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
120 $inner_attrs->{group_by} ||= $inner_select
121 if first { ! $_->[0]{-is_single} } (@{$inner_from}[1 .. $#$inner_from]);
123 # we already optimized $inner_from above
124 local $self->{_use_join_optimizer} = 0;
126 # generate the subquery
127 my $subq = $self->_select_args_to_query (
135 -alias => $attrs->{alias},
136 -source_handle => $inner_from->[0]{-source_handle},
137 $attrs->{alias} => $subq,
141 # Generate the outer from - this is relatively easy (really just replace
142 # the join slot with the subquery), with a major caveat - we can not
143 # join anything that is non-selecting (not part of the prefetch), but at
144 # the same time is a multi-type relationship, as it will explode the result.
146 # There are two possibilities here
147 # - either the join is non-restricting, in which case we simply throw it away
148 # - it is part of the restrictions, in which case we need to collapse the outer
149 # result by tackling yet another group_by to the outside of the query
153 # so first generate the outer_from, up to the substitution point
155 while (my $j = shift @$from) {
156 $j = [ $j ] unless ref $j eq 'ARRAY'; # promote the head-from to an AoH
158 if ($j->[0]{-alias} eq $attrs->{alias}) { # time to swap
163 last; # we'll take care of what's left in $from below
166 push @outer_from, $j;
170 # scan the *remaining* from spec against different attributes, and see which joins are needed
172 my $outer_aliastypes =
173 $self->_resolve_aliastypes_from_select_args( $from, $outer_select, $where, $outer_attrs );
175 # see what's left - throw away if not selecting/restricting
176 # also throw in a group_by if restricting to guard against
177 # cross-join explosions
179 while (my $j = shift @$from) {
180 my $alias = $j->[0]{-alias};
182 if ($outer_aliastypes->{selecting}{$alias}) {
183 push @outer_from, $j;
185 elsif ($outer_aliastypes->{restricting}{$alias}) {
186 push @outer_from, $j;
187 $outer_attrs->{group_by} ||= $outer_select unless $j->[0]{-is_single};
191 # demote the outer_from head
192 $outer_from[0] = $outer_from[0][0];
194 # This is totally horrific - the $where ends up in both the inner and outer query
195 # Unfortunately not much can be done until SQLA2 introspection arrives, and even
196 # then if where conditions apply to the *right* side of the prefetch, you may have
197 # to both filter the inner select (e.g. to apply a limit) and then have to re-filter
198 # the outer select to exclude joins you didin't want in the first place
200 # OTOH it can be seen as a plus: <ash> (notes that this query would make a DBA cry ;)
201 return (\@outer_from, $outer_select, $where, $outer_attrs);
205 # I KNOW THIS SUCKS! GET SQLA2 OUT THE DOOR SO THIS CAN DIE!
207 # Due to a lack of SQLA2 we fall back to crude scans of all the
208 # select/where/order/group attributes, in order to determine what
209 # aliases are neded to fulfill the query. This information is used
210 # throughout the code to prune unnecessary JOINs from the queries
211 # in an attempt to reduce the execution time.
212 # Although the method is pretty horrific, the worst thing that can
213 # happen is for it to fail due to some scalar SQL, which in turn will
214 # result in a vocal exception.
215 sub _resolve_aliastypes_from_select_args {
216 my ( $self, $from, $select, $where, $attrs ) = @_;
218 $self->throw_exception ('Unable to analyze custom {from}')
219 if ref $from ne 'ARRAY';
221 # what we will return
224 # see what aliases are there to work with
228 $j = $j->[0] if ref $j eq 'ARRAY';
229 my $al = $j->{-alias}
232 $alias_list->{$al} = $j;
233 $aliases_by_type->{multiplying}{$al} = 1
234 if ref($_) eq 'ARRAY' and ! $j->{-is_single}; # not array == {from} head == can't be multiplying
237 # get a column to source/alias map (including unqualified ones)
238 my $colinfo = $self->_resolve_column_info ($from);
240 # set up a botched SQLA
241 my $sql_maker = $self->sql_maker;
243 local $sql_maker->{having_bind}; # these are throw away results
245 # we can't scan properly without any quoting (\b doesn't cut it
246 # everywhere), so unless there is proper quoting set - use our
247 # own weird impossible character.
