Re: simple function index question

Interestingly a version of this:

 

CREATE INDEX TX_QSET_DIR_MAP_PRI_URI_TYP_UK

  ON tx_question_set_dir_map

  USING btree

  (question_set2tx_question_set ,uri_type,

  (CASE WHEN uri_type = 201900 THEN null::varchar(100)

     ELSE question_set_dir_map_key END);

 

Worked for me.  Try it if you are still interested.

Just do proper casting of null (it was varchar(100) in my case).