在Ruby on Rails应用程序中将表分成3个表

Question

I have a class called Stream that has many records in the database, and many more are constantly being added to it. A field in the streams table called rating can be -1, 0, 1, or be null. I will say "rated" as having rating -1, 0, or 1, and "unrated" as having a null rating. As of right now, there are 24M records in the streams table. 20M are rated, 4M are unrated. The streams table needs to be queried often for the unrated records. The problem is, it takes time to query such a large table.

I thought of breaking up the streams table into 3 separate tables. There could be a rated streams table, an unrated streams table, and an old unrated streams table. The way it would work would be, a new stream is created. New records are unrated, so it would be placed in the unrated streams table. If it is rated, it would be moved to the rated streams table. If it is unrated for more than a week, it would be moved to the old unrated streams table. I would still need to be able to use methods and associations from the Stream class seamlessly, like:

buzz.rated_streams.first
interest.unrated_streams.first
user.old_streams.first
RatedStream.find(1).buzz
UnratedStream.find(2).interest
OldStream.find(3).user

The unrated streams table could be queried much faster. The rated streams table would be useful for analysis. The old unrated streams table would be a dump for old data.

I have some questions. Would breaking up the table be a good idea? If so, how would I do it to keep everything from breaking, and use the same methods and associations from the Stream class? If breaking up the table is a bad idea, what should I do instead?

Answer 1

I think this is a baaaaad idea. A lot of custom code (which is not guaranteed to work).

You should create an index on rating instead. This will likely solve all your problems with queries (you might want to make it covered also).

Answer 2

A good design depends on why you need to frequently query for a boolean property with 4 million matches. Are you maintaining a to-do list of streams to rate? Are you showing a "number of unrated streams" counter? Are you querying by some other property as well?

Assuming the first, you could do something like

• Have most of the information about a stream in the streams table.
• Create a streams_ratings table which belongs_to :streams and has the rating
• Create streams_tasks table which belongs_to :streams and has the priority, the assigned rater, the assignment date, etc. Index by assignee.
• Find a stream that needs to be rated with StreamTask.first(:assignee => 'unassigned').stream . You can used a named scope to make this smoother.
• When you're done, create a new StreamRating and delete the StreamTask

Answer 3

不确定您使用的是哪个数据库，但您可以对表进行分区以帮助提高性能。

Answer 4

There turned out to be another way to write the query I was running that was so slow. Instead of this which took 2 minutes or more:

user.streams.unrated.all( :conditions => "", :order => "id DESC", :limit => 10 )

This works almost instantly:

user.streams.unrated.find( :all, :conditions => "", :order => "id DESC", :limit => 10 )

I don't know what the difference could be. I gave Sergio the check since his was the best answer.