1 package #hide from PAUSE
2 DBIx::Class::Storage::DBIHacks;
5 # This module contains code that should never have seen the light of day,
6 # does not belong in the Storage, or is otherwise unfit for public
7 # display. The arrival of SQLA2 should immediately oboslete 90% of this
13 use base 'DBIx::Class::Storage';
16 use Carp::Clan qw/^DBIx::Class/;
17 use List::Util 'first';
18 use Scalar::Util 'blessed';
22 # This code will remove non-selecting/non-restricting joins from
23 # {from} specs, aiding the RDBMS query optimizer
25 sub _prune_unused_joins {
27 my ($from, $select, $where, $attrs) = @_;
29 return $from unless $self->_use_join_optimizer;
31 if (ref $from ne 'ARRAY' || ref $from->[0] ne 'HASH' || ref $from->[1] ne 'ARRAY') {
32 return $from; # only standard {from} specs are supported
35 my $aliastypes = $self->_resolve_aliastypes_from_select_args(@_);
37 # a grouped set will not be affected by amount of rows. Thus any
38 # {multiplying} joins can go
39 delete $aliastypes->{multiplying} if $attrs->{group_by};
41 my @newfrom = $from->[0]; # FROM head is always present
43 my %need_joins = (map { %{$_||{}} } (values %$aliastypes) );
44 for my $j (@{$from}[1..$#$from]) {
45 push @newfrom, $j if (
46 (! $j->[0]{-alias}) # legacy crap
48 $need_joins{$j->[0]{-alias}}
56 # This is the code producing joined subqueries like:
57 # SELECT me.*, other.* FROM ( SELECT me.* FROM ... ) JOIN other ON ...
59 sub _adjust_select_args_for_complex_prefetch {
60 my ($self, $from, $select, $where, $attrs) = @_;
62 $self->throw_exception ('Nothing to prefetch... how did we get here?!')
63 if not @{$attrs->{_prefetch_select}};
65 $self->throw_exception ('Complex prefetches are not supported on resultsets with a custom from attribute')
66 if (ref $from ne 'ARRAY' || ref $from->[0] ne 'HASH' || ref $from->[1] ne 'ARRAY');
69 # generate inner/outer attribute lists, remove stuff that doesn't apply
70 my $outer_attrs = { %$attrs };
71 delete $outer_attrs->{$_} for qw/where bind rows offset group_by having/;
73 my $inner_attrs = { %$attrs };
74 delete $inner_attrs->{$_} for qw/for collapse _prefetch_select _collapse_order_by select as/;
77 # bring over all non-collapse-induced order_by into the inner query (if any)
78 # the outer one will have to keep them all
79 delete $inner_attrs->{order_by};
80 if (my $ord_cnt = @{$outer_attrs->{order_by}} - @{$outer_attrs->{_collapse_order_by}} ) {
81 $inner_attrs->{order_by} = [
82 @{$outer_attrs->{order_by}}[ 0 .. $ord_cnt - 1]
86 # generate the inner/outer select lists
87 # for inside we consider only stuff *not* brought in by the prefetch
88 # on the outside we substitute any function for its alias
89 my $outer_select = [ @$select ];
90 my $inner_select = [];
91 for my $i (0 .. ( @$outer_select - @{$outer_attrs->{_prefetch_select}} - 1) ) {
92 my $sel = $outer_select->[$i];
94 if (ref $sel eq 'HASH' ) {
95 $sel->{-as} ||= $attrs->{as}[$i];
96 $outer_select->[$i] = join ('.', $attrs->{alias}, ($sel->{-as} || "inner_column_$i") );
99 push @$inner_select, $sel;
101 push @{$inner_attrs->{as}}, $attrs->{as}[$i];
104 # construct the inner $from and lock it in a subquery
105 # we need to prune first, because this will determine if we need a group_by below
106 # the fake group_by is so that the pruner throws away all non-selecting, non-restricting
107 # multijoins (since we def. do not care about those inside the subquery)
109 my $subq_joinspec = do {
111 # must use it here regardless of user requests
112 local $self->{_use_join_optimizer} = 1;
