Postgresql中的松散索引扫描-选择其他列？

Question

postgresql中没有松散的索引扫描，但是this stack overflow page描述了一种使用递归CTE扫描进行自我滚动的好方法。我的问题是：如何选择其他列（distinct子句中未使用）？

这是我当前正在运行的代码：SELECT distinct on (HLH_EVNT_SK, DX_CD) HLH_EVNT_SK, DX_CD, DX_VRSN_ID, DX_TP_CD from med_clm_dx_final;可以，但是速度很慢。

（HLH_EVNT_SK，DX_CD）在表med_clm_dx_final上定义一个索引；

为了加快速度，我可以像这样实现递归CTE

WITH RECURSIVE
     t AS (
  select HLH_EVNT_SK, DX_CD from (select HLH_EVNT_SK, DX_CD from med_clm_dx_final order by HLH_EVNT_SK, DX_CD limit 1) asdf union all 
  select (select HLH_EVNT_SK from med_clm_dx_final where (HLH_EVNT_SK, DX_CD) > (t.HLH_EVNT_SK,t.DX_CD) order by HLH_EVNT_SK, DX_CD limit 1),
         (select DX_CD from med_clm_dx_final where (HLH_EVNT_SK, DX_CD) > (t.HLH_EVNT_SK,t.DX_CD) order by HLH_EVNT_SK, DX_CD limit 1) 
     from t where t.HLH_EVNT_SK is not null)  
select * from t where t.HLH_EVNT_SK is not null

但是我不知道如何选择不包含在选择中的其他列，即DX_VRSN_ID和DX_TP_CD。谢谢！