CurrentTimeZone¶

Overview¶

The CurrentTimeZone expression returns the current session time zone as a string. This is a non-deterministic expression that retrieves the time zone setting for the current Spark session without requiring any input parameters.

Syntax¶

SELECT current_timezone();

// DataFrame API
import org.apache.spark.sql.functions._
df.select(expr("current_timezone()"))

Arguments¶

Argument	Type	Description
None	N/A	This expression takes no arguments

Return Type¶

StringType - Returns the time zone identifier as a string (e.g., "Asia/Shanghai", "UTC").

Supported Data Types¶

This expression does not accept input data types as it is a leaf expression with no parameters.

Algorithm¶

Retrieves the current session's time zone configuration
Returns the time zone identifier as a string representation
Operates as a leaf expression in the Catalyst expression tree
Extends Unevaluable trait, indicating special evaluation handling
Uses DefaultStringProducingExpression for consistent string output behavior

Partitioning Behavior¶

This expression has minimal impact on partitioning:

Preserves existing partitioning as it generates the same value across all partitions
Does not require shuffle operations
Can be safely used in partitioned operations without affecting data distribution

Edge Cases¶

Never returns null values (nullable = false)
Always returns a valid time zone string based on session configuration
Behavior is consistent within a single session but may vary across different sessions
No overflow or underflow conditions as it returns configuration data

Code Generation¶

This expression extends Unevaluable, which means it does not support standard Tungsten code generation and falls back to interpreted evaluation mode during query execution.

Examples¶

-- Get current session timezone
SELECT current_timezone();
-- Result: Asia/Shanghai

-- Use in a query with other datetime functions
SELECT current_timestamp(), current_timezone();

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

// Add timezone column to existing DataFrame
df.withColumn("session_tz", expr("current_timezone()"))

// Select timezone with other columns
df.select($"id", expr("current_timezone()").as("timezone"))