114 my $inner_from = $self->_prune_unused_joins ($from, $inner_select, $where, {
115 group_by => ['dummy'], %$inner_attrs,
118 # if a multi-type join was needed in the subquery - add a group_by to simulate the
119 # collapse in the subq
121 ! $inner_attrs->{group_by}
123 first { ! $_->[0]{-is_single} } (@{$inner_from}[1 .. $#$inner_from])
125 $inner_attrs->{group_by} = $self->_group_over_selection (
126 $inner_from, $inner_select, $inner_attrs->{order_by}
130 # we already optimized $inner_from above
131 local $self->{_use_join_optimizer} = 0;
133 # generate the subquery
134 my $subq = $self->_select_args_to_query (
142 -alias => $attrs->{alias},
143 -source_handle => $inner_from->[0]{-source_handle},
144 $attrs->{alias} => $subq,
148 # Generate the outer from - this is relatively easy (really just replace
149 # the join slot with the subquery), with a major caveat - we can not
150 # join anything that is non-selecting (not part of the prefetch), but at
151 # the same time is a multi-type relationship, as it will explode the result.
153 # There are two possibilities here
154 # - either the join is non-restricting, in which case we simply throw it away
155 # - it is part of the restrictions, in which case we need to collapse the outer
156 # result by tackling yet another group_by to the outside of the query
160 # so first generate the outer_from, up to the substitution point
162 while (my $j = shift @$from) {
163 $j = [ $j ] unless ref $j eq 'ARRAY'; # promote the head-from to an AoH
165 if ($j->[0]{-alias} eq $attrs->{alias}) { # time to swap
170 last; # we'll take care of what's left in $from below
173 push @outer_from, $j;
177 # scan the *remaining* from spec against different attributes, and see which joins are needed
179 my $outer_aliastypes =
180 $self->_resolve_aliastypes_from_select_args( $from, $outer_select, $where, $outer_attrs );
182 # see what's left - throw away if not selecting/restricting
183 # also throw in a group_by if restricting to guard against
184 # cross-join explosions
186 while (my $j = shift @$from) {
187 my $alias = $j->[0]{-alias};
189 if ($outer_aliastypes->{selecting}{$alias}) {
190 push @outer_from, $j;
192 elsif ($outer_aliastypes->{restricting}{$alias}) {
193 push @outer_from, $j;
194 $outer_attrs->{group_by} ||= $outer_select unless $j->[0]{-is_single};
198 # demote the outer_from head
199 $outer_from[0] = $outer_from[0][0];
201 # This is totally horrific - the $where ends up in both the inner and outer query
202 # Unfortunately not much can be done until SQLA2 introspection arrives, and even
203 # then if where conditions apply to the *right* side of the prefetch, you may have
204 # to both filter the inner select (e.g. to apply a limit) and then have to re-filter
205 # the outer select to exclude joins you didin't want in the first place
207 # OTOH it can be seen as a plus: <ash> (notes that this query would make a DBA cry ;)
208 return (\@outer_from, $outer_select, $where, $outer_attrs);
212 # I KNOW THIS SUCKS! GET SQLA2 OUT THE DOOR SO THIS CAN DIE!
214 # Due to a lack of SQLA2 we fall back to crude scans of all the
215 # select/where/order/group attributes, in order to determine what
216 # aliases are neded to fulfill the query. This information is used
217 # throughout the code to prune unnecessary JOINs from the queries
218 # in an attempt to reduce the execution time.
219 # Although the method is pretty horrific, the worst thing that can
220 # happen is for it to fail due to some scalar SQL, which in turn will
221 # result in a vocal exception.
