feature: Add function to set journal mode on sqlite databases #443
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| public extension SQLiteDatabase { | ||
| func setJournalMode<T>(mode: T) throws where T : RawRepresentable, T.RawValue == String { } |
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This extension ensures it's not a breaking change for projects that have written their own SQLiteDatabase implementation.
| public enum JournalMode: String { | ||
| /// The rollback journal is deleted at the conclusion of each transaction. This is the default behaviour. | ||
| case delete = "DELETE" | ||
| /// Commits transactions by truncating the rollback journal to zero-length instead of deleting it. | ||
| case truncate = "TRUNCATE" | ||
| /// Prevents the rollback journal from being deleted at the end of each transaction. Instead, the header | ||
| /// of the journal is overwritten with zeros. | ||
| case persist = "PERSIST" | ||
| /// Stores the rollback journal in volatile RAM. This saves disk I/O but at the expense of database | ||
| /// safety and integrity. | ||
| case memory = "MEMORY" | ||
| /// Uses a write-ahead log instead of a rollback journal to implement transactions. The WAL journaling | ||
| /// mode is persistent; after being set it stays in effect across multiple database connections and after | ||
| /// closing and reopening the database. | ||
| case wal = "WAL" | ||
| /// Disables the rollback journal completely | ||
| case off = "OFF" | ||
| } |
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Is it possible some other SQLite implementation would have different journal modes? Are these modes intrinsic to SQLite or just to the SQLite.swift implementation?
If the are universally the journal modes of SQLite, then I don't think this should be part of our specific implementation. The setJournalMode function in the protocol could just take in this enum instead of being generic.
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I suppose there might be but these come directly from sqlite.org documentation so if there is an sqlite implementation that differs enough you'll probably want to write your own SQLiteDatabase implementation too at which point you get to define the new set of journal modes.
As for the generic parameter I simply wanted something that was able to be expressible as a String since that's how the pragma statement gets built. Moving the enum into SQLiteDatabase will serve the vast majority of users although I didn't like how protocols can't hold enums so we lost some namespacing there.
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Refactored as we discussed in 27cc399.
70c34472 feature: Add function to set journal mode on sqlite databases (#443) 5f529536 Update ROADMAP.md git-subtree-dir: apollo-ios git-subtree-split: 70c3447284b9fdeba7bbc2292644c494243ad0fb
…de on sqlite databases git-subtree-dir: apollo-ios git-subtree-mainline: 90cabb5 git-subtree-split: 70c3447284b9fdeba7bbc2292644c494243ad0fb
Closes apollographql/apollo-ios#3399.
There are many other
PRAGMAcommands that sqlite supports so there were a few ways this could have been implemented:executeorrunfunctions public onSQLiteDatabasebut this is potentially the most destructive as it's a wide open door to executing anything against the connected database.setPragmafunction that would execute thePRAGMA <statement>command. This narrows the scope to onlyPRAGMAstatements but this is also potentially destructive as I am not familiar with all the pragma statements and their effects.setJournalModefunction that only allows the journal mode to be set. This is very narrow in scope but the safest since it solves the requested feature and it's a single statement to grok.I chose option 3, so this PR adds a protocol function to allow sqlite database implementations to set the journal mode of the connected database.
JournalModepragma values were taken from https://www.sqlite.org/pragma.html#pragma_journal_mode.