RoundFloor¶

Overview¶

The RoundFloor expression performs rounding of a decimal number to a specified scale using the FLOOR rounding mode. It always rounds down towards negative infinity, truncating any digits beyond the specified decimal places.

Syntax¶

ROUND_FLOOR(value, scale)

// DataFrame API usage would typically be through built-in functions

Arguments¶

Argument	Type	Description
child	DecimalType	The decimal value to be rounded
scale	IntegerType	The number of decimal places to round to

Return Type¶

Returns a decimal value with the same precision characteristics as the input, rounded according to the FLOOR rounding mode.

Supported Data Types¶

Input: DecimalType for the value, IntegerType for the scale parameter
Output: DecimalType

Algorithm¶

Takes the input decimal value and scale parameter
Applies BigDecimal.RoundingMode.FLOOR rounding mode
Rounds the value to the specified number of decimal places
Always rounds towards negative infinity (down)
Inherits core rounding logic from the RoundBase parent class

Partitioning Behavior¶

How this expression affects partitioning:

Preserves partitioning as it's a deterministic row-level transformation
Does not require shuffle operations
Can be safely pushed down in query optimization

Edge Cases¶

Null handling: If either child or scale is null, the result is null
Negative scale: Rounds to positions left of the decimal point when scale is negative
Zero scale: Rounds to the nearest integer using FLOOR mode
Precision limits: Respects decimal precision and scale constraints of the Spark DecimalType system

Code Generation¶

This expression extends RoundBase which typically supports Tungsten code generation for optimal performance in the Catalyst query engine, avoiding interpreted evaluation overhead.

Examples¶

-- Round 3.7 down to nearest integer
SELECT ROUND_FLOOR(3.7, 0); -- Returns 3

-- Round 3.14159 down to 2 decimal places  
SELECT ROUND_FLOOR(3.14159, 2); -- Returns 3.14

-- Round negative number down
SELECT ROUND_FLOOR(-2.3, 0); -- Returns -3

// Example would use Catalyst expression directly
val roundFloor = RoundFloor(
  child = Literal(Decimal(3.14159)), 
  scale = Literal(2)
)