222 sub _resolve_aliastypes_from_select_args {
223 my ( $self, $from, $select, $where, $attrs ) = @_;
225 $self->throw_exception ('Unable to analyze custom {from}')
226 if ref $from ne 'ARRAY';
228 # what we will return
231 # see what aliases are there to work with
235 $j = $j->[0] if ref $j eq 'ARRAY';
236 my $al = $j->{-alias}
239 $alias_list->{$al} = $j;
240 $aliases_by_type->{multiplying}{$al} = 1
241 if ref($_) eq 'ARRAY' and ! $j->{-is_single}; # not array == {from} head == can't be multiplying
244 # get a column to source/alias map (including unqualified ones)
245 my $colinfo = $self->_resolve_column_info ($from);
247 # set up a botched SQLA
248 my $sql_maker = $self->sql_maker;
250 local $sql_maker->{having_bind}; # these are throw away results
252 # we can't scan properly without any quoting (\b doesn't cut it
253 # everywhere), so unless there is proper quoting set - use our
254 # own weird impossible character.
255 # Also in the case of no quoting, we need to explicitly disable
256 # name_sep, otherwise sorry nasty legacy syntax like
257 # { 'count(foo.id)' => { '>' => 3 } } will stop working >:(
258 local $sql_maker->{quote_char} = $sql_maker->{quote_char};
259 local $sql_maker->{name_sep} = $sql_maker->{name_sep};
261 unless (defined $sql_maker->{quote_char} and length $sql_maker->{quote_char}) {
262 $sql_maker->{quote_char} = ["\x00", "\xFF"];
263 # if we don't unset it we screw up retarded but unfortunately working
264 # 'MAX(foo.bar)' => { '>', 3 }
265 $sql_maker->{name_sep} = '';
268 my ($lquote, $rquote, $sep) = map { quotemeta $_ } ($sql_maker->_quote_chars, $sql_maker->name_sep);
270 # generate sql chunks
273 $sql_maker->_recurse_where ($where),
274 $sql_maker->_parse_rs_attrs ({
275 map { $_ => $attrs->{$_} } (qw/group_by having/)
279 $sql_maker->_recurse_fields ($select),
280 ( map { $_->[0] } $self->_extract_order_criteria ($attrs->{order_by}, $sql_maker) ),
284 # throw away empty chunks
285 $_ = [ map { $_ || () } @$_ ] for values %$to_scan;
287 # first loop through all fully qualified columns and get the corresponding
288 # alias (should work even if they are in scalarrefs)
289 for my $alias (keys %$alias_list) {
291 $lquote $alias $rquote $sep
296 for my $type (keys %$to_scan) {
297 for my $piece (@{$to_scan->{$type}}) {
298 $aliases_by_type->{$type}{$alias} = 1 if ($piece =~ $al_re);
303 # now loop through unqualified column names, and try to locate them within
305 for my $col (keys %$colinfo) {
306 next if $col =~ / \. /x; # if column is qualified it was caught by the above
308 my $col_re = qr/ $lquote $col $rquote /x;
310 for my $type (keys %$to_scan) {
311 for my $piece (@{$to_scan->{$type}}) {
312 $aliases_by_type->{$type}{$colinfo->{$col}{-source_alias}} = 1 if ($piece =~ $col_re);
317 # Add any non-left joins to the restriction list (such joins are indeed restrictions)
318 for my $j (values %$alias_list) {
319 my $alias = $j->{-alias} or next;
320 $aliases_by_type->{restricting}{$alias} = 1 if (
321 (not $j->{-join_type})
323 ($j->{-join_type} !~ /^left (?: \s+ outer)? $/xi)
327 # mark all restricting/selecting join parents as such
328 # (e.g. join => { cds => 'tracks' } - tracks will need to bring cds too )
329 for my $type (qw/restricting selecting/) {
330 for my $alias (keys %{$aliases_by_type->{$type}||{}}) {
331 $aliases_by_type->{$type}{$_} = 1
332 for (map { values %$_ } @{ $alias_list->{$alias}{-join_path} || [] });
336 return $aliases_by_type;
339 # This is the engine behind { distinct => 1 }
