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Author: themisvaltinos

sqlglot/generators/duckdb.py

@@ -655,6 +655,26 @@ def _struct_sql(self: DuckDBGenerator, expression: exp.Struct) -> str:
     return f"ROW({csv_args})" if is_bq_inline_struct else f"{{{csv_args}}}"
 
 
+def _big_decimal_sql(self: DuckDBGenerator, expression: exp.DataType) -> str:
+    if params := expression.expressions:
+        precision_param = params[0].this if isinstance(params[0], exp.DataTypeParam) else params[0]
+        if (
+            isinstance(precision_param, exp.Literal)
+            and precision_param.is_number
+            and int(precision_param.to_py()) > 38
+        ):
+            self.unsupported(
+                "DECIMAL precision exceeds maximum of 38 for DuckDB, capping to (38,5)"
+            )
+            expression = expression.copy()
+            expression.expressions[0].set("this", exp.Literal.number(38))
+            expression.expressions[1].set("this", exp.Literal.number(5))
+
+        return f"DECIMAL({self.expressions(expression, flat=True)})"
+
+    return "DECIMAL(38, 5)"
+
+
 def _datatype_sql(self: DuckDBGenerator, expression: exp.DataType) -> str:
     if expression.is_type("array"):
         return f"{self.expressions(expression, flat=True)}[{self.expressions(expression, key='values', flat=True)}]"
@@ -663,9 +683,8 @@ def _datatype_sql(self: DuckDBGenerator, expression: exp.DataType) -> str:
     if expression.is_type(exp.DType.TIME, exp.DType.TIMETZ, exp.DType.TIMESTAMPTZ):
         return expression.this.value
 
-    # BIGDECIMAL type maps to DECIMAL(38, 5) but we should pass through user params when provided
-    if expression.is_type(exp.DType.BIGDECIMAL) and expression.expressions:
-        return f"DECIMAL({self.expressions(expression, flat=True)})"
+    if expression.is_type(exp.DType.BIGDECIMAL):
+        return _big_decimal_sql(self, expression)
 
     return self.datatype_sql(expression)
 
@@ -1745,7 +1764,7 @@ class DuckDBGenerator(generator.Generator):
         exp.DType.TIMESTAMP_S: "TIMESTAMP_S",
         exp.DType.TIMESTAMP_MS: "TIMESTAMP_MS",
         exp.DType.TIMESTAMP_NS: "TIMESTAMP_NS",
-        exp.DType.BIGDECIMAL: "DECIMAL(38, 5)",
+        exp.DType.BIGDECIMAL: "DECIMAL",
     }
 
     # https://github.com/duckdb/duckdb/blob/ff7f24fd8e3128d94371827523dae85ebaf58713/third_party/libpg_query/grammar/keywords/reserved_keywords.list#L1-L77

tests/dialects/test_bigquery.py

@@ -3824,11 +3824,19 @@ def test_bignumeric(self):
                     },
                 )
 
+                self.validate_all(
+                    f"DECLARE x {type_}(20, 4)",
+                    write={
+                        "bigquery": "DECLARE x BIGNUMERIC(20, 4)",
+                        "duckdb": "DECLARE x DECIMAL(20, 4)",
+                    },
+                )
+
                 self.validate_all(
                     f"DECLARE x {type_}(76, 38)",
                     write={
                         "bigquery": "DECLARE x BIGNUMERIC(76, 38)",
-                        "duckdb": "DECLARE x DECIMAL(76, 38)",
+                        "duckdb": "DECLARE x DECIMAL(38, 5)",
                     },
                 )