4-2-3. Index Only Scan의 Heap Fetches

-- [SQL-4-2-3-a] EXPLAIN (ANALYZE,BUFFERS,COSTS OFF) SELECT t1.ord_no FROM startdbpg.tr_ord t1 WHERE t1.ord_no BETWEEN 10 AND 19;

-- [SQL-4-2-3-b] UPDATE startdbpg.tr_ord t1 SET ord_no = t1.ord_no + 0 WHERE t1.ord_no BETWEEN 10 AND 19;

-- [SQL-4-2-3-c]: [SQL-4-2-3-a]를 재실행 -- [SQL-4-2-3-a] EXPLAIN (ANALYZE,BUFFERS,COSTS OFF) SELECT t1.ord_no FROM startdbpg.tr_ord t1 WHERE t1.ord_no BETWEEN 10 AND 19;

-- [SQL-4-2-3-d]: 베큠 후 [SQL-4-2-3-a]를 재실행 VACUUM startdbpg.tr_ord; -- [SQL-4-2-3-a] EXPLAIN (ANALYZE,BUFFERS,COSTS OFF) SELECT t1.ord_no FROM startdbpg.tr_ord t1 WHERE t1.ord_no BETWEEN 10 AND 19;