Retrieving the most recent record with skip scan is easy enough, but how do I get the timestamp of the previous record as well?

Hello, I am using TSDB and want to get a set of most recent records. I only see good performance if I structure my query like so, and this shows that skip scan is being used when I run EXPLAIN ANALYZE

Planning Time: 0.777 ms
Execution Time: 10.287 ms

WITH updated_widgets AS (
    SELECT w.id
    FROM widgets AS w
    WHERE w.dirty = 1
), widget_data AS (
    SELECT DISTINCT ON (w.id) wd.*
    FROM "widget_data"  AS wd
    ORDER BY wd.mac_address, wd.time DESC
)
SELECT * FROM widget_data
WHERE wd.id IN (SELECT id FROM updated_widgets);

This is very fast. Skip scan would not trigger if I added a WHERE clause or JOIN clause, but it appears to work with a CTE.

Here’s the current issue…I need a window where I can perform some calculations using the most recent record for each widget pulled from widget data AND the record prior to that. Skip scan does not trigger if I use LAG like so:

Planning Time: 0.420 ms
Execution Time: 13079.934 ms

 widget_data AS (
    SELECT DISTINCT ON (w.id)
      wd.time,
     LAG(wd.time, 1) OVER (ORDER BY wd.time DESC) AS prev_time
    FROM "widget_data"  AS wd
    ORDER BY wd.mac_address, wd.time DESC
)

How can I get the current record AND the previous record while using skip scan? Is this even possible?

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