How to run 'rw' transaction in parallel with 'r' transaction?

[bishoyroufael]

I have a scenario where I am inserting data that is big in chunks to dexie tables. This process might take a while. At the same time, I want the user to be able to do things like searching in such tables even if the insertion process isn't done yet. Is that kind of concurrency supported with dexie or not?

export async function insert_data(
  data: Array<Data>,
  chunkSize: number = 200,
  onProgress: (progress: { total: number; completed: number }) => void
): Promise<void> {
  const totalItems = data.length;
  let completedItems = 0;

  try {
    // Helper function to process chunks and update progress
    const processChunks = async <T>(data: T[], store: EntityTable<any, any>, label: string) => {
      for (const chunk of chunkArray(data, chunkSize)) {
        await store.bulkPut(chunk);
        completedItems += chunk.length;
        onProgress({ total: totalItems, completed: completedItems });
      }
    };

    // Start transaction for insertion
    await db.transaction('rw', db.Data, async () => {
      await processChunks(data, db.Data, 'data');
    });
    
    } catch (e) {
    console.error("Error during bulk insertion:", e);
    onProgress({ total: totalItems, completed: completedItems }); // Report progress in case of error
  }
}

// Is it possible to run another transaction in parallel to read from db.Data table?

[dfahlander]

Hi! No, indexedDB will lock the table ("Data" in this case) from both read and write during an 'rw' transaction but other tables can be read in paralell. If each chunk is added in its own transaction (which will implicitly be the case if you just do bulkPut() without a transaction) it would leave some air for read queries to be done in between.

However, in my opinion, the user experience would probably be the best if applications goes into a specific state, showing some kind of spinner or progress and nothing else during heavy sync operations. In such a state, best performance is gained if all components using liveQuery is unmounted so the user only sees the progress message and nothing else until sync is done.