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这篇文章主要讲解了“怎么理解 PostgreSQL 创建数据表时的参数 fillfactor”,文中的讲解内容简单清晰,易于学习与理解,下面请大家跟着丸趣 TV 小编的思路慢慢深入,一起来研究和学习“怎么理解 PostgreSQL 创建数据表时的参数 fillfactor”吧!
下面创建不同 fillfactor 的数据表, 执行 update 操作
[local]:5432 pg12@testdb=# create table t_fillfactor_100(id int,c1 varchar(30),c2 varchar(30),c3 varchar(30)) with (fillfactor=100);
CREATE TABLE
Time: 2.462 ms
[local]:5432 pg12@testdb=# create table t_fillfactor_70(id int,c1 varchar(30),c2 varchar(30),c3 varchar(30)) with (fillfactor=70);
CREATE TABLE
Time: 3.437 ms
[local]:5432 pg12@testdb=# create table t_fillfactor_50(id int,c1 varchar(30),c2 varchar(30),c3 varchar(30)) with (fillfactor=50);
CREATE TABLE
Time: 28.553 ms
[local]:5432 pg12@testdb=# insert into t_fillfactor_100(id,c1,c2,c3) select x, c1 ||x, c2 ||x, c3 ||x from generate_series(1,1000000) as x;
INSERT 0 1000000
Time: 3583.216 ms (00:03.583)
[local]:5432 pg12@testdb=# insert into t_fillfactor_70(id,c1,c2,c3) select x, c1 ||x, c2 ||x, c3 ||x from generate_series(1,1000000) as x;
INSERT 0 1000000
Time: 6506.113 ms (00:06.506)
[local]:5432 pg12@testdb=# insert into t_fillfactor_50(id,c1,c2,c3) select x, c1 ||x, c2 ||x, c3 ||x from generate_series(1,1000000) as x;
INSERT 0 1000000
Time: 3113.901 ms (00:03.114)
[local]:5432 pg12@testdb=# update t_fillfactor_100 set c1=lpad(c1 ,30, c1),c2=lpad(c2 ,30, c2),c3=lpad( c3 ,30, c3
UPDATE 1000000
Time: 10641.794 ms (00:10.642)
[local]:5432 pg12@testdb=# update t_fillfactor_70 set c1=lpad(c1 ,30, c1),c2=lpad(c2 ,30, c2),c3=lpad( c3 ,30, c3
UPDATE 1000000
Time: 8563.046 ms (00:08.563)
[local]:5432 pg12@testdb=# update t_fillfactor_50 set c1=lpad(c1 ,30, c1),c2=lpad(c2 ,30, c2),c3=lpad( c3 ,30, c3
UPDATE 1000000
Time: 4036.735 ms (00:04.037)
可以看到, 在插入时,fillfactor 较高的数据表耗时较短, 而在 update 时 (全量),fillfactor 的则有较大的优势. 但, 经过多次 update 后, 耗时并不明显, 原因在于经过多次 update, 每个块的空闲空间跟 fillfactor=100 的设定已相差无几.
[local]:5432 pg12@testdb=# update t_fillfactor_100 set c1=lpad(c1 ,30, c1),c2=lpad(c2 ,30, c2),c3=lpad( c3 ,30, c3
UPDATE 1000000
Time: 4276.404 ms (00:04.276)
[local]:5432 pg12@testdb=# update t_fillfactor_70 set c1=lpad(c1 ,30, c1),c2=lpad(c2 ,30, c2),c3=lpad( c3 ,30, c3
UPDATE 1000000
Time: 3856.575 ms (00:03.857)
[local]:5432 pg12@testdb=# update t_fillfactor_50 set c1=lpad(c1 ,30, c1),c2=lpad(c2 ,30, c2),c3=lpad( c3 ,30, c3
UPDATE 1000000
Time: 4364.962 ms (00:04.365)
[local]:5432 pg12@testdb=#
重新创建表, 使用 pgbench 进行测试
[local]:5432 pg12@testdb=# drop table if exists t_fillfactor_100;
t,c1 varchar(30),c2 varchar(30),c3 varchar(30)) with (fillfactor=70);
create table t_fillfactor_50(id int,c1 varchar(30),c2 varchar(30),c3 varchar(30)) with (fillfactor=50);
insert into t_fillfactor_100(id,c1,c2,c3) select x, c1 ||x, c2 ||x, c3 ||x from generate_series(1,1000000) as x;
insert into t_fillfactor_70(id,c1,c2,c3) select x, c1 ||x, c2 ||x, c3 ||x from generate_series(1,1000000) as x;
insert into t_fillfactor_50(id,c1,c2,c3) select x, c1 ||x, c2 ||x, c3 ||x from generate_series(1,1000000) as x;
DROP TABLE
Time: 191.706 ms
[local]:5432 pg12@testdb=# drop table if exists t_fillfactor_70;
DROP TABLE
Time: 35.313 ms
[local]:5432 pg12@testdb=# drop table if exists t_fillfactor_50;
DROP TABLE
Time: 30.078 ms
[local]:5432 pg12@testdb=#
[local]:5432 pg12@testdb=# create table t_fillfactor_100(id int,c1 varchar(30),c2 varchar(30),c3 varchar(30)) with (fillfactor=100);
CREATE TABLE