248 # Also in the case of no quoting, we need to explicitly disable
249 # name_sep, otherwise sorry nasty legacy syntax like
250 # { 'count(foo.id)' => { '>' => 3 } } will stop working >:(
251 local $sql_maker->{quote_char} = $sql_maker->{quote_char};
252 local $sql_maker->{name_sep} = $sql_maker->{name_sep};
254 unless (defined $sql_maker->{quote_char} and length $sql_maker->{quote_char}) {
255 $sql_maker->{quote_char} = "\x00";
256 $sql_maker->{name_sep} = '';
259 my ($lquote, $rquote, $sep) = map { quotemeta $_ } ($sql_maker->_quote_chars, $sql_maker->name_sep);
261 # generate sql chunks
264 $sql_maker->_recurse_where ($where),
265 $sql_maker->_parse_rs_attrs ({
266 map { $_ => $attrs->{$_} } (qw/group_by having/)
270 $self->_extract_order_columns ($attrs->{order_by}, $sql_maker),
271 $sql_maker->_recurse_fields ($select),
275 # throw away empty chunks
276 $_ = [ map { $_ || () } @$_ ] for values %$to_scan;
278 # first loop through all fully qualified columns and get the corresponding
279 # alias (should work even if they are in scalarrefs)
280 for my $alias (keys %$alias_list) {
282 $lquote $alias $rquote $sep
287 for my $type (keys %$to_scan) {
288 for my $piece (@{$to_scan->{$type}}) {
289 $aliases_by_type->{$type}{$alias} = 1 if ($piece =~ $al_re);
294 # now loop through unqualified column names, and try to locate them within
296 for my $col (keys %$colinfo) {
297 next if $col =~ / \. /x; # if column is qualified it was caught by the above
299 my $col_re = qr/ $lquote $col $rquote /x;
301 for my $type (keys %$to_scan) {
302 for my $piece (@{$to_scan->{$type}}) {
303 $aliases_by_type->{$type}{$colinfo->{$col}{-source_alias}} = 1 if ($piece =~ $col_re);
308 # Add any non-left joins to the restriction list (such joins are indeed restrictions)
309 for my $j (values %$alias_list) {
310 my $alias = $j->{-alias} or next;
311 $aliases_by_type->{restricting}{$alias} = 1 if (
312 (not $j->{-join_type})
314 ($j->{-join_type} !~ /^left (?: \s+ outer)? $/xi)
318 # mark all restricting/selecting join parents as such
319 # (e.g. join => { cds => 'tracks' } - tracks will need to bring cds too )
320 for my $type (qw/restricting selecting/) {
321 for my $alias (keys %{$aliases_by_type->{$type}||{}}) {
322 $aliases_by_type->{$type}{$_} = 1
323 for (map { values %$_ } @{ $alias_list->{$alias}{-join_path} || [] });
327 return $aliases_by_type;
330 sub _resolve_ident_sources {
331 my ($self, $ident) = @_;
333 my $alias2source = {};
336 # the reason this is so contrived is that $ident may be a {from}
337 # structure, specifying multiple tables to join
338 if ( blessed $ident && $ident->isa("DBIx::Class::ResultSource") ) {
339 # this is compat mode for insert/update/delete which do not deal with aliases
340 $alias2source->{me} = $ident;
343 elsif (ref $ident eq 'ARRAY') {
347 if (ref $_ eq 'HASH') {
349 $rs_alias = $tabinfo->{-alias};
351 if (ref $_ eq 'ARRAY' and ref $_->[0] eq 'HASH') {
355 $alias2source->{$tabinfo->{-alias}} = $tabinfo->{-source_handle}->resolve
356 if ($tabinfo->{-source_handle});
360 return ($alias2source, $rs_alias);
363 # Takes $ident, \@column_names
365 # returns { $column_name => \%column_info, ... }
366 # also note: this adds -result_source => $rsrc to the column info
368 # If no columns_names are supplied returns info about *all* columns
370 sub _resolve_column_info {
371 my ($self, $ident, $colnames) = @_;
372 my ($alias2src, $root_alias) = $self->_resolve_ident_sources($ident);
374 my (%return, %seen_cols, @auto_colnames);
376 # compile a global list of column names, to be able to properly
377 # disambiguate unqualified column names (if at all possible)
378 for my $alias (keys %$alias2src) {
379 my $rsrc = $alias2src->{$alias};
380 for my $colname ($rsrc->columns) {
381 push @{$seen_cols{$colname}}, $alias;
382 push @auto_colnames, "$alias.$colname" unless $colnames;
388 grep { @{$seen_cols{$_}} == 1 } (keys %seen_cols),
392 foreach my $col (@$colnames) {
393 my ($alias, $colname) = $col =~ m/^ (?: ([^\.]+) \. )? (.+) $/x;
396 # see if the column was seen exactly once (so we know which rsrc it came from)
397 if ($seen_cols{$colname} and @{$seen_cols{$colname}} == 1) {
398 $alias = $seen_cols{$colname}[0];
405 my $rsrc = $alias2src->{$alias};
406 $return{$col} = $rsrc && {
407 %{$rsrc->column_info($colname)},
408 -result_source => $rsrc,
409 -source_alias => $alias,
416 # The DBIC relationship chaining implementation is pretty simple - every
417 # new related_relationship is pushed onto the {from} stack, and the {select}
418 # window simply slides further in. This means that when we count somewhere
419 # in the middle, we got to make sure that everything in the join chain is an
420 # actual inner join, otherwise the count will come back with unpredictable
421 # results (a resultset may be generated with _some_ rows regardless of if
422 # the relation which the $rs currently selects has rows or not). E.g.
