GeneratorOuter¶

Overview¶

GeneratorOuter is a wrapper expression around another generator that specifies outer behavior for generator functions. It is primarily used to implement SQL functions like explode_outer and gets replaced during the analysis phase of query planning.

Syntax¶

-- Used internally to implement functions like:
SELECT explode_outer(array_column) FROM table_name

Arguments¶

Argument	Type	Description
child	Generator	The underlying generator expression to be wrapped with outer behavior

Return Type¶

Returns the same element schema as the wrapped child generator (StructType).

Supported Data Types¶

Supports any data types that the underlying child generator supports, as this is purely a wrapper expression.

Algorithm¶

Wraps an existing Generator expression to modify its behavior to outer semantics
Acts as a placeholder during query analysis and planning phases
Delegates element schema determination to the wrapped child generator
Gets replaced with appropriate implementation during analysis, never executed directly
Maintains the same structural properties as the underlying generator

Partitioning Behavior¶

Partitioning behavior depends entirely on the wrapped child generator since this expression is replaced during analysis:

Does not directly affect partitioning as it's not executed
Final partitioning behavior determined by the replacement expression created during analysis

Edge Cases¶

Cannot be evaluated directly - throws QueryExecutionErrors.cannotEvaluateExpressionError
Cannot generate code - throws QueryExecutionErrors.cannotGenerateCodeForExpressionError
Always reports as unresolved (resolved = false) to ensure analysis phase processing
Null handling depends on the replacement expression created during analysis

Code Generation¶

This expression does not support code generation and will throw an error if code generation is attempted, as it should be replaced during analysis before reaching the code generation phase.

Examples¶

-- This expression is used internally for:
SELECT explode_outer(ARRAY(1, 2, 3)) as value;
SELECT posexplode_outer(ARRAY('a', 'b')) as (pos, value);

// Internal usage during analysis phase
// Not directly accessible via DataFrame API
// Gets created when parsing outer generator functions