New/rev card mixing, collapse time and the timeboxing limit are now a
collection property. I appreciate how it could be useful to have those
settings per top-level deck in some cases, but having some settings inherited
from the top level deck makes for a confusing UI.
Instead of having required and unique flags for every field, enforce both
requirements on the first field, and neither on the rest. This mirrors the
subject/body format people are used to in note-taking apps. The subject
defines the object being learnt, and the remaining fields represent properties
of that object.
In the past, duplicate checking served two purposes: it quickly notified the
user that they're entering the same fact twice, and it notified the user if
they'd accidentally mistyped a secondary field. The former behaviour is
important for avoiding wasted effort, and so it should be done in real time.
The latter behaviour is not essential however - a typo is not wasted effort,
and it could be fixed in a periodic 'find duplicates' function. Given that
some users ended up with sluggish decks due to the overhead a large number of
facts * a large number of unique fields caused, this seems like a change for
the better.
This also means Anki will let you add notes as long as as the first field has
been filled out. Again, this is not a big deal: Anki is still checking to make
sure one or more cards will be generated, and the user can easily add any
missing fields later.
As a bonus, this change simplifies field configuration somewhat. As the card
layout and field dialogs are a popular point of confusion, the more they can
be simplified, the better.
The full sync threshold was a hack to ensure we synced the deck in a
memory-efficient way if there was a lot of data to send. The problem is that
it's not easy for the user to predict how many changes there are, and so it
might come as a surprise to them when a sync suddenly switches to a full sync.
In order to be able to send changes in chunks rather than all at once, some
changes had to be made:
- Clients now set usn=-1 when they modify an object, which allows us to
distinguish between objects that have been modified on the server, and ones
that have been modified on the client. If we don't do this, we would have to
buffer the local changes in a temporary location before adding the server
changes.
- Before a client sends the objects to the server, it changes the usn to
maxUsn both in the payload and the local storage.
- We do deletions at the start
- To determine which card or fact is newer, we have to fetch the modification
time of the local version. We do this in batches rather than try to load the
entire list in memory.
Decks now have an "update sequence number". All objects also have a USN, which
is set to the deck USN each time they are modified. When syncing, each side
sends any objects with a USN >= clientUSN. When objects are copied via sync,
they have their USNs bumped to the current serverUSN. After a sync, the USN on
both sides is set to serverUSN + 1.
This solves the failing three way test, ensures we receive all changes
regardless of clock drift, and as the revlog also has a USN now, ensures that
old revlog entries are imported properly too.
Objects retain a separate modification time, which is used for conflict
resolution, deck subscriptions/importing, and info for the user.
Note that if the clock is too far off, it will still cause confusion for
users, as the due counts may be different depending on the time. For this
reason it's probably a good idea to keep a limit on how far the clock can
deviate.
We still keep track of the last sync time, but only so we can determine if the
schema has changed since the last sync.
The media code needs to be updated to use USNs too.
While thinking about media syncing I realized the current sync algorithm is
flawed in certain cases. It might be time to think about using a USN instead,
as that should also hopefully solve the skewed clock problem properly.
Ported the sync code to the latest libanki structure. Key points:
No summary:
The old style got each side to fetch ids+mod times and required the client to
diff them and then request or bundle up the appropriate objects. Instead, we now
get each side to send all changed objects, and it's the responsibility of the
other side to decide what needs to be merged and what needs to be discarded.
This allows us to skip a separate summary step, which saves scanning tables
twice, and allows us to reduce server requests from 4 to 3.
Schema changes:
Certain operations that are difficult to merge (such as changing the number of
fields in a model, or deleting models or groups) result in a full sync. The
user is warned about it in the GUI before such schema-changing operations
execute.
Sync size:
For now, we don't try to deal with large incremental syncs. Because the cards,
facts and revlog can be large in memory (hundreds of megabytes in some cases),
they would have to be chunked for the benefit of devices with a low amount of
memory.
Currently findChanges() uses the full fact/card objects which we're planning to
send to the server. It could be rewritten to fetch a summary (just the id, mod
& rep columns) which would save some memory, and then compare against blocks
of a few hundred remote objects at a time. However, it's a bit more
complicated than that:
- If the local summary is huge it could exceed memory limits. Without a local
summary we'd have to query the db for each record, which could be a lot
slower.
- We currently accumulate a list of remote records we need to add locally.
This list also has the potential to get too big. We would need to
periodically commit the changes as we accumulate them.
- Merging a large amount of changes is also potentially slow on mobile
devices.
Given the fact that certain schema-changing operations require a full sync
anyway, I think it's probably best to concentrate on a chunked full sync for
now instead, as provided the user syncs periodically it should not be easy to
hit the full sync limits except after bulk editing operations.
Chunked partial syncing should be possible to add in the future without any
changes to the deck format.
Still to do:
- deck conf merging
- full syncing
- new http proxy
Like the previous change, models have been moved from a separate DB table to
an entry in the deck. We need them for many operations including reviewing,
and it's easier to keep them in memory than half on disk with a cache that
gets cleared every time we .reset(). This means they are easily serialized as
well - previously they were part Python and part JSON, which made access
confusing.
Because the data is all pulled from JSON now, the instance methods have been
moved to the model registry. Eg:
model.addField(...) -> deck.models.addField(model, ...).
- IDs are now timestamped as with groups et al.
- The data field for plugins was also removed. Config info can be added to
deck.conf; larger data should be stored externally.
- Upgrading needs to be updated for the new model structure.
- HexifyID() now accepts strings as well, as our IDs get converted to strings
in the serialization process.
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
