Merge pull request #53328 from valbok/decimal

Introduce default parameters to DECIMAL family types

docs/en/sql-reference/data-types/decimal.md

@@ -4,15 +4,17 @@ sidebar_position: 42
 sidebar_label: Decimal
 ---
 
-# Decimal(P, S), Decimal32(S), Decimal64(S), Decimal128(S), Decimal256(S)
+# Decimal, Decimal(P), Decimal(P, S), Decimal32(S), Decimal64(S), Decimal128(S), Decimal256(S)
 
 Signed fixed-point numbers that keep precision during add, subtract and multiply operations. For division least significant digits are discarded (not rounded).
 
 ## Parameters
 
-- P - precision. Valid range: \[ 1 : 76 \]. Determines how many decimal digits number can have (including fraction).
+- P - precision. Valid range: \[ 1 : 76 \]. Determines how many decimal digits number can have (including fraction). By default the precision is 10.
 - S - scale. Valid range: \[ 0 : P \]. Determines how many decimal digits fraction can have.
 
+Decimal(P) is equivalent to Decimal(P, 0). Similarly, the syntax Decimal is equivalent to Decimal(10, 0).
+
 Depending on P parameter value Decimal(P, S) is a synonym for:
 - P from \[ 1 : 9 \] - for Decimal32(S)
 - P from \[ 10 : 18 \] - for Decimal64(S)

src/DataTypes/DataTypesDecimal.cpp

@@ -74,21 +74,30 @@ SerializationPtr DataTypeDecimal<T>::doGetDefaultSerialization() const
 
 static DataTypePtr create(const ASTPtr & arguments)
 {
-    if (!arguments || arguments->children.size() != 2)
-        throw Exception(ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH,
-                        "Decimal data type family must have exactly two arguments: precision and scale");
+    UInt64 precision = 10;
+    UInt64 scale = 0;
+    if (arguments)
+    {
+        if (arguments->children.empty() || arguments->children.size() > 2)
+            throw Exception(
+                ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH,
+                "Decimal data type family must have precision and optional scale arguments");
 
-    const auto * precision = arguments->children[0]->as<ASTLiteral>();
-    const auto * scale = arguments->children[1]->as<ASTLiteral>();
+        const auto * precision_arg = arguments->children[0]->as<ASTLiteral>();
+        if (!precision_arg || precision_arg->value.getType() != Field::Types::UInt64)
+            throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Decimal argument precision is invalid");
+        precision = precision_arg->value.get<UInt64>();
 
-    if (!precision || precision->value.getType() != Field::Types::UInt64 ||
-        !scale || !(scale->value.getType() == Field::Types::Int64 || scale->value.getType() == Field::Types::UInt64))
-        throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Decimal data type family must have two numbers as its arguments");
+        if (arguments->children.size() == 2)
+        {
+            const auto * scale_arg = arguments->children[1]->as<ASTLiteral>();
+            if (!scale_arg || !isInt64OrUInt64FieldType(scale_arg->value.getType()))
+                throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Decimal argument scale is invalid");
+            scale = scale_arg->value.get<UInt64>();
+        }
+    }
 
-    UInt64 precision_value = precision->value.get<UInt64>();
-    UInt64 scale_value = scale->value.get<UInt64>();
-
-    return createDecimal<DataTypeDecimal>(precision_value, scale_value);
+    return createDecimal<DataTypeDecimal>(precision, scale);
 }
 
 template <typename T>

tests/queries/0_stateless/00700_decimal_with_default_precision_and_scale.reference

@@ -0,0 +1,4 @@
+Decimal(9, 8)
+Decimal(18, 0)
+Decimal(10, 0)
+Decimal(18, 0)	Decimal(10, 0)

tests/queries/0_stateless/00700_decimal_with_default_precision_and_scale.sql

@@ -0,0 +1,19 @@
+DROP TABLE IF EXISTS decimal;
+
+CREATE TABLE IF NOT EXISTS decimal
+(
+    d1 DECIMAL(9, 8),
+    d2 DECIMAL(18),
+    d3 DECIMAL
+)
+ENGINE = MergeTree
+PARTITION BY toInt32(d1)
+ORDER BY (d2, d3);
+
+INSERT INTO decimal (d1, d2, d3) VALUES (4.2, 4.2, 4.2);
+
+SELECT type FROM system.columns WHERE table = 'decimal' AND database = currentDatabase();
+
+SELECT toTypeName(d2), toTypeName(d3) FROM decimal LIMIT 1;
+
+DROP TABLE decimal;