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1 | package DBIx::Class::SQLMaker::LimitDialects; |
7fca91be |
2 | |
3 | use warnings; |
4 | use strict; |
5 | |
7fca91be |
6 | use List::Util 'first'; |
7 | use namespace::clean; |
8 | |
fcb7fcbb |
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 | |
7fca91be |
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 | |
7fca91be |
98 | # get selectors, and scan the order_by (if any) |
cecf64bc |
99 | my $sq_attrs = $self->_subqueried_limit_attrs ( $sql, $rs_attrs ); |
7fca91be |
100 | |
101 | # make up an order if none exists |
102 | my $requested_order = (delete $rs_attrs->{order_by}) || $self->_rno_default_order; |
ebc5c60a |
103 | |
104 | # the order binds (if any) will need to go at the end of the entire inner select |
105 | local $self->{order_bind}; |
7fca91be |
106 | my $rno_ord = $self->_order_by ($requested_order); |
ebc5c60a |
107 | push @{$self->{select_bind}}, @{$self->{order_bind}}; |
7fca91be |
108 | |
109 | # this is the order supplement magic |
cecf64bc |
110 | my $mid_sel = $sq_attrs->{selection_outer}; |
111 | if (my $extra_order_sel = $sq_attrs->{order_supplement}) { |
7fca91be |
112 | for my $extra_col (sort |
113 | { $extra_order_sel->{$a} cmp $extra_order_sel->{$b} } |
114 | keys %$extra_order_sel |
115 | ) { |
cecf64bc |
116 | $sq_attrs->{selection_inner} .= sprintf (', %s AS %s', |
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117 | $extra_col, |
118 | $extra_order_sel->{$extra_col}, |
119 | ); |
7fca91be |
120 | } |
121 | } |
122 | |
123 | # and this is order re-alias magic |
833733fe |
124 | for my $map ($sq_attrs->{order_supplement}, $sq_attrs->{outer_renames}) { |
125 | for my $col (sort { (length $b) <=> (length $a) } keys %{$map||{}} ) { |
7fca91be |
126 | my $re_col = quotemeta ($col); |
833733fe |
127 | $rno_ord =~ s/$re_col/$map->{$col}/; |
7fca91be |
128 | } |
129 | } |
130 | |
131 | # whatever is left of the order_by (only where is processed at this point) |
132 | my $group_having = $self->_parse_rs_attrs($rs_attrs); |
133 | |
134 | my $qalias = $self->_quote ($rs_attrs->{alias}); |
135 | my $idx_name = $self->_quote ('rno__row__index'); |
136 | |
69d3c270 |
137 | push @{$self->{limit_bind}}, [ $self->__offset_bindtype => $offset + 1], [ $self->__total_bindtype => $offset + $rows ]; |
138 | |
139 | return <<EOS; |
7fca91be |
140 | |
cecf64bc |
141 | SELECT $sq_attrs->{selection_outer} FROM ( |
7fca91be |
142 | SELECT $mid_sel, ROW_NUMBER() OVER( $rno_ord ) AS $idx_name FROM ( |
cecf64bc |
143 | SELECT $sq_attrs->{selection_inner} $sq_attrs->{query_leftover}${group_having} |
7fca91be |
144 | ) $qalias |
fcb7fcbb |
145 | ) $qalias WHERE $idx_name >= ? AND $idx_name <= ? |
7fca91be |
146 | |
147 | EOS |
148 | |
7fca91be |
149 | } |
150 | |
151 | # some databases are happy with OVER (), some need OVER (ORDER BY (SELECT (1)) ) |
152 | sub _rno_default_order { |
153 | return undef; |
154 | } |
155 | |
f895c500 |
