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 {
28 my ($from, $select, $where, $attrs) = @_;
30 if (ref $from ne 'ARRAY' || ref $from->[0] ne 'HASH' || ref $from->[1] ne 'ARRAY') {
31 return $from; # only standard {from} specs are supported
34 my $aliastypes = $self->_resolve_aliastypes_from_select_args(@_);
36 # a grouped set will not be affected by amount of rows. Thus any
37 # {multiplying} joins can go
38 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 for the subquery
105 # we need to prune first, because this will determine if we need a group_by below
106 my $inner_from = $self->_prune_unused_joins ($from, $inner_select, $where, $inner_attrs);
108 # if a multi-type join was needed in the subquery - add a group_by to simulate the
109 # collapse in the subq
110 $inner_attrs->{group_by} ||= $inner_select
111 if first { ! $_->[0]{-is_single} } (@{$inner_from}[1 .. $#$inner_from]);
113 # generate the subquery
114 my $subq = $self->_select_args_to_query (
121 my $subq_joinspec = {
122 -alias => $attrs->{alias},
123 -source_handle => $inner_from->[0]{-source_handle},
124 $attrs->{alias} => $subq,
127 # Generate the outer from - this is relatively easy (really just replace
128 # the join slot with the subquery), with a major caveat - we can not
129 # join anything that is non-selecting (not part of the prefetch), but at
130 # the same time is a multi-type relationship, as it will explode the result.
132 # There are two possibilities here
133 # - either the join is non-restricting, in which case we simply throw it away
134 # - it is part of the restrictions, in which case we need to collapse the outer
135 # result by tackling yet another group_by to the outside of the query
137 # normalize a copy of $from, so it will be easier to work with further
138 # down (i.e. promote the initial hashref to an AoH)
140 $from->[0] = [ $from->[0] ];
142 # so first generate the outer_from, up to the substitution point
144 while (my $j = shift @$from) {
145 if ($j->[0]{-alias} eq $attrs->{alias}) { # time to swap
150 last; # we'll take care of what's left in $from below
153 push @outer_from, $j;
157 # scan the from spec against different attributes, and see which joins are needed
159 my $outer_aliastypes =
160 $self->_resolve_aliastypes_from_select_args( $from, $outer_select, $where, $outer_attrs );
162 # see what's left - throw away if not selecting/restricting
163 # also throw in a group_by if restricting to guard against
164 # cross-join explosions
166 while (my $j = shift @$from) {
167 my $alias = $j->[0]{-alias};
169 if ($outer_aliastypes->{selecting}{$alias}) {
170 push @outer_from, $j;
172 elsif ($outer_aliastypes->{restricting}{$alias}) {
173 push @outer_from, $j;
174 $outer_attrs->{group_by} ||= $outer_select unless $j->[0]{-is_single};
178 # demote the outer_from head
179 $outer_from[0] = $outer_from[0][0];
181 # This is totally horrific - the $where ends up in both the inner and outer query
182 # Unfortunately not much can be done until SQLA2 introspection arrives, and even
183 # then if where conditions apply to the *right* side of the prefetch, you may have
184 # to both filter the inner select (e.g. to apply a limit) and then have to re-filter
185 # the outer select to exclude joins you didin't want in the first place
187 # OTOH it can be seen as a plus: <ash> (notes that this query would make a DBA cry ;)
188 return (\@outer_from, $outer_select, $where, $outer_attrs);
192 # I KNOW THIS SUCKS! GET SQLA2 OUT THE DOOR SO THIS CAN DIE!
194 # Due to a lack of SQLA2 we fall back to crude scans of all the
195 # select/where/order/group attributes, in order to determine what
196 # aliases are neded to fulfill the query. This information is used
197 # throughout the code to prune unnecessary JOINs from the queries
198 # in an attempt to reduce the execution time.
199 # Although the method is pretty horrific, the worst thing that can
200 # happen is for it to fail due to some scalar SQL, which in turn will
201 # result in a vocal exception.
202 sub _resolve_aliastypes_from_select_args {
203 my ( $self, $from, $select, $where, $attrs ) = @_;
205 $self->throw_exception ('Unable to analyze custom {from}')
206 if ref $from ne 'ARRAY';
208 # what we will return
211 # see what aliases are there to work with
215 $j = $j->[0] if ref $j eq 'ARRAY';
216 my $al = $j->{-alias}
219 $alias_list->{$al} = $j;
220 $aliases_by_type->{multiplying}{$al} = 1
221 unless $j->{-is_single};
224 # get a column to source/alias map (including unqualified ones)
225 my $colinfo = $self->_resolve_column_info ($from);
227 # set up a botched SQLA
228 my $sql_maker = $self->sql_maker;
230 local $sql_maker->{having_bind}; # these are throw away results
232 # we can't scan properly without any quoting (\b doesn't cut it
233 # everywhere), so unless there is proper quoting set - use our
234 # own weird impossible character.
