sql - Postgres - 如何创建字母数字序列，如 AAAA0000 等

Question

我想创建一个这样的字母数字序列:

AAAA0000
AAAA0001
AAAA0002
AAAA0003
.
.
.
AAAA9999
AAAB0000
AAAB0001

等等

我已经创建了这个存储过程来做到这一点，但它太慢了:

CREATE OR REPLACE FUNCTION public.fn_batch_seq()
  RETURNS text
  LANGUAGE plpgsql
AS
$body$
DECLARE
  v_sequence TEXT := '';
  v_next_sequence TEXT := '';
  v_existing_id BIGINT := 0;
BEGIN

  /*
  *  VARCHAR BATCH SEQUENCE FOR SIMCARDS
  */
  SELECT "sequence" FROM batch_sequence WHERE id = 1 INTO v_sequence;
  IF v_sequence = '' THEN
    RAISE NOTICE 'Error - No existe ningun registro en batch_sequence almacenado';
    RETURN -500;
  END IF;
  SELECT perl_increment(v_sequence) INTO v_next_sequence;

  IF v_next_sequence = '' THEN
    RAISE NOTICE 'Error - La siguiente secuencia generada devolvio null o vacio';
    RETURN -500;
  END IF;


  UPDATE batch_sequence SET "sequence" = v_next_sequence WHERE id = 1;
  RETURN v_next_sequence;

  EXCEPTION WHEN OTHERS THEN
  /*
  * Other errors
  */
  RAISE NOTICE 'Error General - Posibles causas: No existe la tabla batch_sequence o no existe ningun registro en la misma';
  RETURN -500;

END;
$body$
  VOLATILE
  COST 100;

这个过程使用一个表来存储序列:

CREATE TABLE batch_sequence
(
   id        serial   NOT NULL,
   sequence  text     DEFAULT 'AAAA0000'::text NOT NULL
);

-- Column id is associated with sequence public.batch_sequence_id_seq

ALTER TABLE batch_sequence
   ADD CONSTRAINT batch_sequence_pk
   PRIMARY KEY (id);

为了增加序列，我使用了一个 perl 过程:

CREATE OR REPLACE FUNCTION public.perl_increment(text)
  RETURNS text
  LANGUAGE plperl
AS
$body$
my ($x) = @_;
    if (not defined $x) {
        return undef;
    }
    ++$x;
$body$
  VOLATILE
  COST 100;

对于大量数据，它工作起来非常慢，因为它必须在插入每一行之前执行。是否有另一种方法可以使用或不使用 Perl 来做到这一点？

请帮忙。

Answer 1

It works very slow with large amount of data, because it must be executed before inserting every single row. Is there another way to do that with or without Perl?

第一个选项:

创建一个序列并对其进行解码:

CREATE SEQUENCE my_serial START 11110000;

翻译成字母左边的部分:

select nextval(''my_serial'') INTO v_nextSeq ;
select translate(
       left( trim(to_char(v_nextSeq,'9999')), 4),
       '12345','ABCDE')
       ||
       right( trim(to_char(v_nextSeq,'9999')), 4);

第二个选项:

您可以保留所有序列号然后使用它:

**将used 字段添加到您的模式中，记得在序列上创建索引**:

CREATE TABLE batch_sequence
(
   id        serial   NOT NULL,
   sequence  text     DEFAULT 'AAA'::text NOT NULL,
   used      boolean  default false
);

填充整个表，这里简化为2位:

with s as (
  SELECT A.a || B.b  as sequence
  FROM unnest(string_to_array('A B C',' ')) A
  CROSS JOIN unnest(string_to_array('0 1 2 3 4 5 6 7 8 9',' ')) B
) 
insert into batch_sequence ( sequence )
select s.sequence
from s;

Check all is done :

select * from batch_sequence

Results :

| id | sequence |  used |
|----|----------|-------|
| 28 |       A0 | false |
| 29 |       A1 | false |
| 30 |       A2 | false |
| 31 |       A3 | false |
| 32 |       A4 | false |
| 33 |       A5 | false |
| 34 |       A6 | false |
| 35 |       A7 | false |
| 36 |       A8 | false |
| 37 |       A9 | false |
| 38 |       B0 | false |
| 39 |       B1 | false |
| 40 |       B2 | false |
| 41 |       B3 | false |
| 42 |       B4 | false |
| 43 |       B5 | false |
| 44 |       B6 | false |
| 45 |       B7 | false |
| 46 |       B8 | false |
| 47 |       B9 | false |
| 48 |       C0 | false |
| 49 |       C1 | false |
| 50 |       C2 | false |
| 51 |       C3 | false |
| 52 |       C4 | false |
| 53 |       C5 | false |
| 54 |       C6 | false |
| 55 |       C7 | false |
| 56 |       C8 | false |
| 57 |       C9 | false |

创建一个函数来获取新的序列号并将其设置为已使用。