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  1. Performance Issue when using gin index

    谭忠涛 <zhongtao.tan@seaboxdata.com> — 2025-01-21T02:30:24Z

    The performance of creating a gin index before inserting data is different from that of inserting data after creating a gin index.
Case:
-- first make pg_trgm
create extension pg_trgm;
create table t1(a int, b varchar(20));
create index t1_b on t1 using gin(b gin_trgm_ops);
insert into t1 select a, a || substr('abcdefg', (random()*100000)::int%10000, 10) || a from generate_series(1,100000) t(a);
analyze t1;
explain analyze select * from t1 where b like '%abc%'; -- slow
reindex index t1_b;
explain analyze select * from t1 where b like '%abc%'; --&nbsp;normal





Regards



谭忠涛&nbsp; &nbsp;数据研究院数据库事业部
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  2. Re: Performance Issue when using gin index

    Tom Lane <tgl@sss.pgh.pa.us> — 2025-01-21T03:01:40Z

    "=?utf-8?B?6LCt5b+g5rab?=" <zhongtao.tan@seaboxdata.com> writes:
> The performance of creating a gin index before inserting data is different from that of inserting data after creating a gin index.

This isn't terribly surprising.  Read

https://www.postgresql.org/docs/current/gin.html#GIN-FAST-UPDATE

There's also useful info in

https://www.postgresql.org/docs/current/gin.html#GIN-TIPS

			regards, tom lane