Can I pickle a python dictionary into a sqlite3 text field?

Question

Any gotchas I should be aware of? Can I store it in a text field, or do I need to use a blob? (I'm not overly familiar with either pickle or sqlite, so I wanted to make sure I'm barking up the right tree with some of my high-level design ideas.)

Answer 1

I needed to achieve the same thing too.

I turns out it caused me quite a headache before I finally figured out, thanks to this post, how to actually make it work in a binary format.

To insert/update:

pdata = cPickle.dumps(data, cPickle.HIGHEST_PROTOCOL) curr.execute("insert into table (data) values (:data)", sqlite3.Binary(pdata)) 

You must specify the second argument to dumps to force a binary pickling.
Also note the sqlite3.Binary to make it fit in the BLOB field.

To retrieve data:

curr.execute("select data from table limit 1") for row in curr:   data = cPickle.loads(str(row['data'])) 

When retrieving a BLOB field, sqlite3 gets a 'buffer' python type, that needs to be strinyfied using str before being passed to the loads method.

Answer 2

If you want to store a pickled object, you'll need to use a blob, since it is binary data. However, you can, say, base64 encode the pickled object to get a string that can be stored in a text field.

Generally, though, doing this sort of thing is indicative of bad design, since you're storing opaque data you lose the ability to use SQL to do any useful manipulation on that data. Although without knowing what you're actually doing, I can't really make a moral call on it.