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1 | package DBIx::Class::SQLMaker::LimitDialects; |
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2 | |
3 | use warnings; |
4 | use strict; |
5 | |
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6 | use List::Util 'first'; |
7 | use namespace::clean; |
8 | |
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9 | # constants are used not only here, but also in comparison tests |
10 | sub __rows_bindtype () { |
11 | +{ sqlt_datatype => 'integer' } |
12 | } |
13 | sub __offset_bindtype () { |
14 | +{ sqlt_datatype => 'integer' } |
15 | } |
16 | sub __total_bindtype () { |
17 | +{ sqlt_datatype => 'integer' } |
18 | } |
19 | |
d5dedbd6 |
20 | =head1 NAME |
21 | |
22 | DBIx::Class::SQLMaker::LimitDialects - SQL::Abstract::Limit-like functionality for DBIx::Class::SQLMaker |
23 | |
24 | =head1 DESCRIPTION |
25 | |
26 | This module replicates a lot of the functionality originally found in |
27 | L<SQL::Abstract::Limit>. While simple limits would work as-is, the more |
28 | complex dialects that require e.g. subqueries could not be reliably |
29 | implemented without taking full advantage of the metadata locked within |
30 | L<DBIx::Class::ResultSource> classes. After reimplementation of close to |
31 | 80% of the L<SQL::Abstract::Limit> functionality it was deemed more |
32 | practical to simply make an independent DBIx::Class-specific limit-dialect |
33 | provider. |
34 | |
35 | =head1 SQL LIMIT DIALECTS |
36 | |
37 | Note that the actual implementations listed below never use C<*> literally. |
38 | Instead proper re-aliasing of selectors and order criteria is done, so that |
39 | the limit dialect are safe to use on joined resultsets with clashing column |
40 | names. |
41 | |
42 | Currently the provided dialects are: |
43 | |
d5dedbd6 |
44 | =head2 LimitOffset |
45 | |
46 | SELECT ... LIMIT $limit OFFSET $offset |
47 | |
48 | Supported by B<PostgreSQL> and B<SQLite> |
49 | |
50 | =cut |
7fca91be |
51 | sub _LimitOffset { |
fcb7fcbb |
52 | my ( $self, $sql, $rs_attrs, $rows, $offset ) = @_; |
53 | $sql .= $self->_parse_rs_attrs( $rs_attrs ) . " LIMIT ?"; |
54 | push @{$self->{limit_bind}}, [ $self->__rows_bindtype => $rows ]; |
55 | if ($offset) { |
56 | $sql .= " OFFSET ?"; |
57 | push @{$self->{limit_bind}}, [ $self->__offset_bindtype => $offset ]; |
58 | } |
7fca91be |
59 | return $sql; |
60 | } |
61 | |
d5dedbd6 |
62 | =head2 LimitXY |
63 | |
64 | SELECT ... LIMIT $offset $limit |
65 | |
66 | Supported by B<MySQL> and any L<SQL::Statement> based DBD |
67 | |
68 | =cut |
7fca91be |
69 | sub _LimitXY { |
fcb7fcbb |
70 | my ( $self, $sql, $rs_attrs, $rows, $offset ) = @_; |
71 | $sql .= $self->_parse_rs_attrs( $rs_attrs ) . " LIMIT "; |
72 | if ($offset) { |
73 | $sql .= '?, '; |
74 | push @{$self->{limit_bind}}, [ $self->__offset_bindtype => $offset ]; |
75 | } |
76 | $sql .= '?'; |
77 | push @{$self->{limit_bind}}, [ $self->__rows_bindtype => $rows ]; |
78 | |
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79 | return $sql; |
80 | } |
d5dedbd6 |
81 | |
82 | =head2 RowNumberOver |
83 | |
84 | SELECT * FROM ( |
85 | SELECT *, ROW_NUMBER() OVER( ORDER BY ... ) AS RNO__ROW__INDEX FROM ( |
86 | SELECT ... |
87 | ) |
88 | ) WHERE RNO__ROW__INDEX BETWEEN ($offset+1) AND ($limit+$offset) |
89 | |
90 | |
91 | ANSI standard Limit/Offset implementation. Supported by B<DB2> and |
92 | B<< MSSQL >= 2005 >>. |
93 | |
94 | =cut |
7fca91be |
95 | sub _RowNumberOver { |
96 | my ($self, $sql, $rs_attrs, $rows, $offset ) = @_; |
97 | |