423 # $artist_rs->cds->count - normally generates:
424 # SELECT COUNT( * ) FROM artist me LEFT JOIN cd cds ON cds.artist = me.artistid
425 # which actually returns the number of artists * (number of cds || 1)
427 # So what we do here is crawl {from}, determine if the current alias is at
428 # the top of the stack, and if not - make sure the chain is inner-joined down
431 sub _inner_join_to_node {
432 my ($self, $from, $alias) = @_;
434 # subqueries and other oddness are naturally not supported
440 ref $from->[0] ne 'HASH'
444 $from->[0]{-alias} eq $alias # this last bit means $alias is the head of $from - nothing to do
447 # find the current $alias in the $from structure
450 for my $j (@{$from}[1 .. $#$from]) {
451 if ($j->[0]{-alias} eq $alias) {
452 $switch_branch = $j->[0]{-join_path};
457 # something else went quite wrong
458 return $from unless $switch_branch;
460 # So it looks like we will have to switch some stuff around.
461 # local() is useless here as we will be leaving the scope
462 # anyway, and deep cloning is just too fucking expensive
463 # So replace the first hashref in the node arrayref manually
464 my @new_from = ($from->[0]);
465 my $sw_idx = { map { (values %$_), 1 } @$switch_branch }; #there's one k/v per join-path
467 for my $j (@{$from}[1 .. $#$from]) {
468 my $jalias = $j->[0]{-alias};
470 if ($sw_idx->{$jalias}) {
471 my %attrs = %{$j->[0]};
472 delete $attrs{-join_type};
486 # Most databases do not allow aliasing of tables in UPDATE/DELETE. Thus
487 # a condition containing 'me' or other table prefixes will not work
488 # at all. What this code tries to do (badly) is introspect the condition
489 # and remove all column qualifiers. If it bails out early (returns undef)
490 # the calling code should try another approach (e.g. a subquery)
491 sub _strip_cond_qualifiers {
492 my ($self, $where) = @_;
496 # No-op. No condition, we're updating/deleting everything
497 return $cond unless $where;
499 if (ref $where eq 'ARRAY') {
503 foreach my $key (keys %{$_}) {
505 $hash{$1} = $_->{$key};
511 elsif (ref $where eq 'HASH') {
512 if ( (keys %$where) == 1 && ( (keys %{$where})[0] eq '-and' )) {
514 my @cond = @{$where->{-and}};
515 for (my $i = 0; $i < @cond; $i++) {
516 my $entry = $cond[$i];
518 my $ref = ref $entry;
519 if ($ref eq 'HASH' or $ref eq 'ARRAY') {
520 $hash = $self->_strip_cond_qualifiers($entry);
523 $entry =~ /([^.]+)$/;
524 $hash->{$1} = $cond[++$i];
527 $self->throw_exception ("_strip_cond_qualifiers() is unable to handle a condition reftype $ref");
529 push @{$cond->{-and}}, $hash;
533 foreach my $key (keys %$where) {
534 if ($key eq '-or' && ref $where->{$key} eq 'ARRAY') {
535 $cond->{$key} = $self->_strip_cond_qualifiers($where->{$key});
539 $cond->{$1} = $where->{$key};
551 sub _extract_order_columns {
552 my ($self, $order_by, $sql_maker) = @_;
555 my ($sql_maker, $order_by) = @_;
557 return scalar $sql_maker->_order_by_chunks ($order_by)
561 for my $chunk (map { ref $_ ? @$_ : $_ } ($sql_maker->_order_by_chunks ($order_by) ) ) {
562 $chunk =~ s/\s+ (?: ASC|DESC ) \s* $//ix;
563 push @chunks, $chunk;
570 return $parser->($sql_maker, $order_by);
573 $sql_maker = $self->sql_maker;
574 local $sql_maker->{quote_char};
575 return $parser->($sql_maker, $order_by);