Thinking Sphinx & Rails questions

Question

I'm building my first Rails app and have it working great with Thinking Sphinx. I'm understanding most of it but would love it if someone could help me clarify a few conceptual questions

1. When displaying search results after a sphinx query, should I be using the sphinx_attributes that are returned from the sphinx query? Or should my view use normal rails objects, such as @property.title, @property.amenities.title etc? If I use normal rails objects, doesn't that mean its doing extra queries?

2. In a forum, I'd like to display 'unread posts'. Obviously this is true/false for each user/topic combination, so I'm thinking I should be caching the 'reader' ids within the topic's sphinx index. This way I can quickly do a query for all unread posts for a given user_id. I've got this working, but then realised its pointless, as there is a time delay between sphinx indexes. So if a user clicks on an unread post, it will still appear unread until the sphinx DB is re-indexed

3. I'm still on development so I'm manually indexing/rebuilding, but on production, what is a standard time between re-indexing?

4. I have a model with several text fields - should I concat these all into one column in the sphinx index for a keyword search? Surely this is quicker than indexing all the separate fields.

5. Slightly off-topic, but just wondering - when you access nested models, for example @property.agents.name, does this affect performance? Or does rails automatically fetch all associated entries when a property is pulled from the database?

Answer 1

To answer each of your points:

1. For both of your examples, sphinx_attributes would not be helpful. Firstly, you've already loaded the property, so the title is available directly without an extra database hit. And for property.amenities.title you're dealing with an array of strings, which Sphinx has no concept of. Generally, I would only use sphinx_attributes for complicated calculated attributes, not standard column references.

2. Yes, you're right, there will be a delay with this value.

3. It depends on how often your data changes. I have some apps where I can index every day because changes are so rare, but others where we'll run it every 10 minutes. If the data is particularly volatile, I'll look at using deltas (usually via Sidekiq) to have changes reflected in Sphinx in a few seconds.

4. I don't think it's much difference either way - unless you want to search on any of those columns separately? If so, it'll need to be a separate field.

5. By default, as you use each property's agents, the agents for that property will be loaded from the database (one SQL call per property). You could look at the eager loading docs for how to manage this better when you're dealing with multiple records. Thinking Sphinx has the ability to pass through :include options to the underlying ActiveRecord call.