derby 10.8.2.2 with sequences and currentvalue

[Yvan Sand]

hello, actually we use oracle and would like to use derby as the embedded db for our junit testing.

now we have a problem with sequences and I haven't found a solution yet, maybe we use it the wrong way?! I hope somebody can help...

we have the following sql script which creates two sequences and two tables. after that we insert some data using the sequences, but there is something wrong with the currentvalue...

CREATE sequence seq_type AS int start WITH 1; CREATE sequence seq_text AS int start WITH 1; CREATE TABLE t_type (id int PRIMARY KEY, label varchar (255)); CREATE TABLE t_text (id int PRIMARY KEY, text varchar(255), typeid int constraint type_fk REFERENCES t_type(id)); INSERT INTO t_type (id, label) VALUES (next value FOR seq_type, 'sample type'); SELECT * FROM t_type; -- data is inserted and id is 1 SELECT currentvalue FROM sys.syssequences WHERE sequencename='SEQ_TYPE'; -- this returns 6 but should be 1 !? INSERT INTO t_text (id, text, typeid) VALUES (next value FOR seq_text, 'first text', (SELECT currentvalue FROM sys.syssequences WHERE sequencename='SEQ_TYPE')); -- this is not working --> violation of foreign key constraint 'TYPE_FK' because currentvalue of SEQ_TYPE returns 6 and not 1 !?

the problem is that when calling "next value for seq_type" the sequence is ok and is incremented by 1, but the currentvalue is wrong and contains the value 6? when the sequence reaches 6, the currentvalue changes to 11.

can someone telling me what's going on and how must the script looks like to work correctly with sequences?

we're using derby 10.8.2.2 for this tests.

thanks for helping!

[Martin Vajsar]

Though I'm not acquianted with derby, it seems to me that you're fetching the "current value" from some dictionary table. You should use proper SQL construct for that. If next value FOR seq_text is valid on derby to fetch next value from a sequence, I'd say that current value FOR seq_text should provide you with the current value for your transaction.

Edit: I was probably assuming too much. From a quick peek into Derby documentation it seems there is no support for the "current value" of the sequence. The construct you're using is mentioned on forums, but the value is obtained from a dictionary view and is not mentioned in docs. I think this works for someone by accident, Derby sequences apparently were not designed to provide current values. You'll probably need to store the "next value" into a variable and use it with both parent and child tables.