我在使用PostgreSQL中的触发器创建条形码时遇到问题。问题是,当客户端访问我的Web应用程序并同时插入数据时,我需要在我的目标项目中生成条形码。但问题是自动生成的条形码是重复的。任何解决方案,请帮助我。格式条形码为: 2016000000001 。 这是我的触发器:
DROP TABLE IF EXISTS "test"."barcode";
CREATE TABLE "test"."barcode" (
"id" int8 DEFAULT nextval('"test".t_id_seq'::regclass) NOT NULL,
"barcode" varchar(255) COLLATE "default"
)
WITH (OIDS=FALSE);
-----------------------------------------
CREATE OR REPLACE FUNCTION test.my_trigger_function()
RETURNS trigger AS
$BODY$DECLARE new_barcode CHAR(50);
BEGIN
SELECT
(CASE
WHEN
CHAR_LENGTH (CAST(CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1 AS CHAR(20))) = 1 THEN
(SUBSTRING(barcode, 1, 4) || '00000000' || CAST((CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1) AS CHAR(20)))
WHEN
CHAR_LENGTH (CAST(CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1 AS CHAR(20))) = 2 THEN
(SUBSTRING(barcode, 1, 4) || '0000000' || CAST((CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1) AS CHAR(20)))
WHEN
CHAR_LENGTH (CAST(CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1 AS CHAR(20))) = 3 THEN
(SUBSTRING(barcode, 1, 4) || '000000' || CAST((CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1) AS CHAR(20)))
WHEN
CHAR_LENGTH (CAST(CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1 AS CHAR(20))) = 4 THEN
(SUBSTRING(barcode, 1, 4) || '00000' || CAST((CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1) AS CHAR(20)))
WHEN
CHAR_LENGTH (CAST(CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1 AS CHAR(20))) = 5 THEN
(SUBSTRING(barcode, 1, 4) || '0000' || CAST((CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1) AS CHAR(20)))
WHEN
CHAR_LENGTH (CAST(CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1 AS CHAR(20))) = 6 THEN
(SUBSTRING(barcode, 1, 4) || '000' || CAST((CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1) AS CHAR(20)))
WHEN
CHAR_LENGTH (CAST(CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1 AS CHAR(20))) = 7 THEN
(SUBSTRING(barcode, 1, 4) || '00' || CAST((CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1) AS CHAR(20)))
WHEN
CHAR_LENGTH (CAST(CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1 AS CHAR(20))) = 8 THEN
(SUBSTRING(barcode, 1, 4) || '0' || CAST((CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1) AS CHAR(20)))
WHEN
CHAR_LENGTH (CAST(CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1 AS CHAR(20))) = 9 THEN
(SUBSTRING(barcode, 1, 4) || CAST((CAST(SUBSTRING(barcode, 5, 9) AS INTEGER) + 1) AS CHAR(20)))
ELSE
(CAST((CAST(TO_CHAR(NOW(),'yyyy') AS INTEGER)+1) AS CHAR(20)) || '000000001')
END
) INTO new_barcode
FROM
test. barcode
ORDER BY
id DESC
LIMIT 1;
IF new_barcode IS NULL THEN
new_barcode = (CAST(TO_CHAR(NOW(),'yyyy') AS CHAR(20)) || '000000001');
END IF;
NEW.barcode = new_barcode;
RETURN NEW;
END;$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
ALTER FUNCTION test.my_trigger_function()
OWNER TO postgres;
--------------------------------------------------
CREATE TRIGGER "my_trigger" BEFORE INSERT ON "test"."barcode"
FOR EACH ROW
EXECUTE PROCEDURE "test"."my_trigger_function"();
答案 0 :(得分:1)
(我的眼睛流血......)这是你可以做的,只需使用SEQUENCE(保证不会产生任何重复):
CREATE SEQUENCE IF NOT EXISTS test.barcode_seq START 2016000000001;
CREATE OR REPLACE FUNCTION test.my_trigger_function() RETURNS trigger AS
$BODY$
DECLARE
_barcode bigint;
BEGIN
_barcode := nextval('test.barcode_seq');
IF EXTRACT('year' FROM CURRENT_DATE) <> _barcode/1000000000 THEN
_barcode := EXTRACT('year' FROM CURRENT_DATE) * 1000000000 + 1;
PERFORM setval('test.barcode_seq', _barcode, true);
END IF;
NEW.barcode = _barcode::text;
RETURN NEW;
END;
$BODY$ LANGUAGE plpgsql;
答案 1 :(得分:0)
试试这个:
创建一个序列:
create sequence test.barcode_sequence_byyear start 1;
和您的触发器功能:
CREATE OR REPLACE FUNCTION test.my_trigger_function()
RETURNS trigger AS
$BODY$DECLARE new_barcode CHAR(50);
declare count_barcode_of_year integer;
BEGIN
--If it is the first barcode of year then init sequence to 1
select count(*) into count_barcode_of_year from test.barcode where barcode like to_char(now(),'YYYY')||'%';
if count_barcode_of_year=0 then
--set sequence to 1
PERFORM setval('test.barcode_sequence_byyear'::regclass,1,false);
end if;
--Format your new barcode with year and sequence ( YEAR + Sequence with 9 significatives zeros :
NEW.barcode=to_char(now(),'YYYY')||to_char(nextval('test.barcode_sequence_byyear'::regclass),'FM'||repeat('0',9));
RETURN NEW;
END;$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
ALTER FUNCTION test.my_trigger_function()
OWNER TO postgres;