Hex¶

Overview¶

The Hex expression converts input values to their hexadecimal string representation. It accepts long integers, binary data, and strings, converting them to lowercase hexadecimal format. This is a deterministic, null-intolerant expression that preserves string collation types.

Syntax¶

HEX(expr)

hex(col("column_name"))

Arguments¶

Argument	Type	Description
child	Expression	The input expression to convert to hexadecimal format

Return Type¶

For string input: Returns the same StringType with preserved collation
For long and binary input: Returns StringType (default string producing behavior)

Supported Data Types¶

LongType - Long integers
BinaryType - Binary data (byte arrays)
StringType - String values (with trim collation support)

Algorithm¶

For LongType: Converts the long value directly to hexadecimal representation
For BinaryType: Converts each byte in the array to its hexadecimal equivalent
For StringType: First converts the string to UTF-8 bytes, then converts those bytes to hexadecimal
Uses static Hex.hex() methods for the actual conversion logic
Preserves the original string type and collation for string inputs

Partitioning Behavior¶

Preserves partitioning as it's a deterministic transformation
Does not require shuffle operations
Can be pushed down to individual partitions

Edge Cases¶

Null handling: Returns null for null inputs (null-intolerant behavior)
Empty strings: Converts empty strings to empty hexadecimal representation
Binary data: Handles empty byte arrays by producing empty hex strings
Long values: Handles negative long values according to two's complement representation

Code Generation¶

Supports Tungsten code generation through the doGenCode method. Uses nullSafeCodeGen to generate optimized bytecode that calls the static Hex.hex() methods directly, with special handling for string types that require byte conversion.

Examples¶

-- Convert string to hex
SELECT HEX('Spark SQL');
-- Result: 537061726B2053514C

-- Convert number to hex
SELECT HEX(255);
-- Result: FF

-- Convert binary data to hex
SELECT HEX(CAST('hello' AS BINARY));
-- Result: 68656C6C6F

// DataFrame API usage
import org.apache.spark.sql.functions._

df.select(hex(col("text_column")))
df.select(hex(col("binary_column")))
df.select(hex(col("long_column")))