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98 | # get selectors, and scan the order_by (if any) |
69d3c270 |
99 | my ($stripped_sql, $in_sel, $out_sel, $alias_map, $extra_order_sel) |
100 | = $self->_subqueried_limit_attrs ( $sql, $rs_attrs ); |
7fca91be |
101 | |
102 | # make up an order if none exists |
103 | my $requested_order = (delete $rs_attrs->{order_by}) || $self->_rno_default_order; |
104 | my $rno_ord = $self->_order_by ($requested_order); |
105 | |
106 | # this is the order supplement magic |
107 | my $mid_sel = $out_sel; |
108 | if ($extra_order_sel) { |
109 | for my $extra_col (sort |
110 | { $extra_order_sel->{$a} cmp $extra_order_sel->{$b} } |
111 | keys %$extra_order_sel |
112 | ) { |
113 | $in_sel .= sprintf (', %s AS %s', |
114 | $extra_col, |
115 | $extra_order_sel->{$extra_col}, |
116 | ); |
117 | |
118 | $mid_sel .= ', ' . $extra_order_sel->{$extra_col}; |
119 | } |
120 | } |
121 | |
122 | # and this is order re-alias magic |
123 | for ($extra_order_sel, $alias_map) { |
124 | for my $col (keys %$_) { |
125 | my $re_col = quotemeta ($col); |
126 | $rno_ord =~ s/$re_col/$_->{$col}/; |
127 | } |
128 | } |
129 | |
130 | # whatever is left of the order_by (only where is processed at this point) |
131 | my $group_having = $self->_parse_rs_attrs($rs_attrs); |
132 | |
133 | my $qalias = $self->_quote ($rs_attrs->{alias}); |
134 | my $idx_name = $self->_quote ('rno__row__index'); |
135 | |
69d3c270 |
136 | push @{$self->{limit_bind}}, [ $self->__offset_bindtype => $offset + 1], [ $self->__total_bindtype => $offset + $rows ]; |
137 | |
138 | return <<EOS; |
7fca91be |
139 | |
140 | SELECT $out_sel FROM ( |
141 | SELECT $mid_sel, ROW_NUMBER() OVER( $rno_ord ) AS $idx_name FROM ( |
69d3c270 |
142 | SELECT $in_sel ${stripped_sql}${group_having} |
7fca91be |
143 | ) $qalias |
fcb7fcbb |
144 | ) $qalias WHERE $idx_name >= ? AND $idx_name <= ? |
7fca91be |
145 | |
146 | EOS |
147 | |
7fca91be |
148 | } |
149 | |
150 | # some databases are happy with OVER (), some need OVER (ORDER BY (SELECT (1)) ) |
151 | sub _rno_default_order { |
152 | return undef; |
153 | } |
154 | |
d5dedbd6 |
155 | =head2 SkipFirst |
156 | |
157 | SELECT SKIP $offset FIRST $limit * FROM ... |
158 | |
159 | Suported by B<Informix>, almost like LimitOffset. According to |
160 | L<SQL::Abstract::Limit> C<... SKIP $offset LIMIT $limit ...> is also supported. |
161 | |
162 | =cut |
7fca91be |
163 | sub _SkipFirst { |
164 | my ($self, $sql, $rs_attrs, $rows, $offset) = @_; |
165 | |
166 | $sql =~ s/^ \s* SELECT \s+ //ix |
70c28808 |
167 | or $self->throw_exception("Unrecognizable SELECT: $sql"); |
7fca91be |
168 | |
169 | return sprintf ('SELECT %s%s%s%s', |
170 | $offset |
fcb7fcbb |
171 | ? do { |
172 | push @{$self->{limit_bind}}, [ $self->__offset_bindtype => $offset]; |
173 | 'SKIP ? ' |
174 | } |
7fca91be |
175 | : '' |
176 | , |
fcb7fcbb |
177 | do { |
178 | push @{$self->{limit_bind}}, [ $self->__rows_bindtype => $rows ]; |
179 | 'FIRST ? ' |
180 | }, |
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181 | $sql, |
182 | $self->_parse_rs_attrs ($rs_attrs), |
183 | ); |
184 | } |
185 | |
d5dedbd6 |
186 | =head2 FirstSkip |
187 | |
188 | SELECT FIRST $limit SKIP $offset * FROM ... |
189 | |
190 | Supported by B<Firebird/Interbase>, reverse of SkipFirst. According to |
191 | L<SQL::Abstract::Limit> C<... ROWS $limit TO $offset ...> is also supported. |
192 | |
193 | =cut |
7fca91be |
194 | sub _FirstSkip { |
195 | my ($self, $sql, $rs_attrs, $rows, $offset) = @_; |
196 | |
197 | $sql =~ s/^ \s* SELECT \s+ //ix |
70c28808 |
198 | or $self->throw_exception("Unrecognizable SELECT: $sql"); |
7fca91be |
