#first performance problem #18

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gucki opened this Issue Jul 19, 2011 · 2 comments

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@gucki
gucki commented Jul 19, 2011

Using a simple Person.first seems to load all people in the database and then only use the first record.

Output from redis monitor when doing a Person.first with 3 records in the db:

+1311105369.469164 "smembers" "person🆔all"
+1311105369.469654 "hgetall" "person:1"
+1311105369.470109 "hgetall" "person:2"
+1311105369.470555 "hgetall" "person:3"

@whoahbot
Owner

There are many non-indexed uses of dm-redis that will incur a performance penalty based on the number of records, since the way that the adapter is currently written will fall-through to finding each record in the set of all records when a query has no other more optimal path to locating that record.

In the case of #first, I agree, there should be a more optimal path that the adapter uses to locate the first record, since loading each record is wasteful.

I'm not sure I'll have a chance to work on this in the near future, did you have a suggestion for improving the performance of #first?

@emiltin
emiltin commented Jul 21, 2015

In my app, Houses can have many Rooms. When i do house.rooms, I can see in redis-cli monitor that it fetches all (thousands) of rooms, even though only a few correct rooms are returned in the code. Of course this is very slow.

In House I have:
property :id, Serial, :index => true

Am I doing something wrong? Surely fetching all rows every time I just need the associated objects can't be right?

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