Module window_udf 

Window function UDFs (TUMBLE, HOP, SESSION, CUMULATE) Window function UDFs for DataFusion integration

Provides scalar UDFs that compute window start timestamps for streaming window operations:

• TumbleWindowStart — tumble(timestamp, interval) — fixed-size non-overlapping windows
• HopWindowStart — hop(timestamp, slide, size) — fixed-size overlapping windows
• SessionWindowStart — session(timestamp, gap) — pass-through for Ring 0 sessions

These UDFs allow DataFusion to execute GROUP BY TUMBLE(...) style queries by computing the window start as a per-row scalar value.

Structs

CumulateWindowStart

Computes the cumulate window epoch start for a given timestamp.

HopWindowStart

Computes the earliest hopping window start for a given timestamp.

SessionWindowStart

Pass-through UDF for session window compatibility.

TumbleWindowStart

Computes the tumbling window start for a given timestamp.