为什么oracle序列在设置为1时增加2？

Question

so this is perplexing me.. so I got this syntax in my JPA code: (which I follow instructions and the syntax is correct)

 @SequenceGenerator(name="oracle_gen", sequenceName="TEST_SEQ", allocationSize=1)
 @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="oracle_gen")

where I got a sequence in my Oracle 10 named "TEST_SEQ" which is set to increment by 1

It works now.. but when it inserts my row, the ID column (where the sequence is set to) increase by 2.. like 17, 19, 21, etc..

When I did select test_seq.nextval from dual from oracle, it currently say 22 but I know if I add another row from my java application, it'll be 23.. I can't figure out why and where it is adding another 1. The sequence is already set to NOCACHE (in Oracle).. what am I doing wrong? Help! :(

Ok.. this is so odd.. I just realized whenever I do a select test_seq.nextval, it keep increasing my value?! I do have a trigger on the database. Is that what's causing it? sorry, I'm new to Oracle/pl/sql.

thanks for any help.

Answer 1

You're possibly misusing NEXTVAL. From Using Sequences (emphasis mine):

A sequence is referenced in SQL statements with the NEXTVAL and CURRVAL pseudocolumns; each new sequence number is generated by a reference to the sequence pseudocolumn NEXTVAL, while the current sequence number can be repeatedly referenced using the pseudo-column CURRVAL.