199 | |
200 | return sprintf ('SELECT %s%s%s%s', |
fcb7fcbb |
201 | do { |
202 | push @{$self->{limit_bind}}, [ $self->__rows_bindtype => $rows ]; |
203 | 'FIRST ? ' |
204 | }, |
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205 | $offset |
fcb7fcbb |
206 | ? do { |
207 | push @{$self->{limit_bind}}, [ $self->__offset_bindtype => $offset]; |
208 | 'SKIP ? ' |
209 | } |
7fca91be |
210 | : '' |
211 | , |
212 | $sql, |
213 | $self->_parse_rs_attrs ($rs_attrs), |
214 | ); |
215 | } |
216 | |
6a6394f1 |
217 | |
d5dedbd6 |
218 | =head2 RowNum |
219 | |
6a6394f1 |
220 | Depending on the resultset attributes one of: |
221 | |
d5dedbd6 |
222 | SELECT * FROM ( |
223 | SELECT *, ROWNUM rownum__index FROM ( |
224 | SELECT ... |
d9672fb9 |
225 | ) WHERE ROWNUM <= ($limit+$offset) |
226 | ) WHERE rownum__index >= ($offset+1) |
d5dedbd6 |
227 | |
6a6394f1 |
228 | or |
229 | |
230 | SELECT * FROM ( |
231 | SELECT *, ROWNUM rownum__index FROM ( |
232 | SELECT ... |
233 | ) |
234 | ) WHERE rownum__index BETWEEN ($offset+1) AND ($limit+$offset) |
235 | |
236 | or |
237 | |
238 | SELECT * FROM ( |
239 | SELECT ... |
240 | ) WHERE ROWNUM <= ($limit+1) |
241 | |
d5dedbd6 |
242 | Supported by B<Oracle>. |
243 | |
244 | =cut |
7fca91be |
245 | sub _RowNum { |
246 | my ( $self, $sql, $rs_attrs, $rows, $offset ) = @_; |
247 | |
69d3c270 |
248 | my ($stripped_sql, $insel, $outsel) = $self->_subqueried_limit_attrs ($sql, $rs_attrs); |
7fca91be |
249 | |
250 | my $qalias = $self->_quote ($rs_attrs->{alias}); |
251 | my $idx_name = $self->_quote ('rownum__index'); |
252 | my $order_group_having = $self->_parse_rs_attrs($rs_attrs); |
253 | |
6a6394f1 |
254 | # |
255 | # There are two ways to limit in Oracle, one vastly faster than the other |
256 | # on large resultsets: https://decipherinfosys.wordpress.com/2007/08/09/paging-and-countstopkey-optimization/ |
257 | # However Oracle is retarded and does not preserve stable ROWNUM() values |
258 | # when called twice in the same scope. Therefore unless the resultset is |
259 | # ordered by a unique set of columns, it is not safe to use the faster |
260 | # method, and the slower BETWEEN query is used instead |
261 | # |
262 | # FIXME - this is quite expensive, and doe snot perform caching of any sort |
263 | # as soon as some of the DQ work becomes viable consider switching this |
264 | # over |
265 | if ( __order_by_is_unique($rs_attrs) ) { |
266 | |
267 | # if offset is 0 (first page) the we can skip a subquery |
268 | if (! $offset) { |
269 | push @{$self->{limit_bind}}, [ $self->__rows_bindtype => $rows ]; |
270 | |
271 | return <<EOS; |
272 | SELECT $outsel FROM ( |
273 | SELECT $insel ${stripped_sql}${order_group_having} |
274 | ) $qalias WHERE ROWNUM <= ? |
275 | EOS |
276 | } |
277 | else { |
278 | push @{$self->{limit_bind}}, [ $self->__total_bindtype => $offset + $rows ], [ $self->__offset_bindtype => $offset + 1 ]; |
69d3c270 |
279 | |
6a6394f1 |
280 | return <<EOS; |
7fca91be |
281 | SELECT $outsel FROM ( |
282 | SELECT $outsel, ROWNUM $idx_name FROM ( |
69d3c270 |
283 | SELECT $insel ${stripped_sql}${order_group_having} |
fcb7fcbb |
284 | ) $qalias WHERE ROWNUM <= ? |
285 | ) $qalias WHERE $idx_name >= ? |
7fca91be |
286 | EOS |
6a6394f1 |
287 | } |
d9672fb9 |
288 | } |
289 | else { |
6a6394f1 |
290 | push @{$self->{limit_bind}}, [ $self->__offset_bindtype => $offset + 1 ], [ $self->__total_bindtype => $offset + $rows ]; |
69d3c270 |
291 | |
292 | return <<EOS; |
6a6394f1 |
293 | SELECT $outsel FROM ( |
294 | SELECT $outsel, ROWNUM $idx_name FROM ( |
69d3c270 |
295 | SELECT $insel ${stripped_sql}${order_group_having} |
