IndexedDB: Add initial types and database migrations for EventCacheStore backend

[mgoldenberg]

Background

This pull request is part of a series of pull requests to add an IndexedDB implementation of the EventCacheStore (see #4617, #4996, #5090). This particular pull request provides initial types and a database schema.

Changes

This change does not expose any code, but simply adds the initial types and migrations that will be used in the implementation of EventCacheStore. Ideally, the schema would mimic the one used in the SQLite implementation of EventCacheStore, but given that IndexedDB is not relational, the schema needed some modification.

Queries

The following queries are used in the implementation of EventCacheStore and so, must be supported in our schema.

1. RoomId → Next ChunkIdentifier
2. RoomId, ChunkIdentifier → All Events in corresponding Chunk
3. RoomId → Last Chunk in LinkedChunks
4. RoomId, EventId → Event
5. RoomId, EventId → Position, if any, in LinkedChunks
6. RoomId, EventId, RelationType → All Events related to EventId by RelationType

Schema

• CORE - Object store
  • No primary key, used for dealing with leases and other miscellaneous data
• LINKED_CHUNKS - Object store
  • Key - id - composed of RoomId and ChunkIdentifier
  • Value - object representing a Chunk
  • Supports queries (1), (2)
• LINKED_CHUNKS_NEXT - Index on LINKED_CHUNKS
  • Key - next - composed of RoomId and ChunkIdentifier
  • Value - same as LINKED_CHUNKS
  • Supports query (3)
• EVENTS - Object store
  • Key - id - composed of RoomId and EventId
  • Value - object representing an Event
  • Supports queries (4)
• EVENTS_POSITION - Index on EVENTS
  • Key - position - composed of RoomId and ChunkIdentifier
  • Value - same as EVENTS
  • Supports query (5)
• EVENTS_RELATION - Index on EVENTS
  • Key - relation - composed of RoomId, EventId, RelationType
  • Value - same as EVENTS
  • Supports query (6)

Types

There are two sets of types which will be used for performing various operations.

1. event_cache_store::types - decrypted, used for high-level operations on the data itself
2. event_cache_store::serializer::types - may be encrypted, used to store encoded data but exposes certain values for effective querying

These types will have implicit conversions from one to the other during (de)serialization, however, that is not included in this pull request.

Future Work

• Add conversions and (de)serialization functions for all types in event_cache_store::types
• Add implementation of EventCacheStore which uses these types

---

• Public API changes documented in changelogs (optional)

Signed-off-by: Michael Goldenberg [email protected]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.16%. Comparing base (f3f3d96) to head (922ea91).
Report is 12 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5138      +/-   ##
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+ Coverage   85.15%   85.16%   +0.01%     
==========================================
  Files         329      329              
  Lines       36923    36923              
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+ Hits        31442    31447       +5     
+ Misses       5481     5476       -5     

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[Hywan]

Pretty cool! I have a couple of tiny feedback. Other than that, it's good and easy to follow. Thanks! I'm enjoying the code structure.

[mgoldenberg]

By the way, I made one additional change aside from those you requested.

Basically, the change is that GenericEvent now allows us to enforce a type-level distinction between in-band and out-of-band events. This is accomplished by making GenericEvent::position a required field, as opposed to an Option, as an Option only enforces a value distinction.

pub struct GenericEvent<P> {
    ...,
    pub position: Option<P>, // => position: P
}

pub type InBandEvent = GenericEvent<Position>;
pub type OutOfBandEvent = GenericEvent<()>;

This is already the case in another branch where I have all my changes, but I must have made a mistake when copying the code over into this branch.

[Hywan]

A couple of feedback regarding the doc, and a more robust Version enum to replace u32. Other than that, we are good!

[mgoldenberg]

@Hywan, sorry about the last minute changes after re-requesting a review 😬 I am working on the implementation in a separate branch, and realized some of the types should change slightly.

At any rate, I figured I might be able to sneak those changes in before you review - hope that's okay!

[Hywan]

All good to me! Congrats and thank you very much. Can you rebase your history please? Or would you prefer we squash everything on our side?

[mgoldenberg]

I rebased - hopefully everything passes!