Proper full text index Rails/PostgreSQL/pg_search

Question

I am testing performance for PostgreSQL full text search (using pg_search gem) and solr (sunspot_solr gem).

For 4 million records I am getting 13456 ms for

Answer 1

This expression:

to_tsvector('simple', (COALESCE(title::TEXT), ''))

is not sargable against your index.

You should declare the index on the exactly that expression which is used in the query:

CREATE INDEX products_gin_title
ON products
USING GIN(to_tsvector('simple', COALESCE(title::TEXT,'')))

(or make ruby generate the expression which is used in the index).

If you want multiple columns to be indexed, just concatenate them:

CREATE INDEX products_gin_title
ON products
USING GIN(to_tsvector('simple', title || ' ' || product_type || ' ' || platform_id))

but again, Ruby should be filtering on exactly same expression for the index to be of use.