The approach of using incrementing id numbers works for syncing if we assume
the server is canonical and all other clients rewrite their ids as necessary,
but upon reflection it is not sufficient for merging decks in general, as we
have no way of knowing whether objects with the same id are actually the same
or not. So we need some way of uniquely identifying the object.
One approach would be to go back to Anki 1.0's random 64bit numbers, but as
outlined in a previous commit such large numbers can't be handled easy in some
languages like Javascript, and they tend to be fragmented on disk which
impacts performance. It's much better if we can keep content added at the same
time in the same place on disk, so that operations like syncing which are mainly
interested in newly added content can run faster.
Another approach is to add a separate column containing the unique id, which
is what Mnemosyne 2.0 will be doing. Unfortunately it means adding an index
for that column, leading to slower inserts and larger deck files. And if the
current sequential ids are kept, a bunch of code needs to be kept to ensure ids
don't conflict when merging.
To address the above, the plan is to use a millisecond timestamp as the id.
This ensures disk order reflects creation order, allows us to merge the id and
crt columns, avoids the need for a separate index, and saves us from worrying
about rewriting ids. There is of course a small chance that the objects to be
merged were created at exactly the same time, but this is extremely unlikely.
This commit changes models. Other objects will follow.
- rename to revlog
- change the pk to time, as we want an index on time, and the old multi-column
index was expensive and not useful
- remove yes/no count; they can be inferred from the ease
- remove lastFactor, as it's in the previous entry
- remove delay, it can be inferred from last entry
- remove 'next' from nextInterval and nextFactor
- rename 'thinkingTime' to 'userTime'
- rename reps to rep
- migrate old data to new table, and fix some problems in the process: ease0
-> ease1, and limit thinking time to 60 seconds as it should have been
previously
The stats table was how the early non-SQL versions of Anki kept track of
statistics, before there was a revision log. It is being removed because:
- it's not possible to show the statistics for a subset of the deck
- it can't meaningfully be copied on import/export
- it makes it harder to implement sync merging
Implications:
- graphs and deck stats roughly 1.5-3x longer than before, but we'll have the
ability to generate stats for subsections of the deck, and it's not time
critical code
- people who've been using anki since the very early days may notice a drop in
statistics, as early repetitions were recorded in the stats table but the
revlog didn't exist at that point.
- due bugs in old syncs and imports/exports, the stats and revlog may not
match numbers exactly
To remove it, the following changes have been made:
- the graphs and deck stats now generate their data entirely from the revlog
- there are no stats to keep track of how many cards we've answered, so we
pull that information from the revlog in reset()
- we remove _globalStats and _dailyStats from the deck
- we check if a day rollover has occurred using failedCutoff instead
- we remove the getStats() routine
- the ETA code is currently disabled
- timeboxing routines use repsToday instead of stats
- remove stats delete from export
- remove stats table and index in upgrade
- remove stats syncing and globalStats refresh pre-sync
- remove stats count check in fullSync check, which was redundant anyway
- update unit tests
Also:
- newCountToday -> newCount, to bring it in line with revCount&failedCount
which also reflect the currently due count
- newCount -> newAvail
- timeboxing routines renamed since the old names were confusingly similar to
refreshSession() which does something different
Todo:
- update newSeenToday & repsToday when answering a card
- reimplement eta
- media is no longer hashed, and instead stored in the db using its original
name
- when adding media, its checksum is calculated and used to look for
duplicates
- duplicate filenames will result in a number tacked on the file
- the size column is used to count card references to media. If media is
referenced in a fact but not the question or answer, the count will be zero.
- there is no guarantee media will be listed in the media db if it is unused
on the question & answer
- if rebuildMediaDir(delete=True), then entries with zero references are
deleted, along with any unused files in the media dir.
- rebuildMediaDir() will update the internal checksums, and set the checksum
to "" if a file can't be found
- rebuildMediaDir() is a lot less destructive now, and will leave alone
directories it finds in the media folder (but not look in them either)
- rebuildMediaDir() returns more information about the state of media now
- the online and mobile clients will need to to make sure that when
downloading media, entries with no checksum are non-fatal and should not
abort the download process.
- the ref count is updated every time the q/a is updated - so the db should be
up to date after every add/edit/import
- since we look for media on the q/a now, card templates like '<img
src="{{{field}}}">' will work now
- export original files as gone as it is not needed anymore
- move from per-model media URL to deckVar. downloadMissingMedia() uses this
now. Deck subscriptions will have to be updated to share media another way.
- pass deck in formatQA, as latex support is going to change
Previously we used getCard() to fetch a card at the time. This required a
number of indices to perform efficiently, and the indices were expensive in
terms of disk space and time required to keep them up to date. Instead we now
gather a bunch of cards at once.
- Drop checkDue()/isDue so writes are not necessary to the DB when checking
for due cards
- Due counts checked on deck load, and only updated once a day or at the end
of a session. This prevents cards from expiring during reviews, leading to
confusing undo behaviour and due counts that go up instead of down as you
review. The default will be to only expire cards once a day, which represents
a change from the way things were done previously.
- Set deck var defaults on deck load/create instead of upgrade, which should
fix upgrade issues
- The scheduling code can now have bits and pieces switched out, which should
make review early / cram etc easier to integrate
- Cards with priority <= 0 now have their type incremented by three, so we can
get access to schedulable cards with a single column.
- rebuildQueue() -> reset()
- refresh() -> refreshSession()
- Views and many of the indices on the cards table are now obsolete and will
be removed in the future. I won't remove them straight away, so as to not
break backward compatibility.
- Use bigger intervals between successive card templates, as the previous
intervals were too small to represent in doubles in some circumstances
Still to do:
- review early
- learn more
- failing mature cards where delay1 > delay0