340 sub _group_over_selection {
341 my ($self, $from, $select, $order_by) = @_;
343 my $rs_column_list = $self->_resolve_column_info ($from);
345 my (@group_by, %group_index);
348 if (! ref($_) or ref ($_) ne 'HASH' ) {
351 if ($rs_column_list->{$_} and $_ !~ /\./ ) {
352 # add a fully qualified version as well
353 $group_index{"$rs_column_list->{$_}{-source_alias}.$_"}++;
358 # add any order_by parts that are not already present in the group_by
359 # we need to be careful not to add any named functions/aggregates
360 # i.e. order_by => [ ... { count => 'foo' } ... ]
361 for ($self->_extract_order_criteria($order_by)) {
362 # only consider real columns (for functions the user got to do an explicit group_by)
365 my $colinfo = $rs_column_list->{$chunk} or next;
367 $chunk = "$colinfo->{-source_alias}.$chunk" if $chunk !~ /\./;
368 push @group_by, $chunk unless $group_index{$chunk}++;
374 sub _resolve_ident_sources {
375 my ($self, $ident) = @_;
377 my $alias2source = {};
380 # the reason this is so contrived is that $ident may be a {from}
381 # structure, specifying multiple tables to join
382 if ( blessed $ident && $ident->isa("DBIx::Class::ResultSource") ) {
383 # this is compat mode for insert/update/delete which do not deal with aliases
384 $alias2source->{me} = $ident;
387 elsif (ref $ident eq 'ARRAY') {
391 if (ref $_ eq 'HASH') {
393 $rs_alias = $tabinfo->{-alias};
395 if (ref $_ eq 'ARRAY' and ref $_->[0] eq 'HASH') {
399 $alias2source->{$tabinfo->{-alias}} = $tabinfo->{-source_handle}->resolve
400 if ($tabinfo->{-source_handle});
404 return ($alias2source, $rs_alias);
407 # Takes $ident, \@column_names
409 # returns { $column_name => \%column_info, ... }
410 # also note: this adds -result_source => $rsrc to the column info
412 # If no columns_names are supplied returns info about *all* columns
414 sub _resolve_column_info {
415 my ($self, $ident, $colnames) = @_;
416 my ($alias2src, $root_alias) = $self->_resolve_ident_sources($ident);
418 my (%seen_cols, @auto_colnames);
420 # compile a global list of column names, to be able to properly
421 # disambiguate unqualified column names (if at all possible)
422 for my $alias (keys %$alias2src) {
423 my $rsrc = $alias2src->{$alias};
424 for my $colname ($rsrc->columns) {
425 push @{$seen_cols{$colname}}, $alias;
426 push @auto_colnames, "$alias.$colname" unless $colnames;
432 grep { @{$seen_cols{$_}} == 1 } (keys %seen_cols),
435 my (%return, $colinfos);
436 foreach my $col (@$colnames) {
437 my ($source_alias, $colname) = $col =~ m/^ (?: ([^\.]+) \. )? (.+) $/x;
439 # if the column was seen exactly once - we know which rsrc it came from
440 $source_alias ||= $seen_cols{$colname}[0]
441 if ($seen_cols{$colname} and @{$seen_cols{$colname}} == 1);
443 next unless $source_alias;
445 my $rsrc = $alias2src->{$source_alias}
449 %{ ( $colinfos->{$source_alias} ||= $rsrc->columns_info )->{$colname} },
450 -result_source => $rsrc,
451 -source_alias => $source_alias,
458 # The DBIC relationship chaining implementation is pretty simple - every
459 # new related_relationship is pushed onto the {from} stack, and the {select}
460 # window simply slides further in. This means that when we count somewhere
461 # in the middle, we got to make sure that everything in the join chain is an
462 # actual inner join, otherwise the count will come back with unpredictable
463 # results (a resultset may be generated with _some_ rows regardless of if
464 # the relation which the $rs currently selects has rows or not). E.g.
