TODO.md

Cleanup

• SQLCipher: sqlite3_rekey is discouraged (ccgus/fmdb#547 (comment))
• Write regression tests for #156 and #157
• Fix matchingRowIds (todo: what is the problem, already?)
• deprecate ScopeAdapter(base, scopes), because base.addingScopes has a better implementation
• groue/GRDB.swift#514
• Test NOT TESTED methods
• Cancellation of a started ValueObservation. Context: groue/GRDB.swift#601 (comment)
• Remove submodules

Documentation

• Document that creating "too many" ValueObservation increases database contention. This also applies to database pools, because when observations create reader contention, they also create writer contention. Context: groue/GRDB.swift#601 (comment)
• Enhance the introduction to SQLRequest, based on the feedback in groue/GRDB.swift#617
• Association: document how to use aggregates with inner join (testAnnotatedWithHasManyDefaultMaxJoiningRequired)
• Association: document ordered vs. non-ordered hasMany and hasManyThrough associations

Features

• request.exists(db) as an alternative to fetchOne(db) != nil. Can generate optimized SQL.
• Measure the duration of transactions
• Improve SQL generation for Player.....fetchCount(db), especially with distinct. Try to avoid SELECT COUNT(*) FROM (SELECT DISTINCT player.* ...)
• Alternative technique for custom SQLite builds: see the Podfile at CocoaPods/CocoaPods#9104, and https://github.com/clemensg/sqlite3pod
• Attach databases. Interesting question: what happens when one attaches a non-WAL db to a databasePool?
• SQL Generation
  • date functions
  • NOW/CURRENT_TIMESTAMP
  • ROUND() http://marc.info/?l=sqlite-users&m=130419182719263
  • RANDOM() https://www.sqlite.org/lang_corefunc.html
  • GLOB https://www.sqlite.org/lang_expr.html
  • REGEXP https://www.sqlite.org/lang_expr.html
  • CASE x WHEN w1 THEN r1 WHEN w2 THEN r2 ELSE r3 END https://www.sqlite.org/lang_expr.html
• Allow concurrent reads from a snapshot
• Decode NSDecimalNumber from text database values
• Check https://sqlite.org/sqlar.html
• FTS: prefix queries
• A way to stop a ValueObservation observer without waiting for deinit
• More schema alterations
• DatabasePool.databaseSchemaIsLocked = true (should forbid schema changes, and never reset dbPool readers' caches). Or can we invalidate reader's cache automatically from the writer connection?
• Database.clearSchemaCache() is fine, but what about dbPool readers? Can we invalidate the cache for a whole pool?

Unsure if necessary

• Remove support for suspended databases - https://inessential.com/2020/02/13/how_we_fixed_the_dreaded_0xdead10cc_cras
• https://sqlite.org/pragma.html#pragma_index_xinfo
• Deprecate DatabaseQueue/Pool.addFunction, collation, tokenizer: those should be done in Configuration.prepareDatabase
• filter(rowid:), filter(rowids:)
• https://github.com/apple/swift-evolution/blob/master/proposals/0075-import-test.md
• https://forums.swift.org/t/how-to-encode-objects-of-unknown-type/12253/6
• Configuration.crashOnError = true
• Glossary (Database Access Methods, etc.)
• ValueObservation.flatMap. Not sure it is still useful now that we have ValueObservation.tracking(value:)
• rename fetchOne to fetchFirst. Not sure because it is a big breaking change. Not sure because ValueObservation.tracking(value:) has reduced the need for observationForFirst.
• Not sure: type safety for SQL expressions
  • Introduce some record protocol with an associated primary key type. Restrict filter(key:) methods to this type. Allow distinguishing FooId from BarId types.
  • Replace Column with TypedColumn. How to avoid code duplication (repeated types)? Keypaths?
• Cursor.underestimatedCount, which could speed up Array(cursor) and fetchAll()
• Remove prefix from association keys when association name is namespaced: groue/GRDB.swift#584 (comment)
• Alternative support for custom SQLite builds, wih CocoaPods: CocoaPods/CocoaPods#9103
• Introduce a ValueObservation "mode" which lifts the guarantee that all changes are notified, but allows it to perform its initial fetch immediately when supported by a DatabasePool. Context: groue/GRDB.swift#601 (comment)

Unsure how

• Association limits: Author.including(optional: Author.books.order(date.desc).first)

• Joins and full-text tables

• UPSERT https://www.sqlite.org/lang_UPSERT.html

• Support for "INSERT INTO ... SELECT ...".

• Look at the jazzy configuration of https://github.com/bignerdranch/Deferred

• Predicates, so that a filter can be evaluated both on the database, and on a record instance.

  After investigation, we can't do it reliably without knowing the collation used by a column. And SQLite does not provide this information elsewhere than in the full CREATE TABLE statement stored in sqlite_master.

• ValueObservation erasure

  // Do better than this
  observation.mapReducer { _, reducer in AnyValueReducer(reducer) }
  

• new.updateChanges(from: old) vs. old.updateChanges(with: { old.a = new.a }). This is confusing.

Reading list

• Documentation generation: https://twitter.com/jckarter/status/987525569196650496: cmark is the implementation the Swift compiler uses for doc comments etc.
• VACUUM (https://blogs.gnome.org/jnelson/)
• http://www.sqlite.org/intern-v-extern-blob.html
• https://sqlite.org/sharedcache.html
• Undo: https://www.sqlite.org/undoredo.html
• Undo: https://sqlite.org/sessionintro.html
• Swift, Xcode:List of Swift documentation keywords: https://swift.org/documentation/api-design-guidelines.html#special-instructions
• Swift, Xcode:Amazing tip from Xcode labs: add a EXCLUDED_SOURCE_FILE_NAMES build setting to conditionally exclude sources for different configuration: https://twitter.com/zats/status/74386298602026496
• SQLITE_ENABLE_SQLLOG: http://mjtsai.com/blog/2016/07/19/sqlite_enable_sqllog/
• Swift, Xcode: https://github.com/apple/swift/blob/master/docs/OptimizationTips.rst
• Associations: http://docs.diesel.rs/diesel/associations/index.html
• FTS: http://cocoamine.net/blog/2015/09/07/contentless-fts4-for-large-immutable-documents/
• pinyin: http://hustlzp.com/post/2016/02/ios-full-text-search-using-sqlite-fts4
• Realm oddity: http://stackoverflow.com/questions/41721769/realm-update-object-without-updating-lists
• File protection: ccgus/fmdb#262
• File protection: https://lists.apple.com/archives/cocoa-dev/2012/Aug/msg00527.html
• iOS apps are terminated every time they enter the background if they share an encrypted database with an app extension
• Cross-Process notifications with CFNotificationCenterGetDarwinNotifyCenter