X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FDBIx%2FClass%2FStorage%2FDBIHacks.pm;h=4b66c4ebf65c80fae8414dde5c40a4e601bc89f1;hb=48580715af3072905f2c71dc27e7f70f21a11338;hp=a54477e071b5251b90056b5a59699e8d59292d1d;hpb=09e14fdcc53797129436ace4fc16f64e6f750a75;p=dbsrgits%2FDBIx-Class.git diff --git a/lib/DBIx/Class/Storage/DBIHacks.pm b/lib/DBIx/Class/Storage/DBIHacks.pm index a54477e..4b66c4e 100644 --- a/lib/DBIx/Class/Storage/DBIHacks.pm +++ b/lib/DBIx/Class/Storage/DBIHacks.pm @@ -16,6 +16,40 @@ use mro 'c3'; 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 ... # @@ -46,7 +80,6 @@ sub _adjust_select_args_for_complex_prefetch { ]; } - # 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 @@ -63,113 +96,21 @@ sub _adjust_select_args_for_complex_prefetch { push @$inner_select, $sel; } - # 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] ]; - my %original_join_info = map { $_->[0]{-alias} => $_->[0] } (@$from); - - - # decide which parts of the join will remain in either part of - # the outer/inner query - - # First we compose a list of which aliases are used in restrictions - # (i.e. conditions/order/grouping/etc). Since we do not have - # introspectable SQLA, we fall back to ugly scanning of raw SQL for - # WHERE, and for pieces of ORDER BY in order to determine which aliases - # need to appear in the resulting sql. - # It may not be very efficient, but it's a reasonable stop-gap - # Also unqualified column names will not be considered, but more often - # than not this is actually ok - # - # In the same loop we enumerate part of the selection aliases, as - # it requires the same sqla hack for the time being - my ($restrict_aliases, $select_aliases, $prefetch_aliases); - { - # produce stuff unquoted, so it can be scanned - my $sql_maker = $self->sql_maker; - local $sql_maker->{quote_char}; - my $sep = $self->_sql_maker_opts->{name_sep} || '.'; - $sep = "\Q$sep\E"; - - my $non_prefetch_select_sql = $sql_maker->_recurse_fields ($inner_select); - my $prefetch_select_sql = $sql_maker->_recurse_fields ($outer_attrs->{_prefetch_select}); - my $where_sql = $sql_maker->where ($where); - my $group_by_sql = $sql_maker->_order_by({ - map { $_ => $inner_attrs->{$_} } qw/group_by having/ - }); - my @non_prefetch_order_by_chunks = (map - { ref $_ ? $_->[0] : $_ } - $sql_maker->_order_by_chunks ($inner_attrs->{order_by}) - ); - - - for my $alias (keys %original_join_info) { - my $seen_re = qr/\b $alias $sep/x; - - for my $piece ($where_sql, $group_by_sql, @non_prefetch_order_by_chunks ) { - if ($piece =~ $seen_re) { - $restrict_aliases->{$alias} = 1; - } - } - - if ($non_prefetch_select_sql =~ $seen_re) { - $select_aliases->{$alias} = 1; - } - - if ($prefetch_select_sql =~ $seen_re) { - $prefetch_aliases->{$alias} = 1; - } - - } - } - - # Add any non-left joins to the restriction list (such joins are indeed restrictions) - for my $j (values %original_join_info) { - my $alias = $j->{-alias} or next; - $restrict_aliases->{$alias} = 1 if ( - (not $j->{-join_type}) - or - ($j->{-join_type} !~ /^left (?: \s+ outer)? $/xi) - ); - } - - # mark all join parents as mentioned - # (e.g. join => { cds => 'tracks' } - tracks will need to bring cds too ) - for my $collection ($restrict_aliases, $select_aliases) { - for my $alias (keys %$collection) { - $collection->{$_} = 1 - for (@{ $original_join_info{$alias}{-join_path} || [] }); - } - } - # construct the inner $from for the subquery - my %inner_joins = (map { %{$_ || {}} } ($restrict_aliases, $select_aliases) ); - 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) { + # we need to prune first, because this will determine if we need a group_by below + my $inner_from = $self->_prune_unused_joins ($from, $inner_select, $where, $inner_attrs); - # the dot comes from some weirdness in collapse - # remove after the rewrite - if ($attrs->{collapse}{".