[Mega-Issue] Cache Improvements

[designatednerd]

This Mega-Issue helps summarize and link to all the various things we're working on around improvements to the cache for high-level planning purposes. This issue will be updated as things change. Please open any comments on more specific issues, or file a new issue. Thank you!

Note: New issues will likely be added as we finish up our new codegen, since changes may be needed to make that work.

New features we're definitely doing

• Add cache eviction / expiration #142 Cache eviction and expiration
• [issue TBA] Better handling of paginated data
• Field-level metadata for the cache #1568 Add field-level metadata to facilitate expiration
• Figure out how to test cache key generation with JSON objects #1304 Better testing for generating keys from dynamic objects

Bugs we want to fix

• Cannot return data from the SQLite cache if the query has "." #1071 Cache key separator shouldn't be . because it interferes with properties with a period in them (such as filenames)
• GraphQLQueryWatcher retained by ApolloStore #516, crash if ApolloClient released before GraphQLQueryWatcher #678 GraphQLWatcher retain cycle handling
• Watch does not call callback on cold cache start #99 Better handling of callbacks when first starting a watcher
• Enormous amounts of data make GraphQLDependencyTracker use huge amounts of memory #1683 huge amounts of memory used when parsing huge queries into the cache

New features we hope to do, but maybe not immediately

• Feature Request: option to provide restoration objects for optimistic caching #1196 Optimistic Caching & rollbacks
• Add refetchQueries to mutations #884 add option to refetch queries after a mutation
• Feature Request: Fetch More for caching #565 fetch more for paginated requests

New features we would like to do, but not right now

• Granularity in error handling #197 Propagating errors to the field which caused them
• [Issue TBA] Ability to chain different caches (ex, In-memory as primary, SQLite as fallback)