PostgreSQL arrays and DBD

[Alex Cheshev]

Hello.

I create a table:

CREATE TABLE groups (
  group_id serial PRIMARY KEY,
  name varchar(64) UNIQUE NOT NULL,
  guests integer[] DEFAULT '{}'
)

I add a new record to the table:

INSERT INTO groups (name) VALUES ('My friends');

Now the table contains 1 record:

| group_id |    name    | guests
+----------+------------+--------
|        1 | My friends | {}

I read the new record from the table using DBI:

my $sth = $dbh->prepare(qq/SELECT * FROM groups/);
$sth->execute();
my (@guests, $group);
push(@guests, $group) while $group = $sth->fetchrow_hashref(); # Line 4
print $guests[0]->{guests}->[0]; # Why ({group_id=>1, name=>'My friends', guests=>[0]}) ?

Output of the script:

Argument "" isn't numeric in null operation at ./guestmanager.pl line 4
0

DBD should return a reference to an empty array. But DBD returned the reference to the array containing 1 element (0). How can I have a different result:

({group_id=>1, name=>'My friends', guests=>[]})

PS
Version of DBD::Pg is 2.9.0 .

[Decibel!]

Don't know the answer, but I'm betting that Dave does :)

On Aug 14, 2008, at 3:31 AM, Александр Чешев wrote:

> I create a table:
>
> CREATE TABLE groups (
>   group_id serial PRIMARY KEY,
>   name varchar(64) UNIQUE NOT NULL,
>   guests integer[] DEFAULT '{}'
> )
>
> I add a new record to the table:
>
> INSERT INTO groups (name) VALUES ('My friends');
>
> Now the table contains 1 record:
>
> | group_id |    name    | guests
> +----------+------------+--------
> |        1 | My friends | {}
>
> I read the new record from the table using DBI:
>
> my $sth = $dbh->prepare(qq/SELECT * FROM groups/);
> $sth->execute();
> my (@guests, $group);
> push(@guests, $group) while $group = $sth->fetchrow_hashref(); #  
> Line 4
> print $guests[0]->{guests}->[0]; # Why ({group_id=>1, name=>'My  
> friends', guests=>[0]}) ?
>
> Output of the script:
>
> Argument "" isn't numeric in null operation at ./guestmanager.pl  
> line 4
> 0
>
> DBD should return a reference to an empty array. But DBD returned  
> the reference to the array containing 1 element (0). How can I have  
> a different result:
>
> ({group_id=>1, name=>'My friends', guests=>[]})
>
> PS
> Version of DBD::Pg is 2.9.0 .

--
Decibel!, aka Jim C. Nasby, Database Architect  decibel@...
Give your computer some brain candy! www.distributed.net Team #1828

[Greg Sabino Mullane]

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> DBD should return a reference to an empty array. But DBD returned
> the reference to the array containing 1 element (0). How can I have
> a different result:

This was fixed: version 2.9.2 of DBD::Pg should behave as you expect
with regards to empty integer arrays. This was asked and answered
on the dbi list, but no ccs went to the interfaces list - sorry about that.

http://www.nntp.perl.org/group/perl.dbi.users/2008/08/msg33162.html


- --
Greg Sabino Mullane greg@...
End Point Corporation
PGP Key: 0x14964AC8 200808221317
http://biglumber.com/x/web?pk=2529DF6AB8F79407E94445B4BC9B906714964AC8
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