$alias"}) { - $inner_attrs->{group_by} ||= $inner_select; - last; - } - } - } - - # 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, @@ -177,7 +118,7 @@ sub _adjust_select_args_for_complex_prefetch { my $subq_joinspec = { -alias => $attrs->{alias}, - -source_handle => $inner_from[0]{-source_handle}, + -source_handle => $inner_from->[0]{-source_handle}, $attrs->{alias} => $subq, }; @@ -191,6 +132,11 @@ sub _adjust_select_args_for_complex_prefetch { # - 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) { @@ -206,6 +152,11 @@ sub _adjust_select_args_for_complex_prefetch { } } + # 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 @@ -213,27 +164,12 @@ sub _adjust_select_args_for_complex_prefetch { while (my $j = shift @$from) { my $alias = $j->[0]{-alias}; - if ($select_aliases->{$alias} || $prefetch_aliases->{$alias}) { + if ($outer_aliastypes->{select}{$alias}) { push @outer_from, $j; } - elsif ($restrict_aliases->{$alias}) { + elsif ($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}; } } @@ -250,6 +186,85 @@ sub _adjust_select_args_for_complex_prefetch { return (\@outer_from, $outer_select, $where, $outer_attrs); } +# Due to a lack of SQLA2 we fall back to crude scans of all the +# select/where/order/group attributes, in order to determine what +# aliases are neded to fulfill the query. This information is used +# throughout the code to prune unnecessary JOINs from the queries +# in an attempt to reduce the execution time. +# Although the method is pretty horrific, the worst thing that can +# 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_aliastypes_from_select_args { + my ( $self, $from, $select, $where, $attrs ) = @_; + + $self->throw_exception ('Unable to analyze custom {from}') + if ref $from ne 'ARRAY'; + + # what we will return + my $aliases_by_type; + + # see what aliases are there to work with + my $alias_list; + for (@$from) { + my $j = $_; + $j = $j->[0] if ref $j eq 'ARRAY'; + 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 + my $sql_maker = $self->sql_maker; + my $sep = quotemeta ($self->_sql_maker_opts->{name_sep} || '.'); + local $sql_maker->{quote_char}; # so that we can regex away + + + my $select_sql = $sql_maker->_recurse_fields ($select); + my $where_sql = $sql_maker->where ($where); + my $group_by_sql = $sql_maker->_order_by({ + map { $_ => $attrs->{$_} } qw/group_by having/ + }); + my @order_by_chunks = ($self->_parse_order_by ($attrs->{order_by}) ); + + # match every alias to the sql chunks above + for my $alias (keys %$alias_list) { + my $al_re = qr/\b $alias $sep/x; + + for my $piece ($where_sql, $group_by_sql) { + $aliases_by_type->{restrict}{$alias} = 1 if ($piece =~ $al_re); + } + + for my $piece ($select_sql, @order_by_chunks ) { + $aliases_by_type->{select}{$alias} = 1 if ($piece =~ $al_re); + } + } + + # Add any non-left joins to the restriction list (such joins are indeed restrictions) + for my $j (values %$alias_list) { + my $alias = $j->{-alias} or next; + $aliases_by_type->{restrict}{$alias} = 1 if ( + (not $j->{-join_type}) + or + ($j->{-join_type} !~ /^left (?: \s+ outer)? $/xi) + ); + } + + # mark all join parents as mentioned + # (e.g. join => { cds => 'tracks' } - tracks will need to bring cds too ) + for my $type (keys %$aliases_by_type) { + for my $alias (keys %{$aliases_by_type->{$type}}) { + $aliases_by_type->{$type}{$_} = 1 + for (map { keys %$_ } @{ $alias_list->{$alias}{-join_path} || [] }); + } + } + + return $aliases_by_type; +} + sub _resolve_ident_sources { my ($self, $ident) = @_; @@ -388,7 +403,7 @@ sub _straight_join_to_node { # anyway, and deep cloning is just too fucking expensive # So replace the first hashref in the node arrayref manually my @new_from = ($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}; @@ -441,13 +456,17 @@ sub _strip_cond_qualifiers { for (my $i = 0; $i < @cond; $i++) { my $entry = $cond[$i]; my $hash; - if (ref $entry eq 'HASH') { + my $ref = ref $entry; + if ($ref eq 'HASH' or $ref eq 'ARRAY') { $hash = $self->_strip_cond_qualifiers($entry); } - else { + elsif (! $ref) { $entry =~ /([^.]+)$/; $hash->{$1} = $cond[++$i]; } + else { + $self->throw_exception ("_strip_cond_qualifiers() is unable to handle a condition reftype $ref"); + } push @{$cond->{-and}}, $hash; } } @@ -465,5 +484,21 @@ sub _strip_cond_qualifiers { return $cond; } +sub _parse_order_by { + my ($self, $order_by) = @_; + + return scalar $self->sql_maker->_order_by_chunks ($order_by) + unless wantarray; + + my $sql_maker = $self->sql_maker; + local $sql_maker->{quote_char}; #disable quoting + my @chunks; + for my $chunk (map { ref $_ ? @$_ : $_ } ($sql_maker->_order_by_chunks ($order_by) ) ) { + $chunk =~ s/\s+ (?: ASC|DESC ) \s* $//ix; + push @chunks, $chunk; + } + + return @chunks; +} 1;