.cast(decimals, exp.DataType.Type.INT)
+                elif not decimals.is_type(*exp.DataType.INTEGER_TYPES):
+                    decimals = exp.cast(decimals, exp.DataType.Type.INT)
+
             func = "ROUND"
             if truncate:
                 # BigQuery uses ROUND_HALF_EVEN; Snowflake uses HALF_TO_EVEN

sqlglot/dialects/snowflake.py

@@ -550,6 +550,36 @@ def _build_timestamp_from_parts(args: t.List) -> exp.Func:
     return exp.TimestampFromParts.from_arg_list(args)
 
 
+def _build_round(args: t.List) -> exp.Round:
+    """
+    Build Round expression, unwrapping Snowflake's named parameters.
+
+    Maps EXPR => this, SCALE => decimals, ROUNDING_MODE => truncate.
+
+    Note: Snowflake does not support mixing named and positional arguments.
+    Arguments are either all named or all positional.
+    """
+    kwarg_map = {"EXPR": "this", "SCALE": "decimals", "ROUNDING_MODE": "truncate"}
+    round_args = {}
+    positional_keys = ["this", "decimals", "truncate"]
+    positional_idx = 0
+
+    for arg in args:
+        if isinstance(arg, exp.Kwarg):
+            key = arg.this.name.upper()
+            round_key = kwarg_map.get(key)
+            if round_key:
+                round_args[round_key] = arg.expression
+        else:
+            if positional_idx < len(positional_keys):
+                round_args[positional_keys[positional_idx]] = arg
+                positional_idx += 1
+
+    expression = exp.Round(**round_args)
+    expression.set("casts_non_integer_decimals", True)
+    return expression
+
+
 class Snowflake(Dialect):
     # https://docs.snowflake.com/en/sql-reference/identifiers-syntax
     NORMALIZATION_STRATEGY = NormalizationStrategy.UPPERCASE
@@ -717,6 +747,7 @@ class Parser(parser.Parser):
             "REGEXP_SUBSTR_ALL": _build_regexp_extract(exp.RegexpExtractAll),
             "REPLACE": build_replace_with_optional_replacement,
             "RLIKE": exp.RegexpLike.from_arg_list,
+            "ROUND": _build_round,
             "SHA1_BINARY": exp.SHA1Digest.from_arg_list,
             "SHA1_HEX": exp.SHA.from_arg_list,
             "SHA2_BINARY": exp.SHA2Digest.from_arg_list,

sqlglot/expressions.py

@@ -7727,7 +7727,12 @@ class Radians(Func):
 # https://learn.microsoft.com/en-us/sql/t-sql/functions/round-transact-sql?view=sql-server-ver16
 # tsql third argument function == trunctaion if not 0
 class Round(Func):
-    arg_types = {"this": True, "decimals": False, "truncate": False}
+    arg_types = {
+        "this": True,
+        "decimals": False,
+        "truncate": False,
+        "casts_non_integer_decimals": False,
+    }
 
 
 class RowNumber(Func):

tests/dialects/test_duckdb.py

@@ -1253,6 +1253,7 @@ def test_duckdb(self):
         )
         self.validate_identity("SELECT GREATEST(1.0, 2.5, NULL, 3.7)")
         self.validate_identity("FROM t1, t2 SELECT *", "SELECT * FROM t1, t2")
+        self.validate_identity("ROUND(2.256, 1)")
 
         # TODO: This is incorrect AST, DATE_PART creates a STRUCT of values but it's stored in 'year' arg
         self.validate_identity("SELECT MAKE_DATE(DATE_PART(['year', 'month', 'day'], TODAY()))")

tests/dialects/test_snowflake.py

@@ -3712,6 +3712,22 @@ def test_round(self):
             },
         )
 
+        self.validate_all(
+            "SELECT ROUND(EXPR => 2.25, SCALE => 1) AS value",
+            write={
+                "snowflake": "SELECT ROUND(2.25, 1) AS value",
+                "duckdb": "SELECT ROUND(2.25, 1) AS value",
+            },
+        )
+
+        self.validate_all(
+            "SELECT ROUND(SCALE => 1, EXPR => 2.25) AS value",
+            write={
+                "snowflake": "SELECT ROUND(2.25, 1) AS value",
+                "duckdb": "SELECT ROUND(2.25, 1) AS value",
+            },
+        )
+
         self.validate_all(
             "SELECT ROUND(2.25, 1, 'HALF_AWAY_FROM_ZERO') AS value",
             write={
@@ -3720,10 +3736,58 @@ def test_round(self):
             },
         )
 
+        self.validate_all(
+            "SELECT ROUND(EXPR => 2.25, SCALE => 1, ROUNDING_MODE => 'HALF_AWAY_FROM_ZERO') AS value",
+            write={
+                "snowflake": "SELECT ROUND(2.25, 1, 'HALF_AWAY_FROM_ZERO') AS value",
+                "duckdb": "SELECT ROUND(2.25, 1) AS value",
+            },
+        )
+
         self.validate_all(
             "SELECT ROUND(2.25, 1, 'HALF_TO_EVEN') AS value",
             write={
-                "snowflake": """SELECT ROUND(2.25, 1, 'HALF_TO_EVEN') AS value""",
+                "snowflake": "SELECT ROUND(2.25, 1, 'HALF_TO_EVEN') AS value",
+                "duckdb": "SELECT ROUND_EVEN(2.25, 1) AS value",
+            },
+        )
+
+        self.validate_all(
+            "SELECT ROUND(ROUNDING_MODE => 'HALF_TO_EVEN', EXPR => 2.25, SCALE => 1) AS value",
+            write={
+                "snowflake": "SELECT ROUND(2.25, 1, 'HALF_TO_EVEN') AS value",
+                "duckdb": "SELECT ROUND_EVEN(2.25, 1) AS value",
+            },
+        )
+
+        self.validate_all(
+            "SELECT ROUND(SCALE => 1, EXPR => 2.25, , ROUNDING_MODE => 'HALF_TO_EVEN') AS value",
+            write={
+                "snowflake": "SELECT ROUND(2.25, 1, 'HALF_TO_EVEN') AS value",
+                "duckdb": "SELECT ROUND_EVEN(2.25, 1) AS value",
+            },
+        )
+
+        self.validate_all(
+            "SELECT ROUND(EXPR => 2.25, SCALE => 1, ROUNDING_MODE => 'HALF_TO_EVEN') AS value",
+            write={
+                "snowflake": "SELECT ROUND(2.25, 1, 'HALF_TO_EVEN') AS value",
                 "duckdb": "SELECT ROUND_EVEN(2.25, 1) AS value",
             },
         )
+
+        self.validate_all(
+            "SELECT ROUND(2.256, 1.8) AS value",
+            write={
+                "snowflake": "SELECT ROUND(2.256, 1.8) AS value",
+                "duckdb": "SELECT ROUND(2.256, CAST(1.8 AS INT)) AS value",
+            },
+        )
+
+        self.validate_all(
+            "SELECT ROUND(2.256, CAST(1.8 AS DECIMAL(38, 0))) AS value",
+            write={
+                "snowflake": "SELECT ROUND(2.256, CAST(1.8 AS DECIMAL(38, 0))) AS value",
+                "duckdb": "SELECT ROUND(2.256, CAST(CAST(1.8 AS DECIMAL(38, 0)) AS INT)) AS value",
+            },
+        )