ny_times_us_counties needs a "date desc" index

[simonw]

When you paginate through the https://covid-19.datasettes.com/covid/ny_times_us_counties table - which now has more than 1.3m records - each page takes ~200ms to query. It's sorted by date, descending with an index on date.

With an index on date desc instead each page only takes ~10ms.

[simonw]

Before deploying this change, https://covid-19.datasettes.com/covid?sql=select+*+from+pragma_index_xinfo%28%27idx_ny_times_us_counties_date%27%29 returns:

seqno	cid	name	desc	coll	key
0	0	date	0	BINARY	1
1	-1		0	BINARY	0

[simonw]

And now:

seqno	cid	name	desc	coll	key
0	0	date	1	BINARY	1
1	-1		0	BINARY	0

[simonw]

Turns out that wasn't the cause of the performance problem after all! simonw/datasette#1349