Query Caching

Query caching allows avoiding repeated queries to the database by caching the results locally for faster retrieval.

To enable queries, set the query cache local path in dj.config, create the directory, and activate the query caching.

# set the query cache path
dj.config['query_cache'] = os.path.expanduser('~/dj_query_cache')

# access the active connection object for the tables
conn = dj.conn() # if queries co-located with tables
conn = module.schema.connection # if schema co-located with tables
conn = module.table.connection # most flexible

# activate query caching for a namespace called 'main'
conn.set_query_cache(query_cache='main')

The query_cache argument is an arbitrary string serving to differentiate cache states; setting a new value will effectively start a new cache, triggering retrieval of new values once.

To turn off query caching, use the following:

conn.set_query_cache(query_cache=None)
# or
conn.set_query_cache()

While query caching is enabled, any insert or delete calls and any transactions are disabled and will raise an error. This ensures that stale data are not used for updating the database in violation of data integrity.

To clear and remove the query cache, use the following:

conn.purge_query_cache()