java - postgres 序列不递增

Question

我在 PostgreSQL 10.7 dB 上创建了一个名为 markush_seq 的 PostgreSQL 序列 我从序列中读取

select nextval('markush_seq’)` ) 

使用 Java Web 服务: 当我在 Eclipse 上运行 Web 服务(使用 java 1.8.161)或直接从 SQL 开发人员调用序列时，它工作正常并且序列每次递增 1，例如:

http://localhost:8086/wipdbws/read-markush-seq

21767823690

21767823691

21767823692

但是，当我在 AWS 上运行 Web 服务(使用 java 1.8.252)并使用以下命令读取 seq 时:

https://aws-location/wipdbws/read-markush-seq

我得到返回的序列号，例如:

21767823692

21767823702

21767823693

21767823703

21767823694

21767823704

AWS 中的序列似乎是 2 个递增序列的组合，间隔 10。 这是相同的 java 代码，唯一改变的是:

1. 网络服务的位置

   a. AWS – 美国西部

   b. Eclipse - 伦敦

2. Java 版本:

   a. 1.8.161 伦敦

   b.美国西部 1.8.252

序列详细信息是:

SELECT * FROM information_schema.sequences
where sequence_name='markush_seq';

select * from pg_sequences where sequencename='markush_seq';

任何建议表示赞赏。

Answer 1

可能是由于多个 session 访问序列和序列缓存设置。

Documentation说:

although multiple sessions are guaranteed to allocate distinct sequence values, the values might be generated out of sequence when all the sessions are considered. For example, with a cache setting of 10, session A might reserve values 1..10 and return nextval=1, then session B might reserve values 11..20 and return nextval=11 before session A has generated nextval=2. Thus, with a cache setting of one it is safe to assume that nextval values are generated sequentially; with a cache setting greater than one you should only assume that the nextval values are all distinct, not that they are generated purely sequentially. Also, last_value will reflect the latest value reserved by any session, whether or not it has yet been returned by nextval.