156 | =head2 OffsetFetchNext |
157 | |
158 | SELECT * FROM ... OFFSET 10 ROWS FETCH NEXT 5 ROWS ONLY |
159 | |
160 | Suported by B<SQL Server 2012>, purported to be more efficient than L</RowNumberOver>. |
161 | |
162 | =cut |
163 | sub _OffsetFetchNext { |
164 | my ($self, $sql, $rs_attrs, $rows, $offset ) = @_; |
165 | |
166 | my $requested_order = (delete $rs_attrs->{order_by}) || \'1'; |
167 | |
168 | my $ord = $self->_order_by ($requested_order) || ' ORDER BY 1'; |
169 | |
170 | $sql .= $self->_parse_rs_attrs( $rs_attrs ) |
171 | . $ord |
172 | . ' OFFSET ? ROWS FETCH NEXT ? ROWS ONLY'; |
173 | push @{$self->{limit_bind}}, |
174 | [ $self->__offset_bindtype => $offset || 0], |
175 | [ $self->__rows_bindtype => $rows]; |
176 | |
177 | return $sql; |
178 | } |
179 | |
d5dedbd6 |
180 | =head2 SkipFirst |
181 | |
182 | SELECT SKIP $offset FIRST $limit * FROM ... |
183 | |
184 | Suported by B<Informix>, almost like LimitOffset. According to |
185 | L<SQL::Abstract::Limit> C<... SKIP $offset LIMIT $limit ...> is also supported. |
186 | |
187 | =cut |
7fca91be |
188 | sub _SkipFirst { |
189 | my ($self, $sql, $rs_attrs, $rows, $offset) = @_; |
190 | |
191 | $sql =~ s/^ \s* SELECT \s+ //ix |
70c28808 |
192 | or $self->throw_exception("Unrecognizable SELECT: $sql"); |
7fca91be |
193 | |
194 | return sprintf ('SELECT %s%s%s%s', |
195 | $offset |
fcb7fcbb |
196 | ? do { |
8b31f62e |
197 | push @{$self->{pre_select_bind}}, [ $self->__offset_bindtype => $offset]; |
fcb7fcbb |
198 | 'SKIP ? ' |
199 | } |
7fca91be |
200 | : '' |
201 | , |
fcb7fcbb |
202 | do { |
8b31f62e |
203 | push @{$self->{pre_select_bind}}, [ $self->__rows_bindtype => $rows ]; |
fcb7fcbb |
204 | 'FIRST ? ' |
205 | }, |
7fca91be |
206 | $sql, |
207 | $self->_parse_rs_attrs ($rs_attrs), |
208 | ); |
209 | } |
210 | |
d5dedbd6 |
211 | =head2 FirstSkip |
212 | |
213 | SELECT FIRST $limit SKIP $offset * FROM ... |
214 | |
215 | Supported by B<Firebird/Interbase>, reverse of SkipFirst. According to |
216 | L<SQL::Abstract::Limit> C<... ROWS $limit TO $offset ...> is also supported. |
217 | |
218 | =cut |
7fca91be |
219 | sub _FirstSkip { |
220 | my ($self, $sql, $rs_attrs, $rows, $offset) = @_; |
221 | |
222 | $sql =~ s/^ \s* SELECT \s+ //ix |
70c28808 |
223 | or $self->throw_exception("Unrecognizable SELECT: $sql"); |
7fca91be |
224 | |
225 | return sprintf ('SELECT %s%s%s%s', |
fcb7fcbb |
226 | do { |
8b31f62e |
227 | push @{$self->{pre_select_bind}}, [ $self->__rows_bindtype => $rows ]; |
fcb7fcbb |
228 | 'FIRST ? ' |
229 | }, |
7fca91be |
230 | $offset |
fcb7fcbb |
231 | ? do { |
8b31f62e |
232 | push @{$self->{pre_select_bind}}, [ $self->__offset_bindtype => $offset]; |
fcb7fcbb |
233 | 'SKIP ? ' |
234 | } |
7fca91be |
235 | : '' |
236 | , |
237 | $sql, |
238 | $self->_parse_rs_attrs ($rs_attrs), |
239 | ); |
240 | } |
241 | |
6a6394f1 |
242 | |
d5dedbd6 |
243 | =head2 RowNum |
244 | |
6a6394f1 |
245 | Depending on the resultset attributes one of: |
246 | |
