use Carp::Clan qw/^DBIx::Class/;
#
+# This code will remove non-selecting/non-restricting joins from
+# {from} specs, aiding the RDBMS query optimizer
+#
+sub _prune_unused_joins {
+ my ($self) = shift;
+
+ my ($from, $select, $where, $attrs) = @_;
+
+ 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(@_);
+
+ # 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
+ ||
+ $need_joins{$j->[0]{-alias}}
+ );
+ }
+
+ return \@newfrom;
+}
+
+#
# This is the code producing joined subqueries like:
# SELECT me.*, other.* FROM ( SELECT me.* FROM ... ) JOIN other ON ...
#
];
}
-
# generate the inner/outer select lists
# for inside we consider only stuff *not* brought in by the prefetch
# on the outside we substitute any function for its alias
push @$inner_select, $sel;
}
-
- # scan the from spec against different attributes, and see which joins are needed
- # in what role
- my $inner_aliastypes =
- $self->_resolve_aliases_from_select_args( $from, $where, $inner_select, $inner_attrs );
- my $outer_aliastypes =
- $self->_resolve_aliases_from_select_args( $from, $where, $outer_select, $outer_attrs );
-
-
-
- # normalize a copy of $from, so it will be easier to work with further
- # down (i.e. promote the initial hashref to an AoH)
- $from = [ @$from ];
- $from->[0] = [ $from->[0] ];
-
-
# construct the inner $from for the subquery
- my %inner_joins = (map { %$_ } (values %$inner_aliastypes) );
- my @inner_from;
- for my $j (@$from) {
- push @inner_from, $j if $inner_joins{$j->[0]{-alias}};
- }
-
-
- # if a multi-type join was needed in the subquery ("multi" is indicated by
- # presence in {collapse}) - add a group_by to simulate the collapse in the subq
- unless ($inner_attrs->{group_by}) {
- for my $alias (keys %inner_joins) {
-
- # the dot comes from some weirdness in collapse
- # remove after the rewrite
- if ($attrs->{collapse}{".$alias"}) {
- $inner_attrs->{group_by} ||= $inner_select;
- last;
- }
- }
- }
+ # 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);
- # demote the inner_from head
- $inner_from[0] = $inner_from[0][0];
+ # if a multi-type join was needed in the subquery - add a group_by to simulate the
+ # collapse in the subq
+ $inner_attrs->{group_by} ||= $inner_select
+ if List::Util::first
+ { ! $_->[0]{-is_single} }
+ (@{$inner_from}[1 .. $#$inner_from])
+ ;
# generate the subquery
my $subq = $self->_select_args_to_query (
- \@inner_from,
+ $inner_from,
$inner_select,
$where,
$inner_attrs,
my $subq_joinspec = {
-alias => $attrs->{alias},
- -source_handle => $inner_from[0]{-source_handle},
+ -source_handle => $inner_from->[0]{-source_handle},
$attrs->{alias} => $subq,
};
# - it is part of the restrictions, in which case we need to collapse the outer
# result by tackling yet another group_by to the outside of the query
+ # normalize a copy of $from, so it will be easier to work with further
+ # down (i.e. promote the initial hashref to an AoH)
+ $from = [ @$from ];
+ $from->[0] = [ $from->[0] ];
+
# so first generate the outer_from, up to the substitution point
my @outer_from;
while (my $j = shift @$from) {
}
}
+ # scan the from spec against different attributes, and see which joins are needed
+ # in what role
+ my $outer_aliastypes =
+ $self->_resolve_aliastypes_from_select_args( $from, $outer_select, $where, $outer_attrs );
+
# see what's left - throw away if not selecting/restricting
# also throw in a group_by if restricting to guard against
# cross-join explosions
}
elsif ($outer_aliastypes->{restrict}{$alias}) {
push @outer_from, $j;
-
- # FIXME - this should be obviated by SQLA2, as I'll be able to
- # have restrict_inner and restrict_outer... or something to that
- # effect... I think...
-
- # FIXME2 - I can't find a clean way to determine if a particular join
- # is a multi - instead I am just treating everything as a potential
- # explosive join (ribasushi)
- #
- # if (my $handle = $j->[0]{-source_handle}) {
- # my $rsrc = $handle->resolve;
- # ... need to bail out of the following if this is not a multi,
- # as it will be much easier on the db ...
-
- $outer_attrs->{group_by} ||= $outer_select;
- # }
+ $outer_attrs->{group_by} ||= $outer_select unless $j->[0]{-is_single};
}
}
# happen is for it to fail due to an unqualified column, which in
# turn will result in a vocal exception. Qualifying the column will
# invariably solve the problem.
-sub _resolve_aliases_from_select_args {
- my ( $self, $from, $where, $select, $attrs ) = @_;
+sub _resolve_aliastypes_from_select_args {
+ my ( $self, $from, $select, $where, $attrs ) = @_;
$self->throw_exception ('Unable to analyze custom {from}')
if ref $from ne 'ARRAY';
# see what aliases are there to work with
my $alias_list;
- my @from = @$from; # if I don't copy weird shit happens
- for my $j (@from) {
+ for (@$from) {
+ my $j = $_;
$j = $j->[0] if ref $j eq 'ARRAY';
- $alias_list->{$j->{-alias}} = $j;
+ my $al = $j->{-alias}
+ or next;
+
+ $alias_list->{$al} = $j;
+ $aliases_by_type->{multiplying}{$al} = 1
+ unless $j->{-is_single};
}
# set up a botched SQLA
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};