Round¶

Overview¶

The Round expression rounds a numeric value to a specified number of decimal places using the HALF_UP rounding mode. It extends RoundBase and provides rounding functionality with configurable scale and ANSI SQL compliance support.

Syntax¶

ROUND(expr [, scale])

round(col("column_name"), scale)

Arguments¶

Argument	Type	Description
child	Expression	The numeric expression to be rounded
scale	Expression	The number of decimal places to round to (defaults to 0)
ansiEnabled	Boolean	Whether ANSI SQL compliance is enabled (defaults to SQLConf setting)

Return Type¶

Returns the same numeric data type as the input expression (preserves input type).

Supported Data Types¶

Decimal types
Float and Double
Byte, Short, Integer, Long
Any numeric type that can be converted to BigDecimal

Algorithm¶

Converts the input value to BigDecimal for precision handling
Applies HALF_UP rounding mode (rounds 0.5 up to the next integer)
Scales the result to the specified number of decimal places
Returns the rounded value in the original data type
Handles ANSI mode for strict error handling on overflow/underflow

Partitioning Behavior¶

How this expression affects partitioning:

Preserves partitioning as it's a deterministic row-level transformation
Does not require shuffle operations
Can be applied within partition boundaries

Edge Cases¶

Null input returns null (null-safe operation)
Negative scale values round to the left of decimal point (e.g., scale=-1 rounds to tens)
Zero scale rounds to nearest integer
ANSI mode affects overflow/underflow error handling behavior
Very large scale values may cause precision issues

Code Generation¶

This expression supports Catalyst code generation (Tungsten) through its RoundBase parent class, enabling optimized bytecode generation for improved performance in tight loops.

Examples¶

-- Round to nearest integer
SELECT ROUND(3.7) -- Returns 4

-- Round to 2 decimal places  
SELECT ROUND(3.14159, 2) -- Returns 3.14

-- Round to tens place
SELECT ROUND(123.45, -1) -- Returns 120

// Round to nearest integer
df.select(round(col("price")))

// Round to 2 decimal places
df.select(round(col("price"), lit(2)))

// Using in withColumn
df.withColumn("rounded_price", round(col("price"), lit(2)))