6a6394f1 |
296 | ) $qalias |
297 | ) $qalias WHERE $idx_name BETWEEN ? AND ? |
d9672fb9 |
298 | EOS |
6a6394f1 |
299 | } |
300 | } |
7fca91be |
301 | |
6a6394f1 |
302 | # determine if the supplied order_by contains a unique column (set) |
303 | sub __order_by_is_unique { |
304 | my $rs_attrs = shift; |
305 | my $rsrc = $rs_attrs->{_rsroot_rsrc}; |
306 | my $order_by = $rs_attrs->{order_by} |
307 | || return 0; |
308 | |
309 | my $storage = $rsrc->schema->storage; |
310 | |
311 | my @order_by_cols = map { $_->[0] } $storage->_extract_order_criteria($order_by) |
312 | or return 0; |
313 | |
314 | my $colinfo = |
315 | $storage->_resolve_column_info($rs_attrs->{from}, \@order_by_cols); |
316 | |
317 | my $sources = { |
318 | map {( "$_" => $_ )} map { $_->{-result_source} } values %$colinfo |
319 | }; |
320 | |
321 | my $supplied_order = { |
322 | map { $_ => 1 } |
323 | grep { exists $colinfo->{$_} and ! $colinfo->{$_}{is_nullable} } |
324 | @order_by_cols |
325 | }; |
326 | |
327 | return 0 unless keys %$supplied_order; |
328 | |
329 | for my $uks ( |
330 | map { values %$_ } map { +{ $_->unique_constraints } } values %$sources |
331 | ) { |
332 | return 1 |
333 | unless first { ! exists $supplied_order->{$_} } @$uks; |
69d3c270 |
334 | } |
6a6394f1 |
335 | |
336 | return 0; |
7fca91be |
337 | } |
338 | |
6a6394f1 |
339 | # used by _Top and _FetchFirst below |
96eacdb7 |
340 | sub _prep_for_skimming_limit { |
341 | my ( $self, $sql, $rs_attrs ) = @_; |
7fca91be |
342 | |
7fca91be |
343 | # get selectors |
69d3c270 |
344 | my (%r, $alias_map, $extra_order_sel); |
345 | ($r{inner_sql}, $r{in_sel}, $r{out_sel}, $alias_map, $extra_order_sel) |
346 | = $self->_subqueried_limit_attrs ($sql, $rs_attrs); |
7fca91be |
347 | |
348 | my $requested_order = delete $rs_attrs->{order_by}; |
96eacdb7 |
349 | $r{order_by_requested} = $self->_order_by ($requested_order); |
7fca91be |
350 | |
351 | # make up an order unless supplied |
96eacdb7 |
352 | my $inner_order = ($r{order_by_requested} |
7fca91be |
353 | ? $requested_order |
354 | : [ map |
3f5b99fe |
355 | { "$rs_attrs->{alias}.$_" } |
4376a157 |
356 | ( $rs_attrs->{_rsroot_rsrc}->_pri_cols ) |
7fca91be |
357 | ] |
358 | ); |
359 | |
7fca91be |
360 | # localise as we already have all the bind values we need |
361 | { |
362 | local $self->{order_bind}; |
96eacdb7 |
363 | $r{order_by_inner} = $self->_order_by ($inner_order); |
7fca91be |
364 | |
365 | my @out_chunks; |
366 | for my $ch ($self->_order_by_chunks ($inner_order)) { |
367 | $ch = $ch->[0] if ref $ch eq 'ARRAY'; |
368 | |
369 | $ch =~ s/\s+ ( ASC|DESC ) \s* $//ix; |
370 | my $dir = uc ($1||'ASC'); |
371 | |
372 | push @out_chunks, \join (' ', $ch, $dir eq 'ASC' ? 'DESC' : 'ASC' ); |
373 | } |
374 | |
96eacdb7 |
375 | $r{order_by_reversed} = $self->_order_by (\@out_chunks); |
7fca91be |
376 | } |
377 | |
378 | # this is the order supplement magic |
96eacdb7 |
379 | $r{mid_sel} = $r{out_sel}; |
7fca91be |
380 | if ($extra_order_sel) { |
381 | for my $extra_col (sort |
382 | { $extra_order_sel->{$a} cmp $extra_order_sel->{$b} } |
383 | keys %$extra_order_sel |
384 | ) { |
96eacdb7 |
385 | $r{in_sel} .= sprintf (', %s AS %s', |
7fca91be |
386 | $extra_col, |
387 | $extra_order_sel->{$extra_col}, |
388 | ); |
389 | |
96eacdb7 |
390 | $r{mid_sel} .= ', ' . $extra_order_sel->{$extra_col}; |
7fca91be |
391 | } |
392 | |
393 | # since whatever order bindvals there are, they will be realiased |
394 | # and need to show up in front of the entire initial inner subquery |
4c2b30d6 |
395 | # *unshift* the selector bind stack to make this happen (horrible, |
