You have changed the code snippets in your link.

The original link highlighted this snippet:

  Future<void> insertEmbedding(EmbeddingProto embedding) async {
      final db = await _database;
      await db.writeTransaction((tx) async {
        await tx.execute('INSERT INTO $tableName ($columnEmbedding) values(?)',
            [embedding.writeToBuffer()]);
      });
  }

Now highlighted:

  Future<void> insertMultipleEmbeddings(List<EmbeddingProto> embeddings) async {
    final db = await _database;
    final inputs = embeddings.map((e) => [e.writeToBuffer()]).toList();
    await db.executeBatch(
        'INSERT INTO $tableName ($columnEmbedding) values(?)', inputs);
  }

Did you post the wrong link the first time and corrected your mistake? Or did you change the snippet because @electroly was right about the code being inefficient?