235 # Also in the case of no quoting, we need to explicitly disable
236 # name_sep, otherwise sorry nasty legacy syntax like
237 # { 'count(foo.id)' => { '>' => 3 } } will stop working >:(
238 local $sql_maker->{quote_char} = $sql_maker->{quote_char};
239 local $sql_maker->{name_sep} = $sql_maker->{name_sep};
241 unless (defined $sql_maker->{quote_char} and length $sql_maker->{quote_char}) {
242 $sql_maker->{quote_char} = "\x00";
243 $sql_maker->{name_sep} = '';
246 my ($lquote, $rquote, $sep) = map { quotemeta $_ } ($sql_maker->_quote_chars, $sql_maker->name_sep);
248 # generate sql chunks
251 $sql_maker->_recurse_where ($where),
252 $sql_maker->_parse_rs_attrs ({
253 map { $_ => $attrs->{$_} } (qw/group_by having/)
257 $self->_extract_order_columns ($attrs->{order_by}, $sql_maker),
258 $sql_maker->_recurse_fields ($select),
262 # throw away empty chunks
263 $_ = [ map { $_ || () } @$_ ] for values %$to_scan;
265 # first loop through all fully qualified columns and get the corresponding
266 # alias (should work even if they are in scalarrefs)
267 for my $alias (keys %$alias_list) {
269 $lquote $alias $rquote $sep
274 for my $type (keys %$to_scan) {
275 for my $piece (@{$to_scan->{$type}}) {
276 $aliases_by_type->{$type}{$alias} = 1 if ($piece =~ $al_re);
281 # now loop through unqualified column names, and try to locate them within
283 for my $col (keys %$colinfo) {
284 next if $col =~ / \. /x; # if column is qualified it was caught by the above
286 my $col_re = qr/ $lquote $col $rquote /x;
288 for my $type (keys %$to_scan) {
289 for my $piece (@{$to_scan->{$type}}) {
290 $aliases_by_type->{$type}{$colinfo->{$col}{-source_alias}} = 1 if ($piece =~ $col_re);
295 # Add any non-left joins to the restriction list (such joins are indeed restrictions)
296 for my $j (values %$alias_list) {
297 my $alias = $j->{-alias} or next;
298 $aliases_by_type->{restricting}{$alias} = 1 if (
299 (not $j->{-join_type})
301 ($j->{-join_type} !~ /^left (?: \s+ outer)? $/xi)
305 # mark all join parents as mentioned
306 # (e.g. join => { cds => 'tracks' } - tracks will need to bring cds too )
307 for my $type (keys %$aliases_by_type) {
308 for my $alias (keys %{$aliases_by_type->{$type}}) {
309 $aliases_by_type->{$type}{$_} = 1
310 for (map { values %$_ } @{ $alias_list->{$alias}{-join_path} || [] });
314 return $aliases_by_type;
317 sub _resolve_ident_sources {
318 my ($self, $ident) = @_;
320 my $alias2source = {};
323 # the reason this is so contrived is that $ident may be a {from}
324 # structure, specifying multiple tables to join
325 if ( blessed $ident && $ident->isa("DBIx::Class::ResultSource") ) {
326 # this is compat mode for insert/update/delete which do not deal with aliases
327 $alias2source->{me} = $ident;
330 elsif (ref $ident eq 'ARRAY') {
334 if (ref $_ eq 'HASH') {
336 $rs_alias = $tabinfo->{-alias};
338 if (ref $_ eq 'ARRAY' and ref $_->[0] eq 'HASH') {
342 $alias2source->{$tabinfo->{-alias}} = $tabinfo->{-source_handle}->resolve
343 if ($tabinfo->{-source_handle});
347 return ($alias2source, $rs_alias);
350 # Takes $ident, \@column_names
352 # returns { $column_name => \%column_info, ... }
353 # also note: this adds -result_source => $rsrc to the column info
355 # If no columns_names are supplied returns info about *all* columns
357 sub _resolve_column_info {
358 my ($self, $ident, $colnames) = @_;
359 my ($alias2src, $root_alias) = $self->_resolve_ident_sources($ident);
361 my (%return, %seen_cols, @auto_colnames);
363 # compile a global list of column names, to be able to properly
364 # disambiguate unqualified column names (if at all possible)
365 for my $alias (keys %$alias2src) {
366 my $rsrc = $alias2src->{$alias};
367 for my $colname ($rsrc->columns) {
368 push @{$seen_cols{$colname}}, $alias;
369 push @auto_colnames, "$alias.$colname" unless $colnames;
375 grep { @{$seen_cols{$_}} == 1 } (keys %seen_cols),
379 foreach my $col (@$colnames) {
380 my ($alias, $colname) = $col =~ m/^ (?: ([^\.]+) \. )? (.+) $/x;
383 # see if the column was seen exactly once (so we know which rsrc it came from)
384 if ($seen_cols{$colname} and @{$seen_cols{$colname}} == 1) {
385 $alias = $seen_cols{$colname}[0];
392 my $rsrc = $alias2src->{$alias};
393 $return{$col} = $rsrc && {
394 %{$rsrc->column_info($colname)},
395 -result_source => $rsrc,
396 -source_alias => $alias,
403 # The DBIC relationship chaining implementation is pretty simple - every
404 # new related_relationship is pushed onto the {from} stack, and the {select}
405 # window simply slides further in. This means that when we count somewhere
406 # in the middle, we got to make sure that everything in the join chain is an
407 # actual inner join, otherwise the count will come back with unpredictable
408 # results (a resultset may be generated with _some_ rows regardless of if
409 # the relation which the $rs currently selects has rows or not). E.g.
