Drizzle queries appear to use writeLock for SELECT statements - need help understanding if this is expected

[wturon]

Hey folks!

I'm experiencing a pretty bad performance issues in my React Native app where all database queries seem to block each other (5-10 second freezes). I've traced the execution paths and it appears that there's a writeLock being set for all queries.

What I'm Observing

When I trace the execution paths of different query types, I'm seeing that all Drizzle queries route through executeRaw() -> writeLock(), while raw PowerSync queries use readLock():

Drizzle queries (all use writeLock):

• db.query.findMany() → executeRaw() → writeLock
• db.query.findFirst() → executeRaw() → writeLock
• db.select().from() → executeRaw() → writeLock
• db.select({ cols }).from() → executeRaw() → writeLock

Raw PowerSync queries (use readLock):

• powerSyncDb.getAll() → getAll() → readLock
• powerSyncDb.get() → get() → readLock

Environment

• @powersync/drizzle-driver: ^0.6.0
• @powersync/op-sqlite: ^0.7.11
• @powersync/react-native: ^1.25.1
• @powersync/common: ^1.40.0
• drizzle-orm: ^0.39.3
• Platform: React Native (Expo)
• SQLite: WAL mode enabled

Code Path I'm Seeing

Looking at the source, it appears the execution goes:

  PowerSyncSQLitePreparedQuery:
  async values(placeholderValues) {
      const params = fillPlaceholders(this.query.params, placeholderValues ?? {});
      this.logger.logQuery(this.query.sql, params);
      return await this.db.executeRaw(this.query.sql, params);
  }

This values() method is called by both .all() and .get() when field mappings exist (which seems to always be the case with Drizzle's query builder).

  Then in OPSqliteAdapter:
  executeRaw(query, params) {
      return this.writeLock(ctx => ctx.executeRaw(query, params));
  }

My Questions

1. Is this the expected behavior for executeRaw()? Should it use writeLock() even for SELECT queries?
2. Is there a different code path I should be using for read queries with Drizzle?
3. Should .values() be calling a different method for SELECT queries?

I have test code that traces the exact execution paths if that would be helpful!

Thanks so much for any guidance! Really appreciate all the work you've done on PowerSync - it's been great otherwise. 🙏