Sequences - problem
Hallo!
I created several tables using a id-sequence for each:
create sequence portid;
create table ports(id integer primary key default nextval('portid'), name
varchar);
Now, since it is a web-application I am working on, I have several
Perl-scripts acting on/with the database.
THe informations-program simply has to read out each sequence in order to
give some statistical data about the database (number of ports, people
...)
As I try a
Pg::doQuery("select currval('portid');", \@ports);
the program gets no reply, on the Postmaster-task (I did not get
postmaster start on startup/background, runs on a task in foreground) I
that message:
ERROR: regionid.currval is not yet defined in this session
ERROR: jpid.currval is not yet defined in this session
ERROR: countri.currval is not yet defined in this session
ERROR: jprid.currval is not yet defined in this session
ERROR: portid.currval is not yet defined in this session
What does the problem consist in, and how can I solve it?
In my opinion it is better to read out the counter instead of querying all
elements in a table, so to get the number of elements ...
Pg::doQuery("select * from ports;", \@ports);
Where the number I am looking for is $#ports then ...
I think this method will take a lot of time and is not very effective, as
I do not think I wil ever access one of the entrys read (at least not
while putting some information) ...
Saluti!
Ludwig
Now, since it is a web-application I am working on, I have several
Perl-scripts acting on/with the database.THe informations-program simply has to read out each sequence in order to
give some statistical data about the database (number of ports, people
...)As I try a
Pg::doQuery("select currval('portid');", \@ports);
the program gets no reply, on the Postmaster-task (I did not get
postmaster start on startup/background, runs on a task in foreground) I
that message:
ERROR: regionid.currval is not yet defined in this session
ERROR: jpid.currval is not yet defined in this session
ERROR: countri.currval is not yet defined in this session
ERROR: jprid.currval is not yet defined in this session
ERROR: portid.currval is not yet defined in this session
You cannot call currval on a sequence you have not nextval-ed at least
once in your session. There was a discussion of the a few weeks (I think)
back. currval is defined to give you the value of the sequence most
recently given to your session, not the current/highest value of the
sequence especially since that value may never actually go into a table.
In addition, the sequence value is not a good representation of number
of rows anyway, since you may have deleted rows or non-committed rows
(errors, rollback). If you want number of rows in table, you want
select count(*) from table.
Hallo!
In addition, the sequence value is not a good representation of number
of rows anyway, since you may have deleted rows or non-committed rows
(errors, rollback). If you want number of rows in table, you want
select count(*) from table.
thx! Seems to work fine!
Saluti!
Ludwig