Postgres Lag Window Function

boundary.sql

--Create boundaries at 30 minute timeout
select
uid,
event_timestamp,
(extract(epoch from event_timestamp) - lag(extract(epoch from event_timestamp)) OVER (PARTITION BY uid ORDER BY event_timestamp))/60 as minutes_since_last_interval,
case when extract(epoch from event_timestamp) - lag(extract(epoch from event_timestamp)) OVER (PARTITION BY uid ORDER BY event_timestamp) > 30 * 60 then 1 ELSE 0 END as new_event_boundary
from single_col_timestamp;