d5dedbd6 |
247 | SELECT * FROM ( |
b775fa8e |
248 | SELECT *, ROWNUM AS rownum__index FROM ( |
d5dedbd6 |
249 | SELECT ... |
d9672fb9 |
250 | ) WHERE ROWNUM <= ($limit+$offset) |
251 | ) WHERE rownum__index >= ($offset+1) |
d5dedbd6 |
252 | |
6a6394f1 |
253 | or |
254 | |
255 | SELECT * FROM ( |
b775fa8e |
256 | SELECT *, ROWNUM AS rownum__index FROM ( |
6a6394f1 |
257 | SELECT ... |
258 | ) |
259 | ) WHERE rownum__index BETWEEN ($offset+1) AND ($limit+$offset) |
260 | |
261 | or |
262 | |
263 | SELECT * FROM ( |
264 | SELECT ... |
265 | ) WHERE ROWNUM <= ($limit+1) |
266 | |
d5dedbd6 |
267 | Supported by B<Oracle>. |
268 | |
269 | =cut |
7fca91be |
270 | sub _RowNum { |
271 | my ( $self, $sql, $rs_attrs, $rows, $offset ) = @_; |
272 | |
cecf64bc |
273 | my $sq_attrs = $self->_subqueried_limit_attrs ($sql, $rs_attrs); |
7fca91be |
274 | |
275 | my $qalias = $self->_quote ($rs_attrs->{alias}); |
276 | my $idx_name = $self->_quote ('rownum__index'); |
277 | my $order_group_having = $self->_parse_rs_attrs($rs_attrs); |
278 | |
cccd1876 |
279 | |
280 | # if no offset (e.g. first page) - we can skip one of the subqueries |
281 | if (! $offset) { |
282 | push @{$self->{limit_bind}}, [ $self->__rows_bindtype => $rows ]; |
283 | |
284 | return <<EOS; |
cecf64bc |
285 | SELECT $sq_attrs->{selection_outer} FROM ( |
286 | SELECT $sq_attrs->{selection_inner} $sq_attrs->{query_leftover}${order_group_having} |
cccd1876 |
287 | ) $qalias WHERE ROWNUM <= ? |
288 | EOS |
289 | } |
290 | |
6a6394f1 |
291 | # |
292 | # There are two ways to limit in Oracle, one vastly faster than the other |
293 | # on large resultsets: https://decipherinfosys.wordpress.com/2007/08/09/paging-and-countstopkey-optimization/ |
294 | # However Oracle is retarded and does not preserve stable ROWNUM() values |
295 | # when called twice in the same scope. Therefore unless the resultset is |
296 | # ordered by a unique set of columns, it is not safe to use the faster |
297 | # method, and the slower BETWEEN query is used instead |
298 | # |
7cec4356 |
299 | # FIXME - this is quite expensive, and does not perform caching of any sort |
6a6394f1 |
300 | # as soon as some of the DQ work becomes viable consider switching this |
301 | # over |
7cec4356 |
302 | if ( |
303 | $rs_attrs->{order_by} |
304 | and |
305 | $rs_attrs->{_rsroot_rsrc}->storage->_order_by_is_stable( |
5f11e54f |
306 | @{$rs_attrs}{qw/from order_by where/} |
7cec4356 |
307 | ) |
308 | ) { |
cccd1876 |
309 | push @{$self->{limit_bind}}, [ $self->__total_bindtype => $offset + $rows ], [ $self->__offset_bindtype => $offset + 1 ]; |
6a6394f1 |
310 | |
cccd1876 |
311 | return <<EOS; |
cecf64bc |
312 | SELECT $sq_attrs->{selection_outer} FROM ( |
b775fa8e |
313 | SELECT $sq_attrs->{selection_outer}, ROWNUM AS $idx_name FROM ( |
cecf64bc |
314 | SELECT $sq_attrs->{selection_inner} $sq_attrs->{query_leftover}${order_group_having} |
fcb7fcbb |
315 | ) $qalias WHERE ROWNUM <= ? |