396 | # horrible, but we don't have another mechanism yet) |
397 | unshift @{$self->{select_bind}}, @{$self->{order_bind}}; |
7fca91be |
398 | } |
399 | |
400 | # and this is order re-alias magic |
401 | for my $map ($extra_order_sel, $alias_map) { |
402 | for my $col (keys %$map) { |
403 | my $re_col = quotemeta ($col); |
404 | $_ =~ s/$re_col/$map->{$col}/ |
96eacdb7 |
405 | for ($r{order_by_reversed}, $r{order_by_requested}); |
7fca91be |
406 | } |
407 | } |
408 | |
409 | # generate the rest of the sql |
96eacdb7 |
410 | $r{grpby_having} = $self->_parse_rs_attrs ($rs_attrs); |
7fca91be |
411 | |
96eacdb7 |
412 | $r{quoted_rs_alias} = $self->_quote ($rs_attrs->{alias}); |
413 | |
414 | \%r; |
415 | } |
416 | |
417 | =head2 Top |
418 | |
419 | SELECT * FROM |
420 | |
421 | SELECT TOP $limit FROM ( |
422 | SELECT TOP $limit FROM ( |
423 | SELECT TOP ($limit+$offset) ... |
424 | ) ORDER BY $reversed_original_order |
425 | ) ORDER BY $original_order |
426 | |
427 | Unreliable Top-based implementation, supported by B<< MSSQL < 2005 >>. |
428 | |
429 | =head3 CAVEAT |
430 | |
431 | Due to its implementation, this limit dialect returns B<incorrect results> |
432 | when $limit+$offset > total amount of rows in the resultset. |
433 | |
434 | =cut |
435 | |
436 | sub _Top { |
437 | my ( $self, $sql, $rs_attrs, $rows, $offset ) = @_; |
438 | |
439 | my %l = %{ $self->_prep_for_skimming_limit($sql, $rs_attrs) }; |
7fca91be |
440 | |
441 | $sql = sprintf ('SELECT TOP %u %s %s %s %s', |
442 | $rows + ($offset||0), |
96eacdb7 |
443 | $l{in_sel}, |
444 | $l{inner_sql}, |
445 | $l{grpby_having}, |
446 | $l{order_by_inner}, |
7fca91be |
447 | ); |
448 | |
449 | $sql = sprintf ('SELECT TOP %u %s FROM ( %s ) %s %s', |
450 | $rows, |
96eacdb7 |
451 | $l{mid_sel}, |
7fca91be |
452 | $sql, |
96eacdb7 |
453 | $l{quoted_rs_alias}, |
454 | $l{order_by_reversed}, |
7fca91be |
455 | ) if $offset; |
456 | |
457 | $sql = sprintf ('SELECT TOP %u %s FROM ( %s ) %s %s', |
458 | $rows, |
96eacdb7 |
459 | $l{out_sel}, |
460 | $sql, |
461 | $l{quoted_rs_alias}, |
462 | $l{order_by_requested}, |
463 | ) if ( ($offset && $l{order_by_requested}) || ($l{mid_sel} ne $l{out_sel}) ); |
464 | |
465 | return $sql; |
466 | } |
467 | |
468 | =head2 FetchFirst |
469 | |
470 | SELECT * FROM |
471 | ( |
472 | SELECT * FROM ( |
473 | SELECT * FROM ( |
474 | SELECT * FROM ... |
475 | ) ORDER BY $reversed_original_order |
476 | FETCH FIRST $limit ROWS ONLY |
477 | ) ORDER BY $original_order |
478 | FETCH FIRST $limit ROWS ONLY |
479 | ) |
480 | |
481 | Unreliable FetchFirst-based implementation, supported by B<< IBM DB2 <= V5R3 >>. |
482 | |
483 | =head3 CAVEAT |
484 | |
485 | Due to its implementation, this limit dialect returns B<incorrect results> |
486 | when $limit+$offset > total amount of rows in the resultset. |
487 | |
488 | =cut |
489 | |
490 | sub _FetchFirst { |
491 | my ( $self, $sql, $rs_attrs, $rows, $offset ) = @_; |
492 | |
493 | my %l = %{ $self->_prep_for_skimming_limit($sql, $rs_attrs) }; |
494 | |
495 | $sql = sprintf ('SELECT %s %s %s %s FETCH FIRST %u ROWS ONLY', |
496 | $l{in_sel}, |
497 | $l{inner_sql}, |
498 | $l{grpby_having}, |
499 | $l{order_by_inner}, |
500 | $rows + ($offset||0), |
501 | ); |
502 | |
503 | $sql = sprintf ('SELECT %s FROM ( %s ) %s %s FETCH FIRST %u ROWS ONLY', |
504 | $l{mid_sel}, |
505 | $sql, |
506 | $l{quoted_rs_alias}, |
507 | $l{order_by_reversed}, |
508 | $rows, |
509 | ) if $offset; |
510 | |
511 | $sql = sprintf ('SELECT %s FROM ( %s ) %s %s FETCH FIRST %u ROWS ONLY', |
512 | $l{out_sel}, |
7fca91be |
