POSTGRESQL 分區表初次體驗

POSTGRESQL的分區和MYSQL不同，MYSQL是有專門的分區表， 而POSTGRESQL的分區則利用它本身的面向對象的特性來做。 下面我們來簡單的體驗下。


我們先創建一張父表。 記住，所有的分區表都得繼承他。

t_girl=# create table num_master (id int not null primary key);
CREATE TABLE

接下來我們創建一個簡單的函數來動態創建分區表。

t_girl=# create or replace function create_partition_table () returns void as $$
t_girl$# declare i int;
t_girl$# declare cnt int;
t_girl$# declare stmt text;
t_girl$# begin
t_girl$# -- Created by ytt at 2013/12/15. Dynamic creating partition tables.
t_girl$# i:= 0;
t_girl$# cnt:=4;
t_girl$# <<lable1>> while i < cnt loop
t_girl$#   stmt := 'create table num_slave'||i+1||'(check(id >='||i*100||' and id <'||(i+1)*100||')) inherits(num_master)';
t_girl$#   execute stmt;
t_girl$#   i:=i + 1;
t_girl$# end loop lable1;
t_girl$# return;
t_girl$# end;
t_girl$# $$ language plpgsql;
CREATE FUNCTION
t_girl=# 

OK。 現在可以執行了。

t_girl=# select create_partition_table();
 create_partition_table 
------------------------
 
(1 row)

列出所有的表

t_girl=# \d
           List 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)

我們針對父表建立一個觸發器函數體，對應其分區表的數據分佈。

t_girl=# create or replace function num_insert_trigger()
t_girl-# returns trigger as $$
t_girl$# begin
t_girl$# -- Created by ytt at 2013/12/15. Do how to distribute data.
t_girl$# if (new.id >=0 and new.id <100) then
t_girl$# insert into num_slave1 values (new.*);
t_girl$# elsif (new.id >=100 and new.id <200) then
t_girl$# insert into num_slave2 values(new.*);
t_girl$# elsif (new.id >=200 and new.id <300) then
t_girl$# insert into num_slave3 values (new.*);
t_girl$# elsif (new.id >=300 and new.id <400) then
t_girl$# insert into num_slave4 values (new.*);
t_girl$# else
t_girl$# raise exception 'Column id out of range.';
t_girl$# end if;
t_girl$# return null;
t_girl$# end;
t_girl$# $$
t_girl-# language plpgsql;
CREATE FUNCTION

我們看看已經建好的觸發器：

t_girl=# \d+ num_master
                       Table "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_slave4
Has OIDs: no

我們現在生成簡單的測試數據。

t_girl=# select func_create_sample_data();
 func_create_sample_data 
-------------------------
 
(1 row)

上面的函數生成了大概400行的數據。




爲了查看優化器是如何處理查詢的，我們來看看簡單的查詢

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=# 

我也是今天剛剛接觸到POSTGRESQL的分區表，有問題，還希望提出。