316 | ) $qalias WHERE $idx_name >= ? |
7fca91be |
317 | EOS |
d9672fb9 |
318 | } |
319 | else { |
6a6394f1 |
320 | push @{$self->{limit_bind}}, [ $self->__offset_bindtype => $offset + 1 ], [ $self->__total_bindtype => $offset + $rows ]; |
69d3c270 |
321 | |
322 | return <<EOS; |
cecf64bc |
323 | SELECT $sq_attrs->{selection_outer} FROM ( |
b775fa8e |
324 | SELECT $sq_attrs->{selection_outer}, ROWNUM AS $idx_name FROM ( |
cecf64bc |
325 | SELECT $sq_attrs->{selection_inner} $sq_attrs->{query_leftover}${order_group_having} |
6a6394f1 |
326 | ) $qalias |
327 | ) $qalias WHERE $idx_name BETWEEN ? AND ? |
d9672fb9 |
328 | EOS |
6a6394f1 |
329 | } |
330 | } |
7fca91be |
331 | |
6a6394f1 |
332 | # used by _Top and _FetchFirst below |
96eacdb7 |
333 | sub _prep_for_skimming_limit { |
334 | my ( $self, $sql, $rs_attrs ) = @_; |
7fca91be |
335 | |
7fca91be |
336 | # get selectors |
cecf64bc |
337 | my $sq_attrs = $self->_subqueried_limit_attrs ($sql, $rs_attrs); |
7fca91be |
338 | |
339 | my $requested_order = delete $rs_attrs->{order_by}; |
cecf64bc |
340 | $sq_attrs->{order_by_requested} = $self->_order_by ($requested_order); |
341 | $sq_attrs->{grpby_having} = $self->_parse_rs_attrs ($rs_attrs); |
7fca91be |
342 | |
a66b662c |
343 | # without an offset things are easy |
344 | if (! $rs_attrs->{offset}) { |
345 | $sq_attrs->{order_by_inner} = $sq_attrs->{order_by_requested}; |
86bb5a27 |
346 | } |
347 | else { |
a66b662c |
348 | $sq_attrs->{quoted_rs_alias} = $self->_quote ($rs_attrs->{alias}); |
349 | |
350 | # localise as we already have all the bind values we need |
351 | local $self->{order_bind}; |
352 | |
353 | # make up an order unless supplied or sanity check what we are given |
354 | my $inner_order; |
355 | if ($sq_attrs->{order_by_requested}) { |
356 | $self->throw_exception ( |
357 | 'Unable to safely perform "skimming type" limit with supplied unstable order criteria' |
5f11e54f |
358 | ) unless ($rs_attrs->{_rsroot_rsrc}->schema->storage->_order_by_is_stable( |
a66b662c |
359 | $rs_attrs->{from}, |
5f11e54f |
360 | $requested_order, |
361 | $rs_attrs->{where}, |
362 | )); |
7fca91be |
363 | |
a66b662c |
364 | $inner_order = $requested_order; |
365 | } |
366 | else { |
367 | $inner_order = [ map |
368 | { "$rs_attrs->{alias}.$_" } |
369 | ( @{ |
370 | $rs_attrs->{_rsroot_rsrc}->_identifying_column_set |
371 | || |
372 | $self->throw_exception(sprintf( |
373 | 'Unable to auto-construct stable order criteria for "skimming type" limit ' |
374 | . "dialect based on source '%s'", $rs_attrs->{_rsroot_rsrc}->name) ); |
375 | } ) |
376 | ]; |
377 | } |
7fca91be |
378 | |
a66b662c |
379 | $sq_attrs->{order_by_inner} = $self->_order_by ($inner_order); |
cecf64bc |
380 | |
a66b662c |
381 | my @out_chunks; |
382 | for my $ch ($self->_order_by_chunks ($inner_order)) { |
383 | $ch = $ch->[0] if ref $ch eq 'ARRAY'; |
7fca91be |
384 | |
cb3e87f5 |
385 | ($ch, my $is_desc) = $self->_split_order_chunk($ch); |
386 | |