410 # $artist_rs->cds->count - normally generates:
411 # SELECT COUNT( * ) FROM artist me LEFT JOIN cd cds ON cds.artist = me.artistid
412 # which actually returns the number of artists * (number of cds || 1)
414 # So what we do here is crawl {from}, determine if the current alias is at
415 # the top of the stack, and if not - make sure the chain is inner-joined down
418 sub _inner_join_to_node {
419 my ($self, $from, $alias) = @_;
421 # subqueries and other oddness are naturally not supported
427 ref $from->[0] ne 'HASH'
431 $from->[0]{-alias} eq $alias # this last bit means $alias is the head of $from - nothing to do
434 # find the current $alias in the $from structure
437 for my $j (@{$from}[1 .. $#$from]) {
438 if ($j->[0]{-alias} eq $alias) {
439 $switch_branch = $j->[0]{-join_path};
444 # something else went quite wrong
445 return $from unless $switch_branch;
447 # So it looks like we will have to switch some stuff around.
448 # local() is useless here as we will be leaving the scope
449 # anyway, and deep cloning is just too fucking expensive
450 # So replace the first hashref in the node arrayref manually
451 my @new_from = ($from->[0]);
452 my $sw_idx = { map { (values %$_), 1 } @$switch_branch }; #there's one k/v per join-path
454 for my $j (@{$from}[1 .. $#$from]) {
455 my $jalias = $j->[0]{-alias};
457 if ($sw_idx->{$jalias}) {
458 my %attrs = %{$j->[0]};
459 delete $attrs{-join_type};
473 # Most databases do not allow aliasing of tables in UPDATE/DELETE. Thus
474 # a condition containing 'me' or other table prefixes will not work
475 # at all. What this code tries to do (badly) is introspect the condition
476 # and remove all column qualifiers. If it bails out early (returns undef)
477 # the calling code should try another approach (e.g. a subquery)
478 sub _strip_cond_qualifiers {
479 my ($self, $where) = @_;
483 # No-op. No condition, we're updating/deleting everything
484 return $cond unless $where;
486 if (ref $where eq 'ARRAY') {
490 foreach my $key (keys %{$_}) {
492 $hash{$1} = $_->{$key};
498 elsif (ref $where eq 'HASH') {
499 if ( (keys %$where) == 1 && ( (keys %{$where})[0] eq '-and' )) {
501 my @cond = @{$where->{-and}};
502 for (my $i = 0; $i < @cond; $i++) {
503 my $entry = $cond[$i];
505 my $ref = ref $entry;
506 if ($ref eq 'HASH' or $ref eq 'ARRAY') {
507 $hash = $self->_strip_cond_qualifiers($entry);
510 $entry =~ /([^.]+)$/;
511 $hash->{$1} = $cond[++$i];
514 $self->throw_exception ("_strip_cond_qualifiers() is unable to handle a condition reftype $ref");
516 push @{$cond->{-and}}, $hash;
520 foreach my $key (keys %$where) {
522 $cond->{$1} = $where->{$key};
533 sub _extract_order_columns {
534 my ($self, $order_by, $sql_maker) = @_;
537 my ($sql_maker, $order_by) = @_;
539 return scalar $sql_maker->_order_by_chunks ($order_by)
543 for my $chunk (map { ref $_ ? @$_ : $_ } ($sql_maker->_order_by_chunks ($order_by) ) ) {
544 $chunk =~ s/\s+ (?: ASC|DESC ) \s* $//ix;
545 push @chunks, $chunk;
552 return $parser->($sql_maker, $order_by);
555 $sql_maker = $self->sql_maker;
556 local $sql_maker->{quote_char};
557 return $parser->($sql_maker, $order_by);