metabase.query-processor.middleware.cache-backend.interface
Interface used to define different Query Processor cache backends. Defining a backend is straightforward: define a new namespace with the pattern
metabase.query-processor.middleware.cache-backend.<backend>
Where backend is a key representing the backend, e.g. db, redis, or memcached.
In that namespace, create an object that reifies (or otherwise implements) IQueryProcessorCacheBackend.
This object must be stored in a var called instance.
That's it. See metabase.query-processor.middleware.cache-backend.db for a complete example of how this is done.
Interface used to define different Query Processor cache backends. Defining a backend is straightforward: define a new namespace with the pattern metabase.query-processor.middleware.cache-backend.<backend> Where backend is a key representing the backend, e.g. `db`, `redis`, or `memcached`. In that namespace, create an object that reifies (or otherwise implements) `IQueryProcessorCacheBackend`. This object *must* be stored in a var called `instance`. That's it. See `metabase.query-processor.middleware.cache-backend.db` for a complete example of how this is done.
IQueryProcessorCacheBackendcljprotocol
Protocol that different Metabase cache backends must implement.
QUERY-HASH as passed below is a byte-array representing a 256-byte SHA3 hash; encode this as needed for use as a
cache entry key. RESULTS are passed (and should be returned) as a Clojure object, and individual backends are free
to encode this as appropriate when storing the results. (It's probably not a bad idea to compress the results; this
is what the :db backend does.)
Protocol that different Metabase cache backends must implement. QUERY-HASH as passed below is a byte-array representing a 256-byte SHA3 hash; encode this as needed for use as a cache entry key. RESULTS are passed (and should be returned) as a Clojure object, and individual backends are free to encode this as appropriate when storing the results. (It's probably not a bad idea to compress the results; this is what the `:db` backend does.)
cached-resultsclj
(cached-results this query-hash max-age-seconds)Return cached results for the query with byte array QUERY-HASH if those results are present in the cache and are less
than MAX-AGE-SECONDS old. Otherwise, return nil.
This method must also return a Timestamp from when the query was last ran. This must be assoced with the query results
under the key :updated_at.
(cached-results [_ query-hash max-age-seconds] (when-let [[results updated-at] (maybe-fetch-results query-hash max-age-seconds)] (assoc results :updated_at updated-at)))
Return cached results for the query with byte array QUERY-HASH if those results are present in the cache and are less
than MAX-AGE-SECONDS old. Otherwise, return `nil`.
This method must also return a Timestamp from when the query was last ran. This must be `assoc`ed with the query results
under the key `:updated_at`.
(cached-results [_ query-hash max-age-seconds]
(when-let [[results updated-at] (maybe-fetch-results query-hash max-age-seconds)]
(assoc results :updated_at updated-at)))save-results!clj
(save-results! this query-hash results)Add a cache entry with the RESULTS of running query with byte array QUERY-HASH.
This should replace any prior entries for QUERY-HASH and update the cache timestamp to the current system time.
(This is also an appropriate point to purge any entries older than the value of the query-caching-max-ttl Setting.)
Add a cache entry with the RESULTS of running query with byte array QUERY-HASH. This should replace any prior entries for QUERY-HASH and update the cache timestamp to the current system time. (This is also an appropriate point to purge any entries older than the value of the `query-caching-max-ttl` Setting.)
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