UrlDecode¶

Overview¶

The UrlDecode expression decodes URL-encoded strings by converting percent-encoded characters back to their original form. This expression is implemented as a runtime replaceable expression that delegates to the UrlCodec.decode method with configurable error handling behavior.

Syntax¶

url_decode(url_string)
url_decode(url_string, fail_on_error)

// DataFrame API
col("url_column").expr("url_decode(url_column)")

Arguments¶

Argument	Type	Description
child	StringType	The URL-encoded string to decode
failOnError	Boolean	Whether to fail on malformed input (default: true)

Return Type¶

Returns StringType - the decoded URL string.

Supported Data Types¶

StringType with collation support (supports trim collation)
Input must be a valid string expression

Algorithm¶

Delegates processing to UrlCodec.decode through StaticInvoke
Uses runtime replacement pattern for code generation optimization
Applies percent-decoding to convert encoded characters (e.g., %20 → space)
Error handling behavior controlled by failOnError parameter
Supports collation-aware string processing with trim collation support

Partitioning Behavior¶

This expression preserves partitioning:

Does not require data shuffle as it operates on individual string values
Can be applied per-partition independently
Does not affect partition keys or distribution

Edge Cases¶

Null input returns null output (standard null propagation)
Empty string input returns empty string
Malformed percent-encoding behavior depends on failOnError flag
When failOnError is true, invalid encoding throws exception
When failOnError is false, invalid sequences may be left unchanged or handled gracefully
Supports trim collation for string comparison operations

Code Generation¶

This expression supports Tungsten code generation:

Implemented as RuntimeReplaceable for efficient code generation
Generates direct calls to UrlCodec.decode static method
Avoids interpreted expression evaluation overhead
Optimized through Catalyst's code generation framework

Examples¶

-- Basic URL decoding
SELECT url_decode('Hello%20World') AS decoded;
-- Result: "Hello World"

-- Decode with error handling
SELECT url_decode('user%40domain.com', true) AS email;  
-- Result: "user@domain.com"

-- Decode complex URL parameters
SELECT url_decode('param%3Dvalue%26other%3D123') AS params;
-- Result: "param=value&other=123"

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

df.select(expr("url_decode(encoded_url)").as("decoded"))

// With explicit error handling
df.select(expr("url_decode(encoded_url, false)").as("decoded"))