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Some incomplete notes about AnkiApp's internals.

Note: The add-on no longer imports from the SQLite database as of version 3.0.0

Terminology

AnkiApp's uses familiar terms like decks, cards, and tags, with some differences:

  • knol: a "knol" can be thought of as the counterpart of a note in Anki.1
  • layout: a layout is like a notetype with a single card type in Anki.

Tables

The database has the following tables:

knol_values

This table contains the contents of each note field in the following format:

id knol_id knol_key_name value
7df6b7685e0a44bcbbf562637efe1c96 001c3c5b71f945e29c45368c0237cb08 Front What is the capital of Ukraine?
a82b69c4abd14b92b6ad12c3743bde76 001c3c5b71f945e29c45368c0237cb08 Back Kyiv
79606c0a79324d9c841a7c92a3784481 0012a6ae0a0847838937fcbd18ea16d1 Word ebb
7b0b88f4398c417ebe22c7a1c49e3ada 0012a6ae0a0847838937fcbd18ea16d1 Translation جزر
e0283190c4444d1b9f71933b0157fbaf 0012a6ae0a0847838937fcbd18ea16d1 Extra See "ebb and flow"

As you can guess, knol_key_name is the field name and value contains the field contents. Rows that have the same knol_id value belongs to the same note.

knol_keys

This table containts (apparently) redundant data about the names of fields that can be obtained from knol_values too. It's ignored by the add-on.

name
Front
Back
Extra

knols

This table just contains the IDs of knols:

id
001c3c5b71f945e29c45368c0237cb08
0012a6ae0a0847838937fcbd18ea16d1

Again, this seems redundant with the existence of the knol_values table.

knol_blobs

This table stores media files:

id knol_value_id type value
1d8359fe48c04bebbbc52e2b0f7ed4d1 d8e840834f1d4c12aa0b99d56013693e image/gif R0lGODlhk...
46872580a15d4fdda1931bd54f2d08af 0d783dc044024ee1adfafd707c1af9e2 image/jpeg /9j/4AAQSk...
708c2c0cac1641df881ed6ba8a2f1e0c 7a8b667a277c4bf8b55e81cc5c88c4dd image/webp UklGR...
  • knol_value_id: the ID of the knol_values row where the media file is used (which implies that there can be duplicate files with the exact same contents used in different fields or notes.)
  • type: the MIME type of the file.
  • value: the Base64-encoded contents of the file.

The IDs of media files are referenced in fields (knol_values->value columns) like this:

{{blob 1d8359fe48c04bebbbc52e2b0f7ed4d1}}

NOTE: It appears that with recent AnkiApp versions (6.1.0), media files are no longer stored in the knol_blobs table. Instead, they are stored as normal files separetely from the database file.

layouts

The layouts table has the following format:

id name templates style response_type_id status
acf3bd5e3fc94d64a9b21d7a531a6563 Front-to-Back ["<div>{{Front}}</div>","<div>{{front}}</div><hr/><div>{{Back}}</div>"] div { font-size: x-large; } 5b4f816026f511e2aac3001e52fffe46 0
a4abf3245c0340c39e43216fcd714dfc Translation ["<div>{{Word}}</div>","<div>{{Translation}}</div>"] div { font-size: x-large; } 5b4f816026f511e2aac3001e52fffe46 0
  • templates: the front and back templates stored as a string representation of a Python list (apparently).
  • style: CSS styles
  • response_type_id: TODO
  • status: TODO

knol_keys_layouts

This table maps each field to its layout:

layout_id knol_key_name
8fe1b4d10fbf403f875b53645bb0bd7e Front
8fe1b4d10fbf403f875b53645bb0bd7e Back
a4abf3245c0340c39e43216fcd714dfc Word
a4abf3245c0340c39e43216fcd714dfc Translation
a4abf3245c0340c39e43216fcd714dfc Extra

knols_tags

This contains the tags of each note.

knol_id tag_name
001c3c5b71f945e29c45368c0237cb08 Geography
0012a6ae0a0847838937fcbd18ea16d1 English

decks

The decks table has the following format:

id status name description created_at modified_at layout_id
a4dde94984644cf3a749a1898e47261c 1 Geography Trivia 2020-06-28T21:17:30.239Z 2020-06-28T21:17:30.239Z 8fe1b4d10fbf403f875b53645bb0bd7e
3662fdc90bfe4a86b11499101b298ecd 1 English English Vocabulary 2020-07-13T17:14:10.219Z 2020-07-13T17:14:10.219Z a4abf3245c0340c39e43216fcd714dfc
  • status: TODO
  • created_at and modified_at are UTC times in the ISO 8601 format.
  • layout_id: AnkiApp associates each deck with a single layout, so moving cards from one deck to another with a different layout can cause problems.

