The following bug has been logged on the website:
Bug reference: 16803
Logged by: osdba
Email address: mailtch@163.com
PostgreSQL version: 11.10
Operating system: CentOS7.6
Description:
create a table only one text/varchar colume, storage options
toast_tuple_target doesn't work, see:
[pg03@pgtrain pgdata]$ psql
psql (11.10)
Type "help" for help.
postgres=# create table test01(id int, t text);
CREATE TABLE
postgres=# alter table test01 set (toast_tuple_target=1024);
ALTER TABLE
postgres=# insert into test01 select seq, repeat('a', 1800) from
generate_series(1, 1000) as seq;
INSERT 0 1000
postgres=# select pg_total_relation_size('test01');
pg_total_relation_size
------------------------
2080768
(1 row)
postgres=# truncate table test01;
TRUNCATE TABLE
postgres=# insert into test01 select seq, repeat('a', 2800) from
generate_series(1, 1000) as seq;
INSERT 0 1000
postgres=# select pg_total_relation_size('test01');
pg_total_relation_size
------------------------
114688
(1 row)
because I set toast_tuple_target to 1024,so trigger toast compress when
insert data that length is 1800 or 2800, but only trigger toast compress
when data length is 2800.
when I create table have more than one text column, then storage options
toast_tuple_target can be work correctly:
postgres=# create table test01(id int, t1 text, t2 text);
CREATE TABLE
postgres=# alter table test01 set (toast_tuple_target=1024);
ALTER TABLE
postgres=# insert into test01 select seq, repeat('a', 1800), repeat('b',
1800) from generate_series(1, 1000) as seq;
INSERT 0 1000
postgres=# select pg_total_relation_size('test01');
pg_total_relation_size
------------------------
139264
(1 row)
postgres=# truncate table test01;
TRUNCATE TABLE
postgres=# insert into test01 select seq, repeat('a', 2800), repeat('b',
2800) from generate_series(1, 1000) as seq;
INSERT 0 1000
postgres=# select pg_total_relation_size('test01');
pg_total_relation_size
------------------------
163840
(1 row)
you can see, when table have two text column, then storage options
toast_tuple_target can be work correctly.
this is a bug?