PostgreSQL位元影像索引

 　　什麼是位元影像索引?

　　位元影像索引的一些特性?

　　位元影像索引的優缺點?

　　來看下位元影像掃描的例子。

　　QUERY PLAN ------------------------------------------------------------------------------------------------------------------------- ------------------- Bitmap Heap Scan on bitmap_test (cost=2023.16..4157.75 rows=99967 width=4) (actual time=24.373..41.054 rows=100000 loop s=1) Recheck Cond: (is_visible = 'yes'::bpchar) -> Bitmap Index Scan on idx_bitmap_is_visible (cost=0.00..1998.17 rows=99967 width=0) (actual time=24.252..24.252 ro ws=100000 loops=1) Index Cond: (is_visible = 'yes'::bpchar) Total runtime: 47.175 ms (5 rows) Time: 47.725 ms