387 | # !NOTE! outside chunks come in reverse order ( !$is_desc ) |
388 | push @out_chunks, { ($is_desc ? '-asc' : '-desc') => \$ch }; |
7fca91be |
389 | } |
390 | |
a66b662c |
391 | $sq_attrs->{order_by_middle} = $self->_order_by (\@out_chunks); |
392 | |
393 | # this is the order supplement magic |
394 | $sq_attrs->{selection_middle} = $sq_attrs->{selection_outer}; |
395 | if (my $extra_order_sel = $sq_attrs->{order_supplement}) { |
396 | for my $extra_col (sort |
397 | { $extra_order_sel->{$a} cmp $extra_order_sel->{$b} } |
398 | keys %$extra_order_sel |
399 | ) { |
400 | $sq_attrs->{selection_inner} .= sprintf (', %s AS %s', |
401 | $extra_col, |
402 | $extra_order_sel->{$extra_col}, |
403 | ); |
404 | |
405 | $sq_attrs->{selection_middle} .= ', ' . $extra_order_sel->{$extra_col}; |
406 | } |
407 | |
408 | # Whatever order bindvals there are, they will be realiased and |
409 | # reselected, and need to show up at end of the initial inner select |
410 | push @{$self->{select_bind}}, @{$self->{order_bind}}; |
cecf64bc |
411 | } |
86bb5a27 |
412 | |
a66b662c |
413 | # and this is order re-alias magic |
414 | for my $map ($sq_attrs->{order_supplement}, $sq_attrs->{outer_renames}) { |
833733fe |
415 | for my $col (sort { (length $b) <=> (length $a) } keys %{$map||{}}) { |
a66b662c |
416 | my $re_col = quotemeta ($col); |
417 | $_ =~ s/$re_col/$map->{$col}/ |
418 | for ($sq_attrs->{order_by_middle}, $sq_attrs->{order_by_requested}); |
419 | } |
7fca91be |
420 | } |
421 | } |
422 | |
cecf64bc |
423 | $sq_attrs; |
96eacdb7 |
424 | } |
425 | |
426 | =head2 Top |
427 | |
428 | SELECT * FROM |
429 | |
430 | SELECT TOP $limit FROM ( |
431 | SELECT TOP $limit FROM ( |
432 | SELECT TOP ($limit+$offset) ... |
433 | ) ORDER BY $reversed_original_order |
434 | ) ORDER BY $original_order |
435 | |
436 | Unreliable Top-based implementation, supported by B<< MSSQL < 2005 >>. |
437 | |
438 | =head3 CAVEAT |
439 | |
440 | Due to its implementation, this limit dialect returns B<incorrect results> |
441 | when $limit+$offset > total amount of rows in the resultset. |
442 | |
443 | =cut |
444 | |
445 | sub _Top { |
446 | my ( $self, $sql, $rs_attrs, $rows, $offset ) = @_; |
447 | |
cecf64bc |
448 | my $lim = $self->_prep_for_skimming_limit($sql, $rs_attrs); |
7fca91be |
449 | |
450 | $sql = sprintf ('SELECT TOP %u %s %s %s %s', |
451 | $rows + ($offset||0), |
a66b662c |
452 | $offset ? $lim->{selection_inner} : $lim->{selection_original}, |
cecf64bc |
453 | $lim->{query_leftover}, |
454 | $lim->{grpby_having}, |
455 | $lim->{order_by_inner}, |
7fca91be |
456 | ); |
457 | |
458 | $sql = sprintf ('SELECT TOP %u %s FROM ( %s ) %s %s', |
459 | $rows, |
cecf64bc |
460 | $lim->{selection_middle}, |
7fca91be |
461 | $sql, |
cecf64bc |
462 | $lim->{quoted_rs_alias}, |
463 | $lim->{order_by_middle}, |
7fca91be |
464 | ) if $offset; |
465 | |
1b07861d |
466 | $sql = sprintf ('SELECT %s FROM ( %s ) %s %s', |
cecf64bc |
467 | $lim->{selection_outer}, |
96eacdb7 |
