如何使用Plpgsql語言編寫尾遞歸？

Question

有些帖子說PostgreSQL的CTE基本上是迭代的，我不知道如何使用尾遞歸和plpgsql語言編寫查詢？

Answer 1

WITH RECURSIVE zzz AS (
     SELECT 11::integer AS val 
     UNION ALL 
     SELECT CASE WHEN (zzz.val %2 = 1) THEN 3*zzz.val+1 ELSE zzz.val/2 END AS val 
     FROM zzz 
     WHERE zzz.val <> 1 
     ) 
SELECT * FROM zzz;