Calculating the average on startup is expensive on mobile devices. It might be
nice to provide it as a deck option or per-model setting in the future so that
people can specify how hard their material is and have it treated accordingly.
Previously we had an index on the value field, which was very expensive for
long fields. Instead we use a separate column and take the first 8 characters
of the field value's md5sum, and index that. In decks with lots of text in
fields, it can cut the deck size by 30% or more, and many decks improve by
10-20%. Decks with only a few characters in fields may increase in size
slightly, but this is offset by the fact that we only generate a checksum for
fields that have uniqueness checking on.
Also, fixed import->update reporting the total # of available facts instead of
the number of facts that were imported.
Anki 1.0 had a similar feature but we do things a bit differently now. The
relative spacing applies only to reviews, and spaces cards according to their
interval, instead of spacing all cards the same. Any delay < 1 full day is
treated as no delay, so with the default 10% setting, reviews with an interval
< 10 days are not spaced at all. This should hopefully cut down on support
queries for people wondering why many of their cards were delayed, allows the
two settings to be documented separately, and does away with the somewhat
confusing usage of non-integer new sibling values to disable review spacing.
- this fixes a state where cards failed on that future day could end up
with an earlier due date that the rest of the failed mature cards, leading
to the newly failed cards being repeated prematurely
- this leads to non-deterministic scheduling of the mature bonus fails, so
they are effectively randomized which is probably what most users want
