This reverts commit ad4beac464f6275bf78ce5b8d6958d9e7f232f36.
That commit wasn't as advertised; I had several other changes mixed in my
working copy. I'd also copied a working copy from one path to another, and
it turns out the cmake build subdir was still referring to the original, so
I hadn't realized this commit didn't even build. :(
* Schema revisions. The most dramatic is the addition of a covering index on
(camera_id, start_time_90k) that avoids the need to make sparse accesses
into the recording table (where the desired data is intermixed with both
the large blobs and rows from other cameras). A query over a year's data
previously took many seconds (6+ even in a form without the video_index)
and now is roughly 10X faster. Queries for a couple weeks now should be
unnoticeably fast.
Other changes to shrink the rows, such as duration_90k instead of
end_time_90k (more compact varint encoding) and video_sample_entry_id
(typically 1 byte) instead of video_sample_entry_sha1 (20 bytes).
And more CHECK constraints for good measure.
* Caching of expensive computations and logic to keep them up to date.
The top-level web view previously went through the entire recording table,
which was even slower. Now it is served from a small map in RAM.
* Expanded the scope of operations to cover (hopefully) everything needed for
recording into the SQLite database.
* Added tests of MoonfireDatabase. These are basic tests that don't
exercise a lot of error cases, but at least they exist.
The main MoonfireDatabase functionality still missing is support for quickly
seeing what calendar days have data over the full timespan of a camera. This
is more data to compute and cache.
This is almost certain to have performance problems with large databases,
but it's a useful starting point.
No tests yet. It shouldn't be too hard to add some for moonfire-db.h, but
I'm impatient to fake up enough data to check on the performance and see
what needs to change there first.
