Module window 

Window Function Execution

This module implements window function execution for SQL queries.

Supports:

• ROW_NUMBER() - Sequential row numbering
• RANK() - Ranking with gaps
• DENSE_RANK() - Ranking without gaps
• NTILE(n) - Divides rows into n groups
• LEAD(col, offset, default) - Access next row’s value
• LAG(col, offset, default) - Access previous row’s value

Window clauses:

• OVER () - Entire result set as one partition
• OVER (PARTITION BY col) - Partition by column values
• OVER (ORDER BY col) - Order within partition

Structs

ColumnarOrderByValues

Columnar layout for ORDER BY values - optimized for sorting performance

SelectItem

Information about a SELECT list item for window function processing

WindowExecutor

Single owner for window planning, partition state, execution and result finalization. The host supplies only the immutable function registry.

WindowFunctionInfo

Information about a window function call in a SELECT list

WindowPreGroupedState

Pre-grouped state for window function PARTITION BY optimization When rows are fetched grouped by an indexed partition column, we can skip hash-based grouping

WindowPreSortedState

Pre-sorted state for window function optimization When rows are pre-sorted by an indexed column, we can skip sorting in window functions

Enums

SelectItemSource

Source of a SELECT item value

Traits

WindowExecutorExt

Compatibility surface used by the composition root while the surrounding SELECT orchestration is migrated.

WindowHost

Narrow composition contract required by window planning and execution.