RE: nextval(), and serial updates

Krishna,

In your example, by calling the "nextval()" function, you have just
incremented the sequence.  Every call to "nextval('sequence_name')", by
definition, increments sequence_name by one so, again referring to your
example, the next call to "currval()" correctly returns 2.

Phil Culberson
DAT Services

-----Original Message-----
From: Sampath, Krishna [mailto:KSampath@ekmail.com]
Sent: Tuesday, April 04, 2000 7:32 AM
To: pgsql-general
Subject: [GENERAL] nextval(), and serial updates



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