Swift Driver Additions #262
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# Conflicts: # CHANGELOG.md # core/src/commonMain/kotlin/com/powersync/PowerSyncDatabase.kt # core/src/commonMain/kotlin/com/powersync/PowerSyncDatabaseFactory.kt # core/src/nativeMain/kotlin/com/powersync/sqlite/Database.kt # gradle/libs.versions.toml
simolus3
reviewed
Sep 17, 2025
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| fun loadExtension( | ||
| public fun loadExtension( |
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If the intention is to call this method from Swift, should it have a @Throws annotation?
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| @OptIn(ExperimentalPowerSyncAPI::class) | ||
| public open class SwiftSQLiteConnectionPool |
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Since it looks like we wouldn't extend this class from Swift, I don't think it would have to be open?
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Overview
This adds additional helpers to the
PowerSyncKotlinmodule for implementing custom SQLite Drivers in the Swift SDK.Related to powersync-ja/powersync-swift#78
The main addition in this PR is a
SwiftSQLiteConnectionPoolimplementation which can be used to bridge a Swift connection pool to the format expected by our Kotlin SDK.Connection Pooling
For GRDB in particular: we can create a GRDB
DatabasePoolwhich can be mapped to a KotlinSQLiteConnectionPool. GRDB provides a pointer to the raw SQLite connection when obtaining a lease to a pooled connection. We can use this pointer on the Kotlin side with the existingDatabaseconnection implementation.GRDB only allows synchronous closures to access connection leases. The closure is executed in a managed dispatch queue. The
SwiftSQLiteConnectionPoolruns the Kotlin suspending callbacks in this synchronous environment by using arunBlockingcall. This should be fine since we are only blocking the thread provided by the dispatch queue.Table Updates
The Kotlin
SQLiteConnectionPoolrequires aSharedFlowof Strings representing the tables changed. GRDB provides it's own update hooks which we can use to feed this flow. We can't generate a KotlinFlow easily on the Swift side - theSwiftSQLiteConnectionPoolgenerates a mutable flow internally and exposes a public method to update to update this flow. The GRDB hooks trigger this method in order to convey updates.tryEmitand backpressureStatic SQLite
GRDB relies on the system SQLite implementation by default. For our purposes, we require a custom compiled version which supports extension loading. The Kotlin SDK already compiles a static version of SQLite which we include in the Swift SDK. Including our PowerSync Swift SDK in a build currently overrides the SQLite implementation used by GRDB - providing support for extension loading. GRDB has some of its own requirements for SQLite. For its version of watched/observed queries it makes calls to
sqlite3_snapshot_get. This API is only available if the SQLITE_ENABLE_SNAPSHOT compile setting is enabled. This compiler flag is now enabled in our build for compatibility.