Storing R Objects in a relational database

Question

I frequently create nonparametric statistics (loess, kernel densities, etc) on data I pull out of a relational database. To make data management easier I would like to store

Answer 1

For sqlite (and possibly others):

CREATE TABLE data (blob BLOB);

Now in R:

RSQLite::dbGetQuery(db.conn, 'INSERT INTO data VALUES (:blob)', params = list(blob = list(serialize(some_object)))

Note the list wrapper around some_object. The output of serialize is a raw vector. Without list, the INSERT statement would be executed for each vector element. Wrapping it in a list allows RSQLite::dbGetQuery to see it as one element.

To get the object back from the database:

some_object <- unserialize(RSQLite::dbGetQuery(db.conn, 'SELECT blob FROM data LIMIT 1')$blob[[1]])

What happens here is you take the field blob (which is a list since RSQLite doesn't know how many rows will be returned by the query). Since LIMIT 1 assures only 1 row is returned, we take it with [[1]], which is the original raw vector. Then you need to unserialize the raw vector to get your object.