513 | $sql, |
96eacdb7 |
514 | $l{quoted_rs_alias}, |
515 | $l{order_by_requested}, |
516 | $rows, |
517 | ) if ( ($offset && $l{order_by_requested}) || ($l{mid_sel} ne $l{out_sel}) ); |
7fca91be |
518 | |
7fca91be |
519 | return $sql; |
520 | } |
521 | |
d5dedbd6 |
522 | =head2 RowCountOrGenericSubQ |
523 | |
524 | This is not exactly a limit dialect, but more of a proxy for B<Sybase ASE>. |
525 | If no $offset is supplied the limit is simply performed as: |
526 | |
527 | SET ROWCOUNT $limit |
528 | SELECT ... |
529 | SET ROWCOUNT 0 |
530 | |
531 | Otherwise we fall back to L</GenericSubQ> |
532 | |
533 | =cut |
96eacdb7 |
534 | |
7fca91be |
535 | sub _RowCountOrGenericSubQ { |
536 | my $self = shift; |
537 | my ($sql, $rs_attrs, $rows, $offset) = @_; |
538 | |
539 | return $self->_GenericSubQ(@_) if $offset; |
540 | |
541 | return sprintf <<"EOF", $rows, $sql; |
542 | SET ROWCOUNT %d |
543 | %s |
544 | SET ROWCOUNT 0 |
545 | EOF |
546 | } |
547 | |
d5dedbd6 |
548 | =head2 GenericSubQ |
549 | |
550 | SELECT * FROM ( |
551 | SELECT ... |
552 | ) |
553 | WHERE ( |
554 | SELECT COUNT(*) FROM $original_table cnt WHERE cnt.id < $original_table.id |
555 | ) BETWEEN $offset AND ($offset+$rows-1) |
556 | |
557 | This is the most evil limit "dialect" (more of a hack) for I<really> stupid |
558 | databases. It works by ordering the set by some unique column, and calculating |
559 | the amount of rows that have a less-er value (thus emulating a L</RowNum>-like |
560 | index). Of course this implies the set can only be ordered by a single unique |
561 | column. Also note that this technique can be and often is B<excruciatingly |
562 | slow>. |
563 | |
564 | Currently used by B<Sybase ASE>, due to lack of any other option. |
565 | |
566 | =cut |
7fca91be |
567 | sub _GenericSubQ { |
568 | my ($self, $sql, $rs_attrs, $rows, $offset) = @_; |
569 | |
4376a157 |
570 | my $root_rsrc = $rs_attrs->{_rsroot_rsrc}; |
7fca91be |
571 | my $root_tbl_name = $root_rsrc->name; |
572 | |
7fca91be |
573 | my ($order_by, @rest) = do { |
574 | local $self->{quote_char}; |
575 | $self->_order_by_chunks ($rs_attrs->{order_by}) |
576 | }; |
577 | |
578 | unless ( |
579 | $order_by |
580 | && |
581 | ! @rest |
582 | && |
583 | ( ! ref $order_by |
584 | || |
585 | ( ref $order_by eq 'ARRAY' and @$order_by == 1 ) |
586 | ) |
587 | ) { |
70c28808 |
588 | $self->throw_exception ( |
7fca91be |
589 | 'Generic Subquery Limit does not work on resultsets without an order, or resultsets ' |
590 | . 'with complex order criteria (multicolumn and/or functions). Provide a single, ' |
591 | . 'unique-column order criteria.' |
592 | ); |
593 | } |
594 | |
595 | ($order_by) = @$order_by if ref $order_by; |
596 | |
597 | $order_by =~ s/\s+ ( ASC|DESC ) \s* $//ix; |
598 | my $direction = lc ($1 || 'asc'); |
599 | |
600 | my ($unq_sort_col) = $order_by =~ /(?:^|\.)([^\.]+)$/; |
601 | |
602 | my $inf = $root_rsrc->storage->_resolve_column_info ( |
603 | $rs_attrs->{from}, [$order_by, $unq_sort_col] |
604 | ); |
605 | |
70c28808 |
606 | my $ord_colinfo = $inf->{$order_by} || $self->throw_exception("Unable to determine source of order-criteria '$order_by'"); |
7fca91be |
607 | |
608 | if ($ord_colinfo->{-result_source}->name ne $root_tbl_name) { |
70c28808 |
609 | $self->throw_exception(sprintf |
610 | "Generic Subquery Limit order criteria can be only based on the root-source '%s'" |
611 | . " (aliased as '%s')", $root_rsrc->source_name, $rs_attrs->{alias}, |
612 | ); |
7fca91be |
613 | } |
614 | |
615 | # make sure order column is qualified |
616 | $order_by = "$rs_attrs->{alias}.$order_by" |
