nextval()
Synopsis
Use the nextval( sequence_name ) function to return the next value from the sequence cache for the current session. If no more values are available in the cache, the session allocates a block of numbers for the cache and returns the first one. The number of elements allocated is determined by the cache option specified as part of the CREATE SEQUENCE statement.
Semantics
sequence_name
Specify the name of the sequence.
- An error is raised if a sequence reaches its minimum or maximum value.
Examples
Create a simple sequence that increments by 1 every time nextval() is called
yugabyte=# CREATE SEQUENCE s;
CREATE SEQUENCE
Call nextval() a couple of times.
yugabyte=# SELECT nextval('s');
nextval
---------
1
(1 row)
yugabyte=# SELECT nextval('s');
nextval
---------
2
(1 row)
Create a sequence with a cache of 3 values
yugabyte=# CREATE SEQUENCE s2 CACHE 3;
CREATE SEQUENCE
In the same session, call nextval(). The first time it's called, the session's cache will allocate numbers 1, 2, and 3. This means that the data for this sequence will have its last_val set to 3. This modification requires two RPC requests.
SELECT nextval('s2');
nextval
---------
1
(1 row)
The next call of nextval() in the same session will not generate new numbers for the sequence, so it is much faster than the first nextval() call because it will just use the next value available from the cache.
SELECT nextval('s2');
nextval
---------
2
(1 row)