Currently when fetching state groups from the data store we make two
hits two the database: once for members and once for non-members (unless
request is filtered to one or the other). This adds needless load to the
datbase, so this PR refactors the lookup to make only a single database
hit.
Splits the state_group_cache in two.
One half contains normal state events; the other contains member events.
The idea is that the lazyloading common case of: "I want a subset of member events plus all of the other state" can be accomplished efficiently by splitting the cache into two, and asking for "all events" from the non-members cache, and "just these keys" from the members cache. This means we can avoid having to make DictionaryCache aware of these sort of complicated queries, whilst letting LL requests benefit from the caching.
Previously we were unable to sensibly use the caching and had to pull all state from the DB irrespective of the filtering, which made things slow. Hopefully fixes https://github.com/matrix-org/synapse/issues/3720.
This is the first tranche of support for room versioning. It includes:
* setting the default room version in the config file
* new room_version param on the createRoom API
* storing the version of newly-created rooms in the m.room.create event
* fishing the version of existing rooms out of the m.room.create event
When _get_state_for_groups is given a wildcard filter, just do a complete
lookup. Hopefully this will give us the best of both worlds by not filling up
the ram if we only need one or two keys, but also making the cache still work
for the federation reader usecase.
Fixes a regression that had crept in where the caching layer upholds requests for loading state which is filtered by type (but not by state_key), but the DB layer itself would interpret a missing state_key as a request to filter by null state_key rather than returning all state_keys.
Will Hunt