Chr¶

Overview¶

The Chr expression converts a numeric value to its corresponding ASCII character representation. It takes a long integer input and returns a single-character string based on the lowest 8 bits of the input value, effectively implementing ASCII character code conversion.

Syntax¶

CHR(numeric_expression)

chr(col("column_name"))

Arguments¶

Argument	Type	Description
child	Long	The numeric value to convert to an ASCII character (automatically cast to LongType)

Return Type¶

UTF8String - A single character string or empty string

Supported Data Types¶

Numeric types that can be implicitly cast to LongType
The expression uses ImplicitCastInputTypes to automatically convert input to Long

Algorithm¶

Extract the input long value from the child expression
If the input is negative, return an empty UTF8String
If the lowest 8 bits equal zero (value & 0xFF == 0), return the MIN_VALUE character
Otherwise, mask the input with 0xFF to get the lowest 8 bits and convert to character
Convert the resulting character to a UTF8String

Partitioning Behavior¶

Preserves partitioning as it performs row-level transformation without requiring data movement
Does not require shuffle operations
Can be evaluated independently on each partition

Edge Cases¶

Null handling: Returns null if input is null (nullIntolerant = true)
Negative values: Returns empty string for any negative input
Zero byte values: Returns Character.MIN_VALUE when (input & 0xFF) == 0
Large values: Only uses the lowest 8 bits, so values > 255 are truncated
Out of ASCII range: Values are masked to 0-255 range using bitwise AND operation

Code Generation¶

This expression supports Tungsten code generation through the doGenCode method, generating optimized Java bytecode for runtime execution rather than falling back to interpreted mode.

Examples¶

SELECT CHR(65) AS letter;  -- Returns 'A'
SELECT CHR(97) AS letter;  -- Returns 'a'
SELECT CHR(-1) AS letter;  -- Returns ''
SELECT CHR(321) AS letter; -- Returns 'A' (321 & 0xFF = 65)

import org.apache.spark.sql.functions.expr

df.select(expr("CHR(65)").as("letter"))
df.withColumn("ascii_char", expr("CHR(ascii_code_column)"))