任何一個(gè)關(guān)系型數(shù)據(jù)庫(kù)關(guān)于模糊匹配（like)的優(yōu)化都是一件痛苦的事，相對(duì)而言，諸如like ‘abc%’之類的還好一點(diǎn)，可以通過(guò)創(chuàng)建索引來(lái)優(yōu)化，但對(duì)于like ‘c%’之類的，真的就沒(méi)有辦法了。

這里介紹一種postgresql關(guān)于like ‘c%’的優(yōu)化方法，是基于全文檢索的特性來(lái)實(shí)現(xiàn)的。

測(cè)試數(shù)據(jù)準(zhǔn)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)