#
# This code will remove non-selecting/non-restricting joins from
-# {from} specs, aiding the RDBMS query optimizer.
+# {from} specs, aiding the RDBMS query optimizer
#
sub _prune_unused_joins {
- my $self = shift;
+ my ($self) = shift;
+
+ my ($from, $select, $where, $attrs) = @_;
- my $from = shift;
if (ref $from ne 'ARRAY' || ref $from->[0] ne 'HASH' || ref $from->[1] ne 'ARRAY') {
return $from; # only standard {from} specs are supported
}
- my $aliastypes = $self->_resolve_aliastypes_from_select_args($from, @_);
+ my $aliastypes = $self->_resolve_aliastypes_from_select_args(@_);
+
+ # a grouped set will not be affected by amount of rows. Thus any
+ # {multiplying} joins can go
+ delete $aliastypes->{multiplying} if $attrs->{group_by};
+
my @newfrom = $from->[0]; # FROM head is always present
my %need_joins = (map { %{$_||{}} } (values %$aliastypes) );
for my $j (@{$from}[1..$#$from]) {
push @newfrom, $j if (
- ! $j->[0]{-alias} # legacy crap
+ (! $j->[0]{-alias}) # legacy crap
||
$need_joins{$j->[0]{-alias}}
);
return \@newfrom;
}
-
#
# This is the code producing joined subqueries like:
# SELECT me.*, other.* FROM ( SELECT me.* FROM ... ) JOIN other ON ...
}
# construct the inner $from for the subquery
+ # we need to prune first, because this will determine if we need a group_bu below
my $inner_from = $self->_prune_unused_joins ($from, $inner_select, $where, $inner_attrs);
# if a multi-type join was needed in the subquery - add a group_by to simulate the
for my $type (keys %$aliases_by_type) {
for my $alias (keys %{$aliases_by_type->{$type}}) {
$aliases_by_type->{$type}{$_} = 1
- for (@{ $alias_list->{$alias}{-join_path} || [] });
+ for (map { keys %$_ } @{ $alias_list->{$alias}{-join_path} || [] });
}
}
# anyway, and deep cloning is just too fucking expensive
# So replace the first hashref in the node arrayref manually
my @new_from = ($from->[0]);
- my $sw_idx = { map { $_ => 1 } @$switch_branch };
+ my $sw_idx = { map { values %$_ => 1 } @$switch_branch };
for my $j (@{$from}[1 .. $#$from]) {
my $jalias = $j->[0]{-alias};