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Support URIs on ATTACH #373
Description
Hello!
After changing the stack to the latest versions based on sqlite3 v3 (powersync + sqlite_async), we've noticed that some of our read only ATTACHed databases could cause locking issues to the writer isolate if we don't properly ATTACH them with the read only flag ?mode=ro.
https://sqlite.org/uri.html
We still need to isolate to issue to a reproducible case, so I'll update once I have more info, but what we found is that if we mark the database that we attach to as read only with ?mode=ro, it resolves the locking issues. We are using WAL in the main database and sqlite3mc if that matters.
What I would propose is to change the default compilation flags and set SQLITE_USE_URI=1 so that the URI syntax is supported when ATTACHing.
Another option would be using the runtime configuration with sqlite3_config(SQLITE_CONFIG_URI, 1), which is not currently in the bindings. I've tried to expose it, but I wasn't able to make it work correctly, as it needs to be called before sqlite3_initialize, per the sqlite3_config function docs.
Activity
simolus3 commentedon May 18, 2026
I believe we only call
sqlite3_initializewhen a database connection is opened. So if you overrideNativeIsolateOpenFactory.openNativeConnectionto callsqlite3_config, that should work.But I also see that it's very difficult to do that correctly at the moment. If you use
@Nativeexternals to definesqlite3_config, you'd have to add a@DefaultAsset('package:sqlite3/src/ffi/libsqlite3.g.dart')annotation to the enclosing Dart file to make sure you use the same SQLite library as thesqlite3package.I could add
sqlite3_configtopackage:sqlite3/unstable/ffi_bindings.dartif that helps, or expose typed configuration options (like we do forsqlite3_db_config).I'm kind of worried about this potentially being a breaking change, e.g. if someone manages to use file names that would be valid URIs.
davidmartos96 commentedon May 18, 2026
@simolus3 I was getting MISUSE errors when I added the sqlite3_config function and used it from the multi isolate project with powersync. Maybe I did something wrong in the implementation.