Postgresql 函数-事务隔离级别实践

过程大致意思：

验证：func 函数中依次调用 funca,funcb函数，三个函数中均有update操作，看看三个函数的select 是否可查看未提交的update

表：

CREATE TABLE public.audit
(
id text COLLATE pg_catalog."default",
name text COLLATE pg_catalog."default"
)

任意插入三行数据

定义三个函数如下：

-- FUNCTION: public.func()

-- DROP FUNCTION public.func();

CREATE OR REPLACE FUNCTION public.func(
)
RETURNS void
LANGUAGE 'plpgsql'

COST 100
VOLATILE
AS $BODY$

declare newid text = '10';
declare newname text='jack';

declare oldid text;
declare oldname text;
declare rowcursor refcursor;
begin
   update audit set id = newid,name = newname where 1=1;
   execute funca();
   execute funcb();
   --子事务update 在主事务中是否可以看到
   open rowcursor for select * from audit;
   loop
       fetch rowcursor into oldid,oldname;
       if found then
           raise notice 'func:id,name: %,%',oldid,oldname;
       else
       exit;
       end if;
   end loop;
   close rowcursor;
end;

$BODY$;

-- FUNCTION: public.funca()

-- DROP FUNCTION public.funca();

CREATE OR REPLACE FUNCTION public.funca(
)
RETURNS void
LANGUAGE 'plpgsql'

COST 100
VOLATILE
AS $BODY$

declare oldid text;
declare oldname text;
declare rowcursor refcursor;
begin
   --看看主事务的update 在子事务中是否勀查看
   open rowcursor for select * from audit;
   loop
       fetch rowcursor into oldid,oldname;
       if found then
       raise notice 'funca:id,name,state: %,%',oldid,oldname;
       else
       exit;
       end if;
   end loop;
   close rowcursor;
   --子事务更新，看看另一个子事务和主事务是否能看到
   update audit set id = '11' where id is not null;
end;

$BODY$;

-- FUNCTION: public.funcb()

-- DROP FUNCTION public.funcb();

CREATE OR REPLACE FUNCTION public.funcb(
)
RETURNS void
LANGUAGE 'plpgsql'

COST 100
VOLATILE
AS $BODY$

declare oldid text;
declare oldname text;
declare rowcursor refcursor;
begin
   --子事务a的update 在子事务b中是否查看
   open rowcursor for select * from audit;
   loop
       fetch rowcursor into oldid,oldname;
       if found then
           raise notice 'funcb:id,name,state: %,%',oldid,oldname;
       else
       exit;
       end if;
   end loop;
   close rowcursor;
end;

$BODY$;

ALTER FUNCTION public.funcb()
OWNER TO postgres;

执行结果，与你初始化的数据有关（事先插入了三行数据）

NOTICE: funca:id,name,state: 10,jack
NOTICE: funca:id,name,state: 10,jack
NOTICE: funca:id,name,state: 10,jack
NOTICE: funcb:id,name,state: 11,jack
NOTICE: funcb:id,name,state: 11,jack
NOTICE: funcb:id,name,state: 11,jack
NOTICE: func:id,name: 11,jack
NOTICE: func:id,name: 11,jack
NOTICE: func:id,name: 11,jack
结论：在read commited 与repeatable read 隔离级别下，均可相互看到未提交的update。异常回滚另验证

Postgresql 函数-事务隔离级别 实践

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