Expression Indexes

If you’re using functions in SQL queries, e.g. LOWER() or UPPER(), you need to be careful! When using a function to a select a column, existing indexes cannot be used! Create a functional index (an index on LOWER(column)).

Now this has been supported in rails for postgresql from version 7.0.4

create_table :users do |t|
  t.string :name
  t.index 'lower(name) varchar_pattern_ops'
end

Operator Classes

The operator class identifies the operators to be used by the index for that column. For example, a B-tree index on the type int4 would use the int4_ops class.

Before

The gist_trgm_ops after name is the operator class to use when using the index. Currently it’s possible to specify … USING gist (name) but there’s no way of adding the operator class after name.

After

Operator classes can be explicitly specified in add_index as:

add_index :users, :name, using: :gist, opclass: { name: :gist_trgm_ops }

In Schema CREATE INDEX users_name ON users USING gist (name gist_trgm_ops);