Re: nextval(), and serial updates
От | Silvio Macedo |
---|---|
Тема | Re: nextval(), and serial updates |
Дата | |
Msg-id | Pine.GSO.4.10.10004041827530.16502-100000@tanya обсуждение исходный текст |
Ответ на | nextval(), and serial updates ("Sampath, Krishna" <KSampath@ekmail.com>) |
Список | pgsql-general |
Hi! In my opinion there is absolutely no doubt that this is the intended behavior. When you do select nextval you are saying: INCREMENT THE COUNTER TO THE NEXT VALUE. When you do currval, currval should (and does) give you the most up to date value in YOUR session. I guess that when an INSERT in a table with a sequence field is processed, postgres will internally execute select nextval() - like a trigger. And, also, the implementation of serial values probably assumes that you don't call nextval yourself, unless you really know what you are doing... Regards, Silvio On Tue, 4 Apr 2000, Sampath, Krishna wrote: > > Normally, currval() points to the index sequence for the last inserted > record. > > However, after I call > select nextval('i_seq'::text) > on the serial data tyep i_seq, the counter gets incremented by 1. The next > INSERT skips a number in the sequence. Is this by design? I was a bit > surprized because the currval() gets incremented also, and you no longer > point to the last inserted record. > > puzzled, > krishna > > concrete example: > create table t1 ( i serial, s varchar(20) ); -- create table > insert into t1 (s) values ('first line'); -- insert 1 record > select * from t1; -- gives (1 > row) > select currval('t1_i_seq'); -- gives 1 as > currval .. ok > select nextval('t1_i_seq'); -- gives 2 as > nextval .. ok so far > select currval('t1_i_seq'); -- gives 2 as > currval ... should this be 1? > insert into t1 (s) values ('second line'); -- inserts second line, > serial id set to 3 > select * from t1; -- (2 rows) > i is now 3, should be 2 > > > ``````````` Silvio Emanuel Nunes Barbosa de Macedo (PhD Std) ''''''''''''' smacedo@ic.ac.uk smacedo@inescn.pt Intelligent and Interactive Systems Telecom. and Multimedia Imperial College, University of London INESC Porto Exhibition Road, Pc da Republica, 93 London SW7 2AZ, England 4050-497 Porto Portugal Tel:+44 171 5946323 Tel:+351 22 2094220
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