我有一个包含 220 万行的表。
Table "public.index"
Column | Type | Modifiers
-----------+-----------------------------+-----------------------------------------------------
fid | integer | not null default nextval('index_fid_seq'::regclass)
location | character varying |
Indexes:
"index_pkey" PRIMARY KEY, btree (fid)
"location_index" btree (location text_pattern_ops)
该位置是文件的完整路径，但我需要使用文件所在文件夹的名称进行查询。该文件夹名称在表中是唯一的。
为了避免%一开始，我搜索我知道的完整路径：
select fid from index where location like '/path/to/folder/%'
解释分析：
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Seq Scan on index (cost=0.00..120223.34 rows=217 width=4) (actual time=1181.701..1181.701 rows=0 loops=1)
Filter: ((location)::text ~~ '/path/to/folder/%'::text)
Rows Removed by Filter: 2166034
Planning time: 0.954 ms
Execution time: 1181.748 ms
(5 rows) …