CREATE TEMP TABLE temp1 AS ( SELECT t::BIGINT AS id, ('data ' || t)::TEXT AS data FROM generate_series(1, 100) t);
CREATE TEMP TABLE temp2 AS ( SELECT t::BIGINT AS id, ('data ' || t)::TEXT AS data FROM generate_series(1, 100) t);

SELECT t1.id, t2.data FROM temp1 t1 LEFT JOIN temp2 AS t2 ON t1.id = t2.id;

EXPLAIN VERBOSE SELECT t1.id, t2.data FROM temp1 t1 LEFT JOIN temp2 AS t2 ON t1.id = t2.id;

                                     QUERY PLAN
------------------------------------------------------------------------------------
 Merge Left Join  (cost=161.29..268.01 rows=6728 width=40)
   Output: t1.id, t2.data
   Merge Cond: (t1.id = t2.id)
   ->  Sort  (cost=80.64..83.54 rows=1160 width=8)
         Output: t1.id
         Sort Key: t1.id
         ->  Seq Scan on pg_temp_19.temp1 t1  (cost=0.00..21.60 rows=1160 width=8)
               Output: t1.id
   ->  Sort  (cost=80.64..83.54 rows=1160 width=40)
         Output: t2.data, t2.id
         Sort Key: t2.id
         ->  Seq Scan on pg_temp_19.temp2 t2  (cost=0.00..21.60 rows=1160 width=40)
               Output: t2.data, t2.id
(13 rows)

CREATE TABLE img (
id BIGSERIAL NOT NULL PRIMARY KEY,
data BYTEA NOT NULL
);

CREATE TABLE img_meta (
id BEGSERIAL NOT NULL PRIMARY KEY,
data BYTEA NOT NULL
)

SELECT img.id, img.data AS img, img_meta.data AS meta FROM img LEFT JOIN img_meta ON img.id = img_meta.id

#!/usr/bin/perl

BEGIN {unshift @INC, '/home/warstone/DBD/Pg/dbdpg/blib/lib', '/home/warstone/DBD/Pg/dbdpg/blib/arch'}

use strict;
use warnings;
use DBI;
use DBD::Pg;
use Data::Dumper;

my $sql = "SELECT 1 AS one, i.id AS not_id, i.id + 1 AS wtf, i.ident AS jopa, il.level, il.max_items FROM inventory i LEFT JOIN inventory_level il ON i.id = il.inventory";

my $dbh = DBI->connect("dbi:Pg:dbname=farmstory", "farmstory", "", {AutoCommit => 1, RaiseError => 1});
my $sth = $dbh->prepare($sql);
$sth->execute;

my $data = $sth->pg_canonical_ids;
my $data2 = $sth->pg_canonical_names;

print "DBD::Pg version: $DBD::Pg::VERSION\nSQL: $sql\n\n";
print "Column names (\$sth->{NAME_lc}):\n" . Dumper($sth->{NAME_lc});
print "\nCanonical ids (\$sth->pg_canonical_ids, fast):\n". Dumper($data);
print "\nCanonical names (\$sth->pg_canonical_names, slow):\n" . Dumper($data2) . "\n";

warstone@dev:~/DBD/Pg/dbdpg$ perl test.pl
DBD::Pg version: 3.5.2
SQL: SELECT 1 AS one, i.id AS not_id, i.id + 1 AS wtf, i.ident AS jopa, il.level, il.max_items FROM inventory i LEFT JOIN inventory_level il ON i.id = il.inventory

Column names ($sth->{NAME_lc}):
$VAR1 = [
          'one',
          'not_id',
          'wtf',
          'jopa',
          'level',
          'max_items'
        ];

Canonical ids ($sth->pg_canonical_ids, fast):
$VAR1 = [
          undef,
          [
            24047,
            1
          ],
          undef,
          [
            24047,
            2
          ],
          [
            24055,
            3
          ],
          [
            24055,
            5
          ]
        ];

Canonical names ($sth->pg_canonical_names, slow):
$VAR1 = [
          undef,
          'public.inventory.id',
          undef,
          'public.inventory.ident',
          'public.inventory_level.level',
          'public.inventory_level.max_items'
        ];