任何一個關系型數(shù)據(jù)庫關于模糊匹配（like)的優(yōu)化都是一件痛苦的事，相對而言，諸如like ‘abc%’之類的還好一點，可以通過創(chuàng)建索引來優(yōu)化，但對于like ‘c%’之類的，真的就沒有辦法了。

這里介紹一種postgresql關于like ‘c%’的優(yōu)化方法，是基于全文檢索的特性來實現(xiàn)的。

測試數(shù)據(jù)準備（環(huán)境centos6.5 + postgresql 9.6.1）。

postgres=# create table ts(id int,name text);
CREATE TABLE
postgres=# d ts
Table “public.ts”
Column | Type | Modifiers
——–+———+———–
id | integer |
name | text |
postgres=# insert into ts select n,n||’_pjy’ from generate_series(1,2000) n;
INSERT 0 2000
postgres=# insert into ts select n,n||’_mdh’ from generate_series(1,2000000) n;
INSERT 0 2000000
postgres=# insert into ts select n,n||’_lmm’ from generate_series(1,2000000) n;
INSERT 0 2000000
postgres=# insert into ts select n,n||’_syf’ from generate_series(1,2000000) n;
INSERT 0 2000000
postgres=# insert into ts select n,n||’_wbd’ from generate_series(1,2000000) n;
INSERT 0 2000000
postgres=# insert into ts select n,n||’_hhh’ from generate_series(1,2000000) n;
INSERT 0 2000000
postgres=# insert into ts select n,n||’_sjw’ from generate_series(1,2000000) n;
INSERT 0 2000000
postgres=# insert into ts select n,n||’_jjs’ from generate_series(1,2000000) n;
INSERT 0 2000000
postgres=# insert into ts select n,n||’_ymd’ from generate_series(1,2000000) n;
INSERT 0 2000000
postgres=# insert into ts select n,n||’_biu’ from generate_series(1,2000000) n;
INSERT 0 2000000
postgres=# insert into ts select n,n||’_dfl’ from generate_series(1,2000000) n;
INSERT 0 2000000
postgres=# select count(*) from ts;
count
———-
20002000
(1 row)