POSTGRESQL的分区和MYSQL不同,MYSQL是有专门的分区表,而POSTGRESQL的分区则利用它本身的面向对象的特性来做。下面我们来简单的体验下。我们先创建一张父表。记
POSTGRESQL的分区和MYSQL不同,MYSQL是有专门的分区表, 而POSTGRESQL的分区则利用它本身的面向对象的特性来做。 下面我们来简单的体验下。
我们先创建一张父表。 记住,所有的分区表都得继承他。
t_girl=# create table num_master (id int not null primary key);CREATE TABLE接下来我们创建一个简单的函数来动态创建分区表。
t_girl=# create or replace function create_partition_table () returns void as $$t_girl$# declare i int;t_girl$# declare cnt int;t_girl$# declare stmt text;t_girl$# begint_girl$# -- Created by ytt at 2013/12/15. Dynamic creating partition tables.t_girl$# i:= 0;t_girl$# cnt:=4;t_girl$# <> while i < cnt loopt_girl$# stmt := 'create table num_slave'||i+1||'(check(id >='||i*100||' and id <'||(i+1)*100||')) inherits(num_master)';t_girl$# execute stmt;t_girl$# i:=i + 1;t_girl$# end loop lable1;t_girl$# return;t_girl$# end;t_girl$# $$ language plpgsql;CREATE FUNCTIONt_girl=#OK。 现在可以执行了。
t_girl=# select create_partition_table(); create_partition_table------------------------(1 row)列出所有的表
t_girl=# \dList of relations Schema | Name | Type | Owner --------+------------+-------+---------- ytt | num_master | table | postgres ytt | num_slave1 | table | postgres ytt | num_slave2 | table | postgres ytt | num_slave3 | table | postgres ytt | num_slave4 | table | postgres ytt | t1| table | t_girl(6 rows)我们针对父表建立一个触发器函数体,对应其分区表的数据分布。
t_girl=# create or replace function num_insert_trigger()t_girl-# returns trigger as $$t_girl$# begint_girl$# -- Created by ytt at 2013/12/15. Do how to distribute data.t_girl$# if (new.id >=0 and new.id <100) thent_girl$# insert into num_slave1 values (new.*);t_girl$# elsif (new.id >=100 and new.id <200) thent_girl$# insert into num_slave2 values(new.*);t_girl$# elsif (new.id >=200 and new.id <300) thent_girl$# insert into num_slave3 values (new.*);t_girl$# elsif (new.id >=300 and new.id <400) thent_girl$# insert into num_slave4 values (new.*);t_girl$# elset_girl$# raise exception 'Column id out of range.';t_girl$# end if;t_girl$# return null;t_girl$# end;t_girl$# $$t_girl-# language plpgsql;CREATE FUNCTION我们看看已经建好的触发器:
t_girl=# \d+ num_masterTable "ytt.num_master" Column | Type | Modifiers | Storage | Stats target | Description--------+---------+-----------+---------+--------------+------------- id| integer | not null | plain ||Indexes:"num_master_pkey" PRIMARY KEY, btree (id)Triggers:insert_num_slave_trigger BEFORE INSERT ON num_master FOR EACH ROW EXECUTE PROCEDURE ytt.num_insert_trigger()Child tables: num_slave1,num_slave2,num_slave3,num_slave4Has OIDs: no我们现在生成简单的测试数据。
t_girl=# select func_create_sample_data(); func_create_sample_data-------------------------(1 row)上面的函数生成了大概400行的数据。
为了查看优化器是如何处理查询的,我们来看看简单的查询
t_girl=# explain select * from num_master where id > 30 and id < 120;QUERY PLAN----------------------------------------------------------------- Append (cost=0.00..5.00 rows=91 width=4) -> Seq Scan on num_master (cost=0.00..0.00 rows=1 width=4)Filter: ((id > 30) AND (id < 120)) -> Seq Scan on num_slave1 (cost=0.00..2.50 rows=70 width=4)Filter: ((id > 30) AND (id < 120)) -> Seq Scan on num_slave2 (cost=0.00..2.50 rows=20 width=4)Filter: ((id > 30) AND (id < 120))(7 rows)t_girl=#我也是今天刚刚接触到POSTGRESQL的分区表,有问题,还希望提出。
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