465 # $artist_rs->cds->count - normally generates:
466 # SELECT COUNT( * ) FROM artist me LEFT JOIN cd cds ON cds.artist = me.artistid
467 # which actually returns the number of artists * (number of cds || 1)
469 # So what we do here is crawl {from}, determine if the current alias is at
470 # the top of the stack, and if not - make sure the chain is inner-joined down
473 sub _inner_join_to_node {
474 my ($self, $from, $alias) = @_;
476 # subqueries and other oddness are naturally not supported
482 ref $from->[0] ne 'HASH'
486 $from->[0]{-alias} eq $alias # this last bit means $alias is the head of $from - nothing to do
489 # find the current $alias in the $from structure
492 for my $j (@{$from}[1 .. $#$from]) {
493 if ($j->[0]{-alias} eq $alias) {
494 $switch_branch = $j->[0]{-join_path};
499 # something else went quite wrong
500 return $from unless $switch_branch;
502 # So it looks like we will have to switch some stuff around.
503 # local() is useless here as we will be leaving the scope
504 # anyway, and deep cloning is just too fucking expensive
505 # So replace the first hashref in the node arrayref manually
506 my @new_from = ($from->[0]);
507 my $sw_idx = { map { (values %$_), 1 } @$switch_branch }; #there's one k/v per join-path
509 for my $j (@{$from}[1 .. $#$from]) {
510 my $jalias = $j->[0]{-alias};
512 if ($sw_idx->{$jalias}) {
513 my %attrs = %{$j->[0]};
514 delete $attrs{-join_type};
528 # Most databases do not allow aliasing of tables in UPDATE/DELETE. Thus
529 # a condition containing 'me' or other table prefixes will not work
530 # at all. What this code tries to do (badly) is introspect the condition
531 # and remove all column qualifiers. If it bails out early (returns undef)
532 # the calling code should try another approach (e.g. a subquery)
533 sub _strip_cond_qualifiers {
534 my ($self, $where) = @_;
538 # No-op. No condition, we're updating/deleting everything
539 return $cond unless $where;
541 if (ref $where eq 'ARRAY') {
545 foreach my $key (keys %{$_}) {
547 $hash{$1} = $_->{$key};
553 elsif (ref $where eq 'HASH') {
554 if ( (keys %$where) == 1 && ( (keys %{$where})[0] eq '-and' )) {
556 my @cond = @{$where->{-and}};
557 for (my $i = 0; $i < @cond; $i++) {
558 my $entry = $cond[$i];
560 my $ref = ref $entry;
561 if ($ref eq 'HASH' or $ref eq 'ARRAY') {
562 $hash = $self->_strip_cond_qualifiers($entry);
565 $entry =~ /([^.]+)$/;
566 $hash->{$1} = $cond[++$i];
569 $self->throw_exception ("_strip_cond_qualifiers() is unable to handle a condition reftype $ref");
571 push @{$cond->{-and}}, $hash;
575 foreach my $key (keys %$where) {
576 if ($key eq '-or' && ref $where->{$key} eq 'ARRAY') {
577 $cond->{$key} = $self->_strip_cond_qualifiers($where->{$key});
581 $cond->{$1} = $where->{$key};
593 sub _extract_order_criteria {
594 my ($self, $order_by, $sql_maker) = @_;
597 my ($sql_maker, $order_by) = @_;
599 return scalar $sql_maker->_order_by_chunks ($order_by)
603 for ($sql_maker->_order_by_chunks ($order_by) ) {
604 my $chunk = ref $_ ? $_ : [ $_ ];
605 $chunk->[0] =~ s/\s+ (?: ASC|DESC ) \s* $//ix;
606 push @chunks, $chunk;
613 return $parser->($sql_maker, $order_by);
616 $sql_maker = $self->sql_maker;
617 local $sql_maker->{quote_char};
618 return $parser->($sql_maker, $order_by);