以下爲本次演示的樣例表結構以及數據。
t_girl=# \d insert_ignore
Table "ytt.insert_ignore"
Column | Type | Modifiers
----------+------------------------+-----------
id | integer | not null
log_time | time without time zone |
Indexes:
"insert_ignore_pkey" PRIMARY KEY, btree (id)
t_girl=# select * from insert_ignore;
id | log_time
----+----------------
1 | 14:44:12.37185
(1 row)
我來演示下幾種代替方法。
第一種方法, 用自帶的規則(RULE)來實現。
t_girl=# create rule r_insert_ignore as on insert to insert_ignore where exists (select 1 from insert_ignore where id = new.id) do instead nothing;
CREATE RULE
這時,我們插入兩條記錄,其中一條的主鍵值已經存在,直接忽略掉。 實際插入的記錄數爲1.
t_girl=# insert into insert_ignore values(1,current_time),(2,current_time);
INSERT 0 1
t_girl=# select * from insert_ignore;
id | log_time
----+-----------------
1 | 14:44:12.37185
2 | 14:48:22.222848
(2 rows)
第二種方法, 建立一個返回NULL的觸發器函數。 那麼函數體如下:
t_girl=# create or replace function sp_insert_ignore() returns trigger as
$ytt$
begin
perform 1 from insert_ignore where id = new.id;
if found then
return null;
end if;
return new;
end;
$ytt$ language 'plpgsql';
CREATE FUNCTION
對應的觸發器如下:
t_girl=# create trigger tr_ib_insert_ignore before insert on insert_ignore for each row execute procedure sp_insert_ignore();
CREATE TRIGGER
繼續插入兩條記錄。
t_girl=# insert into insert_ignore values (3,current_time),(2,current_time);
INSERT 0 1
t_girl=# select * from insert_ignore;
id | log_time
----+-----------------
1 | 14:44:12.37185
2 | 14:48:22.222848
3 | 15:05:33.198847
(3 rows)
OK。目的達到了。
第三種方法,用WITH來實現。
t_girl=# insert into insert_ignore
with ytt_test(f1,f2) as (
values(6,current_time),(3,current_time)
)
select a.* from ytt_test as a where a.f1 not in (select id from insert_ignore as b);
INSERT 0 1
查看記錄,插入了一條ID爲6的記錄,忽略了ID爲3的記錄。
t_girl=# select * from insert_ignore;
id | log_time
----+-----------------
1 | 14:44:12.37185
2 | 14:48:22.222848
3 | 15:05:33.198847
6 | 15:15:52.297802
(4 rows)
第四種,用存儲過程來代替INSERT處理。
t_girl=# create or replace function sp_insert_ignore (
IN f_id int,
IN f_log_time time without time zone
) returns void as
$ytt$
begin
insert into insert_ignore values (f_id,f_log_time);
exception when unique_violation then
raise notice 'Duplicated Key Error on ID:%',f_id;
return;
end;
$ytt$ language plpgsql;
第一次調用,拋出了錯誤。
t_girl=# select sp_insert_ignore(1,'14:22:35'::time);
NOTICE: Duplicated Key Error on ID:1
sp_insert_ignore
------------------
(1 row)
第二次正常插入。
t_girl=# select sp_insert_ignore(8,'14:22:35'::time);
sp_insert_ignore
------------------
(1 row)
t_girl=# select * from insert_ignore;
id | log_time
----+-----------------
1 | 14:44:12.37185
2 | 14:48:22.222848
3 | 15:05:33.198847
6 | 15:15:52.297802
8 | 14:22:35
(5 rows)
t_girl=#
OK,目的也達到了。