617 | unless $order_by =~ /^$rs_attrs->{alias}\./; |
618 | |
619 | my $is_u; |
620 | my $ucs = { $root_rsrc->unique_constraints }; |
621 | for (values %$ucs ) { |
622 | if (@$_ == 1 && "$rs_attrs->{alias}.$_->[0]" eq $order_by) { |
623 | $is_u++; |
624 | last; |
625 | } |
626 | } |
70c28808 |
627 | $self->throw_exception( |
628 | "Generic Subquery Limit order criteria column '$order_by' must be unique (no unique constraint found)" |
629 | ) unless $is_u; |
7fca91be |
630 | |
69d3c270 |
631 | my ($stripped_sql, $in_sel, $out_sel, $alias_map, $extra_order_sel) |
632 | = $self->_subqueried_limit_attrs ($sql, $rs_attrs); |
7fca91be |
633 | |
634 | my $cmp_op = $direction eq 'desc' ? '>' : '<'; |
635 | my $count_tbl_alias = 'rownum__emulation'; |
636 | |
637 | my $order_sql = $self->_order_by (delete $rs_attrs->{order_by}); |
638 | my $group_having_sql = $self->_parse_rs_attrs($rs_attrs); |
639 | |
640 | # add the order supplement (if any) as this is what will be used for the outer WHERE |
641 | $in_sel .= ", $_" for keys %{$extra_order_sel||{}}; |
642 | |
69d3c270 |
643 | my $rownum_cond; |
644 | if ($offset) { |
645 | $rownum_cond = 'BETWEEN ? AND ?'; |
646 | |
647 | push @{$self->{limit_bind}}, |
648 | [ $self->__offset_bindtype => $offset ], |
649 | [ $self->__total_bindtype => $offset + $rows - 1] |
650 | ; |
651 | } |
652 | else { |
653 | $rownum_cond = '< ?'; |
654 | |
655 | push @{$self->{limit_bind}}, |
656 | [ $self->__rows_bindtype => $rows ] |
657 | ; |
658 | } |
659 | |
660 | return sprintf (" |
7fca91be |
661 | SELECT $out_sel |
662 | FROM ( |
69d3c270 |
663 | SELECT $in_sel ${stripped_sql}${group_having_sql} |
7fca91be |
664 | ) %s |
69d3c270 |
665 | WHERE ( SELECT COUNT(*) FROM %s %s WHERE %s $cmp_op %s ) $rownum_cond |
7fca91be |
666 | $order_sql |
69d3c270 |
667 | ", map { $self->_quote ($_) } ( |
668 | $rs_attrs->{alias}, |
669 | $root_tbl_name, |
670 | $count_tbl_alias, |
671 | "$count_tbl_alias.$unq_sort_col", |
672 | $order_by, |
673 | )); |
7fca91be |
674 | } |
675 | |
676 | |
677 | # !!! THIS IS ALSO HORRIFIC !!! /me ashamed |
678 | # |
679 | # Generates inner/outer select lists for various limit dialects |
680 | # which result in one or more subqueries (e.g. RNO, Top, RowNum) |
681 | # Any non-root-table columns need to have their table qualifier |
682 | # turned into a column alias (otherwise names in subqueries clash |
683 | # and/or lose their source table) |
684 | # |
69d3c270 |
685 | # Returns mangled proto-sql, inner/outer strings of SQL QUOTED selectors |
686 | # with aliases (to be used in whatever select statement), and an alias |
687 | # index hashref of QUOTED SEL => QUOTED ALIAS pairs (to maybe be used |
688 | # for string-subst higher up). |
7fca91be |
689 | # If an order_by is supplied, the inner select needs to bring out columns |
690 | # used in implicit (non-selected) orders, and the order condition itself |
691 | # needs to be realiased to the proper names in the outer query. Thus we |
692 | # also return a hashref (order doesn't matter) of QUOTED EXTRA-SEL => |
693 | # QUOTED ALIAS pairs, which is a list of extra selectors that do *not* |
694 | # exist in the original select list |
7fca91be |
695 | sub _subqueried_limit_attrs { |
69d3c270 |
696 | my ($self, $proto_sql, $rs_attrs) = @_; |
7fca91be |
697 | |
70c28808 |
698 | $self->throw_exception( |
699 | 'Limit dialect implementation usable only in the context of DBIC (missing $rs_attrs)' |
700 | ) unless ref ($rs_attrs) eq 'HASH'; |
7fca91be |
701 | |
f74d22e2 |
702 | # mangle the input sql as we will be replacing the selector entirely |
703 | unless ( |