468 | $sql, |
cecf64bc |
469 | $lim->{quoted_rs_alias}, |
470 | $lim->{order_by_requested}, |
471 | ) if $offset and ( |
472 | $lim->{order_by_requested} or $lim->{selection_middle} ne $lim->{selection_outer} |
473 | ); |
96eacdb7 |
474 | |
475 | return $sql; |
476 | } |
477 | |
478 | =head2 FetchFirst |
479 | |
480 | SELECT * FROM |
481 | ( |
482 | SELECT * FROM ( |
483 | SELECT * FROM ( |
484 | SELECT * FROM ... |
485 | ) ORDER BY $reversed_original_order |
486 | FETCH FIRST $limit ROWS ONLY |
487 | ) ORDER BY $original_order |
488 | FETCH FIRST $limit ROWS ONLY |
489 | ) |
490 | |
491 | Unreliable FetchFirst-based implementation, supported by B<< IBM DB2 <= V5R3 >>. |
492 | |
493 | =head3 CAVEAT |
494 | |
495 | Due to its implementation, this limit dialect returns B<incorrect results> |
496 | when $limit+$offset > total amount of rows in the resultset. |
497 | |
498 | =cut |
499 | |
500 | sub _FetchFirst { |
501 | my ( $self, $sql, $rs_attrs, $rows, $offset ) = @_; |
502 | |
cecf64bc |
503 | my $lim = $self->_prep_for_skimming_limit($sql, $rs_attrs); |
96eacdb7 |
504 | |
505 | $sql = sprintf ('SELECT %s %s %s %s FETCH FIRST %u ROWS ONLY', |
a66b662c |
506 | $offset ? $lim->{selection_inner} : $lim->{selection_original}, |
cecf64bc |
507 | $lim->{query_leftover}, |
508 | $lim->{grpby_having}, |
509 | $lim->{order_by_inner}, |
96eacdb7 |
510 | $rows + ($offset||0), |
511 | ); |
512 | |
513 | $sql = sprintf ('SELECT %s FROM ( %s ) %s %s FETCH FIRST %u ROWS ONLY', |
cecf64bc |
514 | $lim->{selection_middle}, |
96eacdb7 |
515 | $sql, |
cecf64bc |
516 | $lim->{quoted_rs_alias}, |
517 | $lim->{order_by_middle}, |
96eacdb7 |
518 | $rows, |
519 | ) if $offset; |
520 | |
cecf64bc |
521 | |
1b07861d |
522 | $sql = sprintf ('SELECT %s FROM ( %s ) %s %s', |
cecf64bc |
523 | $lim->{selection_outer}, |
7fca91be |
524 | $sql, |
cecf64bc |
525 | $lim->{quoted_rs_alias}, |
526 | $lim->{order_by_requested}, |
cecf64bc |
527 | ) if $offset and ( |
528 | $lim->{order_by_requested} or $lim->{selection_middle} ne $lim->{selection_outer} |
529 | ); |
7fca91be |
530 | |
7fca91be |
531 | return $sql; |
532 | } |
533 | |
d5dedbd6 |
534 | =head2 GenericSubQ |
535 | |
536 | SELECT * FROM ( |
537 | SELECT ... |
538 | ) |
539 | WHERE ( |
540 | SELECT COUNT(*) FROM $original_table cnt WHERE cnt.id < $original_table.id |
541 | ) BETWEEN $offset AND ($offset+$rows-1) |
542 | |
543 | This is the most evil limit "dialect" (more of a hack) for I<really> stupid |
544 | databases. It works by ordering the set by some unique column, and calculating |
545 | the amount of rows that have a less-er value (thus emulating a L</RowNum>-like |
546 | index). Of course this implies the set can only be ordered by a single unique |
038b8126 |
547 | column. |
548 | |
549 | Also note that this technique can be and often is B<excruciatingly slow>. You |
550 | may have much better luck using L<DBIx::Class::ResultSet/software_limit> |
551 | instead. |
d5dedbd6 |
552 | |
