UnresolvedWindowExpression¶

Overview¶

UnresolvedWindowExpression is an intermediate expression used during Catalyst's analysis phase to represent window functions that have not yet been resolved with their specific window specifications. It serves as a placeholder that gets transformed into concrete window expressions during the resolution process.

Syntax¶

This expression is not directly used in SQL or DataFrame API - it's an internal Catalyst representation created during parsing and analysis phases.

Arguments¶

Argument	Type	Description
child	Expression	The window function expression to be applied
windowSpec	WindowSpecReference	Reference to the window specification defining partitioning, ordering, and frame bounds

Return Type¶

Cannot determine return type - throws UnresolvedException when dataType is accessed, as the actual data type depends on the resolved child expression.

Supported Data Types¶

Not applicable - this expression cannot be evaluated and serves only as a placeholder during analysis. The supported data types depend on the underlying child expression after resolution.

Algorithm¶

Acts as a wrapper around an unresolved window function during Catalyst analysis
Maintains reference to both the function expression and window specification
Throws UnresolvedException for any evaluation-related operations
Gets replaced by concrete window expressions during the resolution phase
Implements Unevaluable trait to prevent direct evaluation attempts

Partitioning Behavior¶

Not applicable during the unresolved state: - Partitioning behavior depends on the resolved window expression - Window specifications may define partitioning requirements - Actual shuffle requirements determined after resolution

Edge Cases¶

Evaluation attempts: Throws UnresolvedException for dataType and nullable access
Resolution status: Always returns false for resolved property
Analysis failures: May cause analysis exceptions if window specification cannot be resolved
Invalid references: Fails if windowSpec references non-existent window definitions

Code Generation¶

Not applicable - this expression cannot generate code as it implements Unevaluable. Code generation occurs only after resolution into concrete window expressions.

Examples¶

-- This SQL would create UnresolvedWindowExpression internally:
SELECT sum(value) OVER w FROM table
WINDOW w AS (PARTITION BY id ORDER BY timestamp)

// Internal representation (not user-facing):
UnresolvedWindowExpression(
  child = UnresolvedFunction("sum", Seq(col("value"))),
  windowSpec = WindowSpecReference("w")
)