704 | $rs_attrs->{_selector_sql} |
705 | and |
706 | $proto_sql =~ s/^ \s* SELECT \s* \Q$rs_attrs->{_selector_sql}//ix |
707 | ) { |
708 | $self->throw_exception("Unrecognizable SELECT: $proto_sql"); |
709 | } |
69d3c270 |
710 | |
3f5b99fe |
711 | my ($re_sep, $re_alias) = map { quotemeta $_ } ( $self->{name_sep}, $rs_attrs->{alias} ); |
7fca91be |
712 | |
69d3c270 |
713 | # insulate from the multiple _recurse_fields calls below |
714 | local $self->{select_bind}; |
715 | |
7fca91be |
716 | # correlate select and as, build selection index |
717 | my (@sel, $in_sel_index); |
718 | for my $i (0 .. $#{$rs_attrs->{select}}) { |
719 | |
720 | my $s = $rs_attrs->{select}[$i]; |
721 | my $sql_sel = $self->_recurse_fields ($s); |
722 | my $sql_alias = (ref $s) eq 'HASH' ? $s->{-as} : undef; |
723 | |
7fca91be |
724 | push @sel, { |
725 | sql => $sql_sel, |
69d3c270 |
726 | unquoted_sql => do { |
727 | local $self->{quote_char}; |
728 | $self->_recurse_fields ($s); |
729 | }, |
7fca91be |
730 | as => |
731 | $sql_alias |
732 | || |
733 | $rs_attrs->{as}[$i] |
734 | || |
70c28808 |
735 | $self->throw_exception("Select argument $i ($s) without corresponding 'as'") |
7fca91be |
736 | , |
737 | }; |
738 | |
739 | $in_sel_index->{$sql_sel}++; |
740 | $in_sel_index->{$self->_quote ($sql_alias)}++ if $sql_alias; |
741 | |
742 | # record unqualified versions too, so we do not have |
743 | # to reselect the same column twice (in qualified and |
744 | # unqualified form) |
745 | if (! ref $s && $sql_sel =~ / $re_sep (.+) $/x) { |
746 | $in_sel_index->{$1}++; |
747 | } |
748 | } |
749 | |
750 | |
751 | # re-alias and remove any name separators from aliases, |
752 | # unless we are dealing with the current source alias |
753 | # (which will transcend the subqueries as it is necessary |
754 | # for possible further chaining) |
755 | my (@in_sel, @out_sel, %renamed); |
756 | for my $node (@sel) { |
3f5b99fe |
757 | if ( |
758 | $node->{as} =~ / (?<! ^ $re_alias ) \. /x |
759 | or |
760 | $node->{unquoted_sql} =~ / (?<! ^ $re_alias ) $re_sep /x |
761 | ) { |
7fca91be |
762 | $node->{as} = $self->_unqualify_colname($node->{as}); |
763 | my $quoted_as = $self->_quote($node->{as}); |
764 | push @in_sel, sprintf '%s AS %s', $node->{sql}, $quoted_as; |
765 | push @out_sel, $quoted_as; |
766 | $renamed{$node->{sql}} = $quoted_as; |
767 | } |
768 | else { |
769 | push @in_sel, $node->{sql}; |
770 | push @out_sel, $self->_quote ($node->{as}); |
771 | } |
772 | } |
7fca91be |
773 | # see if the order gives us anything |
774 | my %extra_order_sel; |
775 | for my $chunk ($self->_order_by_chunks ($rs_attrs->{order_by})) { |
776 | # order with bind |
777 | $chunk = $chunk->[0] if (ref $chunk) eq 'ARRAY'; |
778 | $chunk =~ s/\s+ (?: ASC|DESC ) \s* $//ix; |
779 | |
780 | next if $in_sel_index->{$chunk}; |
781 | |
782 | $extra_order_sel{$chunk} ||= $self->_quote ( |
783 | 'ORDER__BY__' . scalar keys %extra_order_sel |
784 | ); |
785 | } |
786 | |
787 | return ( |
69d3c270 |
788 | $proto_sql, |
7fca91be |
789 | (map { join (', ', @$_ ) } ( |
790 | \@in_sel, |
791 | \@out_sel) |
792 | ), |
793 | \%renamed, |
794 | keys %extra_order_sel ? \%extra_order_sel : (), |
795 | ); |
796 | } |
797 | |
798 | sub _unqualify_colname { |
799 | my ($self, $fqcn) = @_; |
3f5b99fe |
800 | $fqcn =~ s/ \. /__/xg; |
7fca91be |
801 | return $fqcn; |
802 | } |
803 | |
804 | 1; |
d5dedbd6 |
805 | |
806 | =head1 AUTHORS |
807 | |
808 | See L<DBIx::Class/CONTRIBUTORS>. |
809 | |
810 | =head1 LICENSE |
811 | |
812 | You may distribute this code under the same terms as Perl itself. |
813 | |
814 | =cut |