553 | Currently used by B<Sybase ASE>, due to lack of any other option. |
554 | |
555 | =cut |
7fca91be |
556 | sub _GenericSubQ { |
557 | my ($self, $sql, $rs_attrs, $rows, $offset) = @_; |
558 | |
4376a157 |
559 | my $root_rsrc = $rs_attrs->{_rsroot_rsrc}; |
7fca91be |
560 | |
318e3d94 |
561 | # Explicitly require an order_by |
562 | # GenSubQ is slow enough as it is, just emulating things |
563 | # like in other cases is not wise - make the user work |
564 | # to shoot their DBA in the foot |
565 | my $supplied_order = delete $rs_attrs->{order_by} or $self->throw_exception ( |
566 | 'Generic Subquery Limit does not work on resultsets without an order. Provide a stable, ' |
567 | . 'root-table-based order criteria.' |
568 | ); |
569 | |
570 | my $usable_order_ci = $root_rsrc->storage->_main_source_order_by_portion_is_stable( |
571 | $root_rsrc, |
572 | $supplied_order, |
573 | $rs_attrs->{where}, |
574 | ) or $self->throw_exception( |
575 | 'Generic Subquery Limit can not work with order criteria based on sources other than the current one' |
576 | ); |
577 | |
578 | ### |
579 | ### |
580 | ### we need to know the directions after we figured out the above - reextract *again* |
581 | ### this is eyebleed - trying to get it to work at first |
582 | my @order_bits = do { |
7fca91be |
583 | local $self->{quote_char}; |
2d841fdc |
584 | local $self->{order_bind}; |
318e3d94 |
585 | map { ref $_ ? $_->[0] : $_ } $self->_order_by_chunks ($supplied_order) |
586 | }; |
7fca91be |
587 | |
318e3d94 |
588 | # truncate to what we'll use |
589 | $#order_bits = ( (keys %$usable_order_ci) - 1 ); |
7fca91be |
590 | |
318e3d94 |
591 | # @order_bits likely will come back quoted (due to how the prefetch |
592 | # rewriter operates |
593 | # Hence supplement the column_info lookup table with quoted versions |
594 | if ($self->quote_char) { |
595 | $usable_order_ci->{$self->_quote($_)} = $usable_order_ci->{$_} |
596 | for keys %$usable_order_ci; |
597 | } |
7fca91be |
598 | |
318e3d94 |
599 | # calculate the condition |
600 | my $count_tbl_alias = 'rownum__emulation'; |
601 | my $root_alias = $rs_attrs->{alias}; |
602 | my $root_tbl_name = $root_rsrc->name; |
7fca91be |
603 | |
318e3d94 |
604 | my (@unqualified_names, @qualified_names, @is_desc, @new_order_by); |
7fca91be |
605 | |
318e3d94 |
606 | for my $bit (@order_bits) { |
7fca91be |
607 | |
cb3e87f5 |
608 | ($bit, my $is_desc) = $self->_split_order_chunk($bit); |
7fca91be |
609 | |
318e3d94 |
610 | push @is_desc, $is_desc; |
611 | push @unqualified_names, $usable_order_ci->{$bit}{-colname}; |
612 | push @qualified_names, $usable_order_ci->{$bit}{-fq_colname}; |
7fca91be |
613 | |
318e3d94 |
614 | push @new_order_by, { ($is_desc ? '-desc' : '-asc') => $usable_order_ci->{$bit}{-fq_colname} }; |
2d841fdc |
615 | }; |
7fca91be |
616 | |
318e3d94 |
617 | my (@where_cond, @skip_colpair_stack); |
618 | for my $i (0 .. $#order_bits) { |
619 | my $ci = $usable_order_ci->{$order_bits[$i]}; |
