How can I create a custom sqlite function in Android?

[danicomas]

I want to add a function (distance between two points) and I have seen in iOS is more easy. However, in Android I should recompile some c++ connector with ndk. Is this the way? Can someone explain me the correct steps to do my goal? @brodybits @marcucio

[brody4hire]

You would have to rebuild the Android-sqlite-native-driver. To rebuild the Android-sqlite-native-driver you have to follow the instructions very carefully.

[danicomas]

https://android.googlesource.com/platform/frameworks/base/+/refs/heads/master/core/java/android/database/sqlite/SQLiteCustomFunction.java uses is discarded for the >= SDK API 17 (4.2) support @brodybits? I think that using this it would be similar as iOS.

[brody4hire]

In that case you would use androidDatabaseImplementation: 2 when you open the database, and you would modify src/android/io/sqlc/SQLiteAndroidDatabase.java to use your custom function.

[danicomas]

And what do you think about the performance @brodybits? Exist more issues than the classic way?

I have seen this known issue in README.md for example:

INSERT statement that affects multiple rows (due to SELECT cause or using TRIGGER(s), for example) does not report proper rowsAffected on Android in case the built-in Android database used (using the androidDatabaseImplementation option in window.sqlitePlugin.openDatabase)

[brody4hire]

I think the performance would be better if you rebuild Android-sqlite-native-driver which is built using the Android NDK, but as I said you would have to follow the directions very carefully. The Android-sqlite-native-driver solution was designed to be general-purpose, and it does satisfy the needs of this plugin. I have not done much benchmarking so I cannot draw any definite conclusions.

The easier solution is to use androidDatabaseImplementation: 2 when you open the database and modify src/android/io/sqlc/SQLiteAndroidDatabase.java to use your custom function. This solution would suffer from the known issue if you use an INSERT statement that affects multiple rows. I did not see this issue affect too many users though.

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