KingbaseES例程_普通表在线转分区表（基于规则）

KingbaseES例程_普通表在线转分区表

概述

普通表转分区表，使用视图的替换式规则，以路由方式，实现在线转移数据。

数据准备

/*普通大表*/
create table tab_single
as
select id, (random() * 100)::int + 1 c1, md5(id::text) name
from generate_series(1, 10000000) id;

alter table tab_single add primary key (id);

/*表结构一样的分区表*/
create table tab_part
( like tab_single )
partition by list (c1)
;
select format($$ create table tab_part_%s partition of tab_part for values in ( %s ) $$, id, id)
from generate_series(1, 100) id \gexec

/*分区表可以创建查询所需的索引*/
create index idx_tab_part_id on tab_part(id);

/*创建合并视图，作为操作入口*/
create or replace view tab_view as
select *
from tab_single
union all
select *
from tab_part;

/*视图不可更新*/
update tab_view
set name = 'a'
where id = 1;
[55000] ERROR: cannot update view "tab_view" 详细：Views containing UNION, INTERSECT, or EXCEPT are not automatically updatable. 建议：To enable updating the view, provide an INSTEAD OF UPDATE trigger or an unconditional ON UPDATE DO INSTEAD rule.

通过规则实现视图更新

INSERT 规则

/*NEW数据，插入到分区表*/
CREATE or replace RULE rul_ins_tab_view
    AS ON INSERT TO tab_view
    DO INSTEAD insert into tab_part
               select new.*;

insert into tab_view
select id + 10000000, (random() * 100)::int + 1 c1, 'a' name
from generate_series(1, 10) id;

/*新数据插入到分区表*/
select count(*) from tab_part;
 count
-------
    10
(1 row)

DELETE 规则

CREATE or replace RULE rul_del_tab_view
    AS ON DELETE TO tab_view
    DO INSTEAD (
    delete
    from tab_single
    where row (tab_single.*) = row (old.*) ;
    delete
    from tab_part
    where row (tab_part.*) = row (old.*);
    );

delete
from tab_view
where id = 10;

/*旧数据从普通表删除*/
select *
from tab_single
where id = 10;
 id | c1 | name
----+----+------
(0 rows)

UPDATE 规则

/*
* 1. 更新分区表的数据
* 2. 如果分区表没有旧数据，则分区表插入新新数据
* 3. 删除普通表的旧数据
*/

CREATE or replace RULE rul_upd_tab_view
    AS ON UPDATE TO tab_view
    DO INSTEAD (
    insert into tab_part
    select new.*
    where (select count(*) cnt
           from tab_part
           where row (tab_part.*) = row (new.*)) = 0;

    delete
    from tab_single
    where row (tab_single.*) = row (old.*);

    delete
    from tab_part
    where row (tab_part.*) = row (old.*)
      and row (tab_part.*) != row (new.*)
      and old <> new;
    );

/*更新在普通表数据，可以更新主键值*/
update tab_view
set name='abcde'
where id = 200;

/*数据从普通表删除*/
select id, c1, name
from tab_single
where id = 200; id | c1 | name
----+----+------
(0 rows)

/*数据在分区表中插入或更新*/
select id, c1, name
from tab_part
where id = 200;
 id  | c1 | name
-----+----+-------
 200 | 89 | abcde
(1 row)

/*更新在分区表数据，可以更新主键值*/
update tab_view
set id=20000000+200 ,
    name='xxxxxxxx'
where id = 200;

/*在分区表的数据*/
select id, c1, name
from tab_part
where id = 200;
    id    | c1 |   name
----------+----+----------
 20000200 | 52 | xxxxxxxx
(1 row)

分步转移数据

do
$$
    declare
        stprow int;
        chgrow int;
        movrow int;

        timstm timestamp;
    begin
        stprow := 10000; /*每步迁移10000行数据*/
        chgrow := 0; /*实际影响的行*/
        movrow := 0; /*累计迁移的行*/

        loop
            timstm := clock_timestamp();
            with del as (delete from tab_single
                where ctid = any (array(select ctid from tab_single limit stprow))
                returning *)
            insert into tab_part
            select * from del;
            commit;
            get diagnostics chgrow = row_count;
            exit when chgrow = 0;
            movrow := movrow + chgrow;
            raise info 'moved rows : % / % , % ms',chgrow, movrow,  (date_part('sec',clock_timestamp()-timstm)*1000)::numeric(10,3);
        end loop;

    end;
$$
;

SHELL脚本高并发迁移数据

time seq 0 1000 | xargs -i -n1 -P10 psql -c "update tab_view set id = id where id between 10000*{}+0 and 10000*({}+1)-1"

real    0m49.630s
user    0m0.740s
sys     0m1.315s

抛弃普通表，保留分区表

/*分区表代替视图*/
do
$$
    begin
        drop view tab_view;
        alter table tab_part
            rename to tab_view;
        commit;
    end;
$$
;

或者

/*保留数据入口视图，删除视图的规则，修改视图定义*/
do
$$
    begin
        drop  RULE rul_ins_tab_view TO tab_view;
        drop  RULE rul_del_tab_view TO tab_view;
        drop  RULE rul_upd_tab_view TO tab_view;

        create or replace view tab_view as
        select *
        from tab_part;

        commit;
    end;
$$
;

注意

DML操作，主键值可能会出现重复，但可以通过校验语句避免。