Module window 

Window Function Evaluator

This module implements the core window function evaluation engine that:

• Partitions rows by PARTITION BY expressions
• Sorts partitions by ORDER BY clauses
• Calculates frame boundaries (ROWS mode)
• Evaluates window functions over frames

Module Organization

The window function evaluator is split into logical modules:

• partitioning - Partition management and row grouping
• sorting - Partition sorting and value comparison
• frames - Frame boundary calculation (ROWS mode)
• ranking - Ranking functions (ROW_NUMBER, RANK, DENSE_RANK, NTILE)
• aggregates - Aggregate window functions (COUNT, SUM, AVG, MIN, MAX)
• value - Value access functions (LAG, LEAD, FIRST_VALUE, LAST_VALUE)
• utils - Shared utility functions

Structs

FrameResult

Result of frame calculation including exclusion information

Partition

A partition of rows for window function evaluation

Functions

calculate_frame

Calculate frame boundaries for a given row in a partition

calculate_frame_with_exclusion

Calculate frame with exclusion information

compare_values

Compare two SQL values for ordering

evaluate_avg_window

Evaluate AVG aggregate window function over a frame

evaluate_count_window

Evaluate COUNT aggregate window function over a frame

evaluate_cume_dist

Evaluate CUME_DIST() window function

evaluate_dense_rank

Evaluate DENSE_RANK() window function

evaluate_first_value

Evaluate FIRST_VALUE() value window function

evaluate_group_concat_window

Evaluate GROUP_CONCAT aggregate window function over a frame

evaluate_lag

Evaluate LAG() value window function

evaluate_last_value

Evaluate LAST_VALUE() value window function

evaluate_lead

Evaluate LEAD() value window function

evaluate_max_window

Evaluate MAX aggregate window function over a frame

evaluate_min_window

Evaluate MIN aggregate window function over a frame

evaluate_nth_value

Evaluate NTH_VALUE() value window function

evaluate_ntile

Evaluate NTILE(n) window function

evaluate_percent_rank

Evaluate PERCENT_RANK() window function

evaluate_rank

Evaluate RANK() window function

evaluate_row_number

Evaluate ROW_NUMBER() window function

evaluate_sum_window

Evaluate SUM aggregate window function over a frame

partition_rows

Partition rows by PARTITION BY expressions

sort_partition

Sort a partition by ORDER BY clauses

validate_frame

Validate a window frame specification, returning an error if invalid.