mirabilos authored 5 years ago and mirabilos committed 5 years ago

Should cut SQL queries for lessons about into half.

mirabilos authored 5 years ago and mirabilos committed 5 years ago

This is correct performance-wise (avoids the need for the database to
build the entire result set before filtering; Django users reported a
speed-up of factor 5‥2000 over naïve solutions) and (accepted by Nik)
even more legible.

This reverts commit b9a8c04e.