Is there a concise way to select the nextval for a PostgreSQL sequence multiple times in 1 query? This would be the only value being returned.
For example, I would like to do something really short and sweet like:
SELECT NEXTVAL('mytable_seq', 3) AS id;
And get:
id
-----
118
119
120
(3 rows)
select nextval('mytable_seq') from generate_series(1,3);
generate_series is a function which returns many rows with sequential numbers, configured by it's arguments.
In above example, we don't care about the value in each row, we just use generate_series as row generator. And for each row we can call nextval. In this case it returns 3 numbers (nextvals).
You can wrap this into function, but I'm not sure if it's really sensible given how short the query is.
There is a great article about this exact problem: "getting multiple values from sequences".
If performance is not an issue, for instance when using the sequence values dwarfs the time used to get them or n is small, then the SELECT nextval('seq') FROM generate_series(1,n) approach is the simplest and most appropriate.
But when preparing data for bulk loads the last approach from the article of incrementing the sequence by n from within a lock is appropriate.
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