Explicitly Use Index For EXPLAIN in PostgreSQL

Sometimes when checking the EXPLAIN of a query results in a sequential scan where you expected an index to be used. This is expected as an optimization of PostgreSQL to decide which is the best method to use.

                                    QUERY PLAN
-----------------------------------------------------------------------------------
 Seq Scan on widgets  (cost=0.00..70.92 rows=1038 width=402)
   Filter: ((deleted_at IS NULL) AND ((widget_type)::text = 'foo'::text))

But what if you WANT to see how the index will be used? Well you can force sequential scanning to be turned off.

SET enable_seqscan TO off;

Now if we view the query plan again we can see the index in use.

                                    QUERY PLAN
-----------------------------------------------------------------------------------------------
 Bitmap Heap Scan on widgets  (cost=32.87..100.76 rows=1038 width=402)
   Recheck Cond: ((widget_type)::text = 'foo'::text)
   Filter: (deleted_at IS NULL)
   ->  Bitmap Index Scan on index_widgets_on_widget_type  (cost=0.00..32.61 rows=1111 width=0)
         Index Cond: ((widget_type)::text = 'foo'::text)

Hooray!

Now just don't forget to re-enable the previous functionality

SET enable_seqscan TO on;