Re: MySQL LAST_INSERT_ID() to Postgres

Scott Marlowe wrote:
> On Thu, Aug 28, 2008 at 3:38 PM, Bill <pg(at)dbginc(dot)com> wrote:
>
>> I am new to PostgreSQL but it seems to me that lastval() will only work if
>> the insert does not produce side effects that call nextval(). Consider the
>> case where a row is inserted into a table that has an after insert trigger
>> and the after insert trigger inserts a row into another table which has a
>> serial primary key. In that case I assume that lastval() will return the
>> value from the serial column in the second table.
>>
>
> No, setval, currval, and lastval all require as an argument a sequence
> name. So the real issue is you have to know the sequence name to use
> them.
>
> The problem with lastval is that it reports the last value that the
> sequence gave out whether it was to us or someone else. this makes it
> NOT SAFE for concurrent transactions, but more for maintenance work.
>
> I use returning almost exclusively now.
>
>
The PostgresSQL 8.3 help file clearly shows that lastval() does not take
a sequence as a parameter and the description i is "Return the value
most recently returned by |nextval| in the current session. This
function is identical to |currval|, except that instead of taking the
sequence name as an argument it fetches the value of the last sequence
that |nextval| was used on in the current session. It is an error to
call |lastval| if |nextval| has not yet been called in the current
session." Is the help incorrect?

Bill