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I’m using GAE/Java with Objectify, and I’m trying to find the fastest way to check if a given object exists in the datastore, given the key. What I’m doing right now is .get(key) with @Cached on, but either way that still retrieves the entire object, which is unnecessary.
Any ideas on how to do this with an index only hit? I was also thinking of a keys only query, but I’m seeing (on the system status dashboard ) that the latency is much more than a get.
A keys-only query is the only way to get an index-only hit. Whether it’s faster than a get depends on the size of your entity and the size of your index. In a trivial example, I’m getting around 8ms for a get and 13ms for a query. You can use AppStats to figure out which is cheaper for you with real data.