cards

Cards are stored in the following format:

id knol_id layout_id created_at modified_at score_mean score_standard_deviation last_response_at num_responses
1ea545da042dd9155bb04272ab7b7f45 001c3c5b71f945e29c45368c0237cb08 acf3bd5e3fc94d64a9b21d7a531a6563 1646433031244 1646433031244 0.761578857898712 0.0322830599592049 2021-06-03T20:12:03.105Z 5
a0f508207855d53210bccff65c0bfdfb 0012a6ae0a0847838937fcbd18ea16d1 a4abf3245c0340c39e43216fcd714dfc 1646433031245 1646433031245 NULL NULL NULL 0

Most of the columns should be self-explanatory at this point, except:

  • score_mean: TODO
  • score_standard_deviation: TODO
  • last_response_at: date of last review.
  • num_responses: number of reviews of this card.

cards_decks

This table tells us in which deck is each card:

card_id deck_id
1ea545da042dd9155bb04272ab7b7f45 a4dde94984644cf3a749a1898e47261c
a0f508207855d53210bccff65c0bfdfb 3662fdc90bfe4a86b11499101b298ecd

decks_knols

This table apparently associates knols with decks like it's done for cards for some reason:

knol_id deck_id
001c3c5b71f945e29c45368c0237cb08 a4dde94984644cf3a749a1898e47261c
0012a6ae0a0847838937fcbd18ea16d1 3662fdc90bfe4a86b11499101b298ecd

TODO: understand what is the purpose of this.

decks_layouts

We said earlier that AnkiApp associates each deck with a single layout as implied by the existence of the layout_id column in the decks table. But here, with data taken from the wild, we see that a deck can be associated with multiple layouts (!):

deck_id layout_id
a4dde94984644cf3a749a1898e47261c 8fe1b4d10fbf403f875b53645bb0bd7e
a4dde94984644cf3a749a1898e47261c a4abf3245c0340c39e43216fcd714dfc
a4dde94984644cf3a749a1898e47261c acf3bd5e3fc94d64a9b21d7a531a6563
3662fdc90bfe4a86b11499101b298ecd a4abf3245c0340c39e43216fcd714dfc

I have no idea how AnkiApp uses this table. It's not used by the add-on since in Anki decks and notetypes are not tied together in any way.

decks_tags

Apparently decks can have tags too. This table stores each deck's tags:

deck_id tag_name
a4dde94984644cf3a749a1898e47261c geography
a4dde94984644cf3a749a1898e47261c capitals
3662fdc90bfe4a86b11499101b298ecd english
3662fdc90bfe4a86b11499101b298ecd language

operations

TODO

id device_id timestamp type created_at object_type object_parameters

response_types

TODO:

id name
5b4f816026f511e2aac3001e52fffe46 basic

responses

This stores data similar to the scheduling information stored in the cards table, along with some additional info:

device_id knol_id deck_id layout_id duration_ms created_at score score_mean score_standard_deviation last_response_at
fdeb4ecfea1a4259ba2879aad0645642 0012a6ae0a0847838937fcbd18ea16d1 3afcf396cad54ddd83cbbce87ec72fb0 acf3bd5e3fc94d64a9b21d7a531a6563 7248 2021-12-03T07:33:34.973Z 0.75 0.830052375793457 0.0957268849015236 2021-07-13T17:16:13Z
fdeb4ecfea1a4259ba2879aad0645642 0012a6ae0a0847838937fcbd18ea16d1 3afcf396cad54ddd83cbbce87ec72fb0 acf3bd5e3fc94d64a9b21d7a531a6563 3530 2021-12-03T07:34:03.144Z 0.769999980926514 0.790026187896729 0.0786378681659699 2021-12-03T07:33:34Z

TODO: explain.

subscriptions

TODO: this is apparently has something to do with shared decks?

deck_id modified_at deck_name deck_description user_id
a4dde94984644cf3a749a1898e47261c 2020-06-28T21:17:30.239Z Geography deadbeefdeadbeefdeadbeefdeadbeef
3662fdc90bfe4a86b11499101b298ecd 2020-07-13T17:14:10.219Z English deadbeefdeadbeefdeadbeefdeadbeef

Security

Media

AnkiApp leaves users' media files exposed on its servers. Given a blob ID like 2e0957ca348e4e6ab480871628e59622, the media file can be downloaded by simply accessing the URL https://blobs.ankiapp.com/2e0957ca348e4e6ab480871628e59622.

More context: https://forums.ankiweb.net/t/ankiapp-importer/16734/52

API

Notes about the AnkiApp's API accessible from https://api.ankiapp.com

TODO: investigate using the API as an alternative method for importing.

Cards data

Knol values are fetched by initiating a request like this:

https://api.ankiapp.com/decks/{deck_id}/knols/{knol_id}?client_version={ankiapp_version}&client_id={client_id}&t={token}

Footnotes

  1. "knol" is probably a reference to Knol. ↩