I don't think duplicating the data won't work because then I'll be
doing 2 writes for every turn of the game, and I need that to be fast.
I don't mind if fetching a user's game list is a little bit slow, but
5-20 seconds is too much. I can denormalize all the data such that
Game 2 fields for each entry in PlayerGameState if that helps, but I'd
still like to know why it's so slow now.
I do have appstat installed. For one particular misbehaving request,
the query fetches 5 PlayerGameState records. It iterates through the
first 4 taking ~20 ms each, then I see a RunQuery taking 8 seconds.
I don't see an easy way to export appstat data, but I can include more
details if necessary.
Here's the query code in question.
Set<Key> myUserCache = Sets.newHashSet();
Query query = pm.newQuery(PlayerGameState.class);
query.declareParameters(
"com.google.appengine.api.datastore.Key userKeyParam");
query.setFilter("userKey == userKeyParam");
List<PlayerGameState> playerStates =
(List<PlayerGameState>) query.execute(playerKey);
List<Game> games = Lists.newArrayList();
for (PlayerGameState playerState : playerStates) {
Game game = playerState.getGame();
myUserCache.add(game.getPlayerState().getUserKey());
myUserCache.add(game.getOpponentState().getUserKey());
games.add(game);
}
On May 3, 1:16 am, "Ikai L (Google)" <[email protected]> wrote:
> Indexes don't work the same way they do in relational databases. If you can
> fetch a value with a query, that likely means an index exists on that
> property. In a relational database, when an index is not present, the
> database will do a full table scan.
>
> A fetch by Key is always fast. Have you considered storing multiple games
> inside a single Game instance? Or simply storing the data you need both in
> the Game instances? If you want to cut down on request latency, do as many
> by key gets as possible. Don't try to approach the modeling from a
> normalization perspective. How many entities are you retrieving? And have
> you tried looking at what's happening via AppStats yet
> (http://code.google.com/appengine/docs/java/tools/appstats.html)?
>
>
>
>
>
> On Fri, Apr 30, 2010 at 1:54 AM, Philip Tucker <[email protected]> wrote:
> > I've got a Game object that includes two PlayerGameState objects. Both
> > are persistence-capable. My query fetches all PlayerGameState objects
> > for a particular user, then I get the associated game and other
> > player. The initial fetch is always fast, and the entire operation is
> > generally lass than a second. But periodically, maybe 5 of the time,
> > it takes much longer, from 5-20 seconds. It's not fetching the
> > PlayerGameState objects that's slow, it's accessing
> > PlagerGameState.game and Game.playerStates.
>
> > I shouldn't need to add an index on the keys, should I? I'd like to
> > fetch the Game objects directly but as far as I can tell we can't
> > query on a joined table; ie, I can't do something like "select from
> > Game, PlayerGameState join on PlayerGameState.game where
> > PlayerGameState.userKey == userKeyParam".
>
> > @PersistenceCapable(identityType = IdentityType.APPLICATION)
> > public class Game {
> > �...@primarykey
> > �...@persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
> > private Key key;
>
> > �...@persistent(mappedBy = "game")
> > �...@element(dependent = "true")
> > private List<PlayerGameState> playerStates;
>
> > ...
> > }
>
> > @PersistenceCapable(identityType = IdentityType.APPLICATION)
> > public class PlayerGameState {
> > �...@suppresswarnings("unused")
> > �...@primarykey
> > �...@persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
> > private Key key;
>
> > �...@persistent
> > private Key userKey;
>
> > �...@persistent
> > private Game game;
>
> > ...
> > }
>
> > --
> > You received this message because you are subscribed to the Google Groups
> > "Google App Engine for Java" group.
> > To post to this group, send email to
> > [email protected].
> > To unsubscribe from this group, send email to
> > [email protected]<google-appengine-java%2B
> > [email protected]>
> > .
> > For more options, visit this group at
> >http://groups.google.com/group/google-appengine-java?hl=en.
>
> --
> Ikai Lan
> Developer Relations, Google App Engine
> Twitter:http://twitter.com/ikai
> Delicious:http://delicious.com/ikailan
>
> ----------------
> Google App Engine links:
> Blog:http://googleappengine.blogspot.com
> Twitter:http://twitter.com/app_engine
> Reddit:http://www.reddit.com/r/appengine
>
> --
> You received this message because you are subscribed to the Google Groups
> "Google App Engine for Java" group.
> To post to this group, send email to [email protected].
> To unsubscribe from this group, send email to
> [email protected].
> For more options, visit this group
> athttp://groups.google.com/group/google-appengine-java?hl=en.
--
You received this message because you are subscribed to the Google Groups
"Google App Engine for Java" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/google-appengine-java?hl=en.
