Support retrieving value from any sequence

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От Thom Brown
Тема Support retrieving value from any sequence
Дата
Msg-id CAA-aLv5ntC3TOmduvEgLRH+R08r3GtZ8e3a3j5rcjwuwygDjzw@mail.gmail.com
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Ответы Re: Support retrieving value from any sequence
Re: Support retrieving value from any sequence
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Hi all,

When using currval() to find the current value of all sequences, it chokes on those that aren't initialised.  This is expected and documented as behaving in this manner.  However, I think it would be useful to also support retrieving the current value of a sequence, regardless of whether it's been used.  As this wouldn't be to get a sequence value for the current session, but all sessions, this would ideally get the real current value.

The use-case I have in mind is for finding out how close to the 32-bit integer limit sequences have reached.  At the moment, this isn't possible without creating a custom function to go fetch the last_value from the specified sequence.

So would it be desirable to have a function which accepts a sequence regclass as a parameter, and returns the last_value from the sequence?

Effectively, the same result as what this provides:

CREATE FUNCTION lastval(tablename regclass) RETURNS bigint AS $$
DECLARE
  last_value bigint;
BEGIN
  EXECUTE format('SELECT last_value FROM %I ', tablename) INTO last_value USING tablename;
  RETURN last_value;
END
$$ LANGUAGE plpgsql;

Thom

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