在cassandra中保留一个zip文件并将其读回

Question

I need to persist a zip file in cassandra data base. And I need to get it back in another program. For persisting it, I am using the following code-

    bin_data = open("Model-File.zip", 'rb').read()
    bin_data=bin_data.decode('latin-1').encode("utf-8")

This bin_data I can persist to cassandra in string format-

    CQLString = "INSERT INTO testkeyspacenew.model (modelid, data) 
    VALUES(%s,%s)"
    session.execute(CQLString, (model_id,bin_data))

However when reading it back, I am unable to get the bin_data in the format in which it was in the beginning. Hence unable to recreate the zip file. Please help. This is what I tried during reading-

    abc=session.execute(CQLString)
    for row in abc:
        data=row
    data=str(data)
    print (data.encode("utf-8").encode('latin-1'))

The data I am printing while reading is not same as the bin_data I got from the zip file.

Answer 1

Cassandra and CQL know a blob type which is probably what you want. See: https://docs.datastax.com/en/archived/cassandra/1.2/cassandra/tools/use_about_data_types_c.html

You are transcoding the binary data with bin_data=bin_data.decode('latin-1').encode("utf-8") which should not be necessary at all.

On top print (data.encode("utf-8").encode('latin-1')) shows two encode calls.

Edit: found a test from the DataStax driver using blob here https://github.com/datastax/python-driver/blob/master/tests/integration/standard/test_types.py

        s.execute("CREATE TABLE blobbytes2 (a ascii PRIMARY KEY, b blob)")

        params = ['key1', bytearray(b'blob1')]
        s.execute("INSERT INTO blobbytes2 (a, b) VALUES (%s, %s)", params)