Problem indexing add Simple Table Inherance

rubyonrails-talk
1

I have a simple table inherance, with an upper class GeneralElement. A class that inherits is Activity: class Activity < GeneralElement ... end

The GeneralElement table is very big (about 2.000.000 rows!). Other classes that inherit from GeneralElement return queries very fast, but Activity.last is very slow. I have added indexes to id and type, but it has no effect. What can I do?

I'll appreciate any help

2

You may want to grab the query that Activity.last is using, and try running it through 'EXPLAIN' to see what it's looking for. Have you defined an order (via default_scope, for instance) on Activity? You might need to have an index on that field together with 'type' to get right behavior.

--Matt Jones

3

Matt Jones wrote:

4

add_index will accept an array of columns:

add_index :general_elements, [:type, :id]

--Matt Jones