Time: 40.443 ms
[local]:5432 pg12@testdb=# create table t_fillfactor_70(id int,c1 varchar(30),c2 varchar(30),c3 varchar(30)) with (fillfactor=70);
CREATE TABLE
Time: 1.334 ms
[local]:5432 pg12@testdb=# create table t_fillfactor_50(id int,c1 varchar(30),c2 varchar(30),c3 varchar(30)) with (fillfactor=50);
CREATE TABLE
Time: 1.024 ms
[local]:5432 pg12@testdb=#
[local]:5432 pg12@testdb=# insert into t_fillfactor_100(id,c1,c2,c3) select x, c1 ||x, c2 ||x, c3 ||x from generate_series(1,1000000) as x;
INSERT 0 1000000
Time: 2623.943 ms (00:02.624)
[local]:5432 pg12@testdb=# insert into t_fillfactor_70(id,c1,c2,c3) select x, c1 ||x, c2 ||x, c3 ||x from generate_series(1,1000000) as x;
INSERT 0 1000000
Time: 2543.045 ms (00:02.543)
[local]:5432 pg12@testdb=# insert into t_fillfactor_50(id,c1,c2,c3) select x, c1 ||x, c2 ||x, c3 ||x from generate_series(1,1000000) as x;
INSERT 0 1000000
Time: 2662.223 ms (00:02.662)
[local]:5432 pg12@testdb=#
使用 pgbench 进行测试
[pg12@localhost script]$ cat update_100.sql
\set id random(1,1000000)
begin;
update t_fillfactor_100 set c1=lpad(c1 ,30, c1),c2=lpad(c2 ,30, c2),c3=lpad(c3 ,30, c3) where id= :id;
[pg12@localhost script]$ cat update_70.sql
\set id random(1,1000000)
begin;
update t_fillfactor_70 set c1=lpad(c1 ,30, c1),c2=lpad(c2 ,30, c2),c3=lpad(c3 ,30, c3) where id= :id;
[pg12@localhost script]$ cat update_50.sql
\set id random(1,1000000)
begin;
update t_fillfactor_50 set c1=lpad(c1 ,30, c1),c2=lpad(c2 ,30, c2),c3=lpad(c3 ,30, c3) where id= :id;
[pg12@localhost script]$ pgbench -c 2 -C -f ~/script/update_100.sql -j 1 -n -T 60 -U pg12 testdb
transaction type: /home/pg12/script/update_100.sql
scaling factor: 1
query mode: simple
number of clients: 2
number of threads: 1
duration: 60 s
number of transactions actually processed: 691
latency average = 174.136 ms
tps = 11.485277 (including connections establishing)
tps = 11.625959 (excluding connections establishing)
[pg12@localhost script]$ pgbench -c 2 -C -f ~/script/update_70.sql -j 1 -n -T 60 -U pg12 testdb
transaction type: /home/pg12/script/update_70.sql
scaling factor: 1
query mode: simple
number of clients: 2
number of threads: 1
duration: 60 s
number of transactions actually processed: 652
latency average = 184.293 ms
tps = 10.852275 (including connections establishing)
tps = 10.981136 (excluding connections establishing)
[pg12@localhost script]$ pgbench -c 2 -C -f ~/script/update_50.sql -j 1 -n -T 60 -U pg12 testdb
transaction type: /home/pg12/script/update_50.sql
scaling factor: 1
query mode: simple
number of clients: 2
number of threads: 1
duration: 60 s
number of transactions actually processed: 627
latency average = 191.700 ms
tps = 10.432967 (including connections establishing)
tps = 10.551899 (excluding connections establishing)
[pg12@localhost script]$
使用 pgbench 使用随机值进行测试, 时长为 60s, 结果差别不大.
数据表大小的比较:
[local]:5432 pg12@testdb=# select pg_size_pretty(pg_relation_size( t_fillfactor_100
pg_size_pretty
----------------
58 MB
(1 row)
Time: 2.034 ms
[local]:5432 pg12@testdb=# select pg_size_pretty(pg_relation_size( t_fillfactor_70
pg_size_pretty
----------------
82 MB
(1 row)
Time: 1.469 ms
[local]:5432 pg12@testdb=# select pg_size_pretty(pg_relation_size( t_fillfactor_50
pg_size_pretty
----------------
117 MB
(1 row)
Time: 2.531 ms
[local]:5432 pg12@testdb=#
分别是 58MB vs 82MB vs 117MB ≈ 100 vs 70 vs 50
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