Module window 

Window Functions Executor

Provides SQL standard window functions for analytical queries.

Window Function Types

Ranking Functions:

• ROW_NUMBER(): Sequential number within partition
• RANK(): Rank with gaps for ties
• DENSE_RANK(): Rank without gaps for ties
• NTILE(n): Divide partition into n buckets
• PERCENT_RANK(): Relative rank as percentage
• CUME_DIST(): Cumulative distribution

Value Functions:

• FIRST_VALUE(x): First value in frame
• LAST_VALUE(x): Last value in frame
• NTH_VALUE(x, n): Nth value in frame
• LAG(x, n, default): Value n rows before current
• LEAD(x, n, default): Value n rows after current

Aggregate Functions (with OVER):

• All standard aggregates (SUM, AVG, COUNT, MIN, MAX, etc.)

Frame Specification

Frames define the subset of partition rows for each computation:

• ROWS: Physical row-based boundaries
• RANGE: Value-based logical boundaries
• GROUPS: Groups of peer rows

Implementation

Window functions are evaluated in three phases:

1. Partition: Group rows by PARTITION BY columns
2. Order: Sort each partition by ORDER BY columns
3. Compute: Apply window function with frame for each row

Structs

FrameSpec

Frame specification for window function

WindowDef

Complete window definition

WindowExecutor

Window function executor

WindowFunc

A window function to apply

WindowOrderBy

Order-by specification for window

Enums

FrameBound

Frame boundary specification

FrameExclude

Frame exclusion option

FrameType

Frame type for window functions

NullsOrder

Null handling in sorting

SortDirection

Sort direction

WindowFuncType

Type of window function