620 | |
621 | my ($subq_col, $main_col) = map { "$_.$ci->{-colname}" } ($count_tbl_alias, $root_alias); |
622 | my $cur_cond = { $subq_col => { ($is_desc[$i] ? '>' : '<') => { -ident => $main_col } } }; |
623 | |
624 | push @skip_colpair_stack, [ |
625 | { $main_col => { -ident => $subq_col } }, |
626 | ]; |
627 | |
628 | # we can trust the nullability flag because |
629 | # we already used it during _id_col_set resolution |
630 | # |
631 | if ($ci->{is_nullable}) { |
632 | push @{$skip_colpair_stack[-1]}, { $main_col => undef, $subq_col=> undef }; |
633 | |
634 | $cur_cond = [ |
635 | { |
636 | ($is_desc[$i] ? $subq_col : $main_col) => { '!=', undef }, |
637 | ($is_desc[$i] ? $main_col : $subq_col) => undef, |
638 | }, |
639 | { |
640 | $subq_col => { '!=', undef }, |
641 | $main_col => { '!=', undef }, |
642 | -and => $cur_cond, |
643 | }, |
644 | ]; |
645 | } |
cecf64bc |
646 | |
318e3d94 |
647 | push @where_cond, { '-and', => [ @skip_colpair_stack[0..$i-1], $cur_cond ] }; |
648 | } |
7fca91be |
649 | |
318e3d94 |
650 | # reuse the sqlmaker WHERE, this will not be returning binds |
651 | my $counted_where = do { |
652 | local $self->{where_bind}; |
653 | $self->where(\@where_cond); |
654 | }; |
655 | |
656 | # construct the rownum condition by hand |
69d3c270 |
657 | my $rownum_cond; |
658 | if ($offset) { |
659 | $rownum_cond = 'BETWEEN ? AND ?'; |
69d3c270 |
660 | push @{$self->{limit_bind}}, |
661 | [ $self->__offset_bindtype => $offset ], |
662 | [ $self->__total_bindtype => $offset + $rows - 1] |
663 | ; |
664 | } |
665 | else { |
666 | $rownum_cond = '< ?'; |
69d3c270 |
667 | push @{$self->{limit_bind}}, |
668 | [ $self->__rows_bindtype => $rows ] |
669 | ; |
670 | } |
671 | |
318e3d94 |
672 | # and what we will order by inside |
673 | my $inner_order_sql = do { |
674 | local $self->{order_bind}; |
675 | |
676 | my $s = $self->_order_by (\@new_order_by); |
677 | |
678 | $self->throw_exception('Inner gensubq order may not contain binds... something went wrong') |
679 | if @{$self->{order_bind}}; |
680 | |
681 | $s; |
682 | }; |
683 | |
684 | ### resume originally scheduled programming |
685 | ### |
686 | ### |
687 | |
688 | # we need to supply the order for the supplements to be properly calculated |
689 | my $sq_attrs = $self->_subqueried_limit_attrs ( |
690 | $sql, { %$rs_attrs, order_by => \@new_order_by } |
691 | ); |
692 | |
693 | my $in_sel = $sq_attrs->{selection_inner}; |
694 | |
695 | # add the order supplement (if any) as this is what will be used for the outer WHERE |
696 | $in_sel .= ", $_" for sort keys %{$sq_attrs->{order_supplement}}; |
697 | |
698 | my $group_having_sql = $self->_parse_rs_attrs($rs_attrs); |
699 | |
2d841fdc |
700 | |
69d3c270 |
701 | return sprintf (" |
cecf64bc |
702 | SELECT $sq_attrs->{selection_outer} |
7fca91be |
703 | FROM ( |
cecf64bc |
704 | SELECT $in_sel $sq_attrs->{query_leftover}${group_having_sql} |
7fca91be |
705 | ) %s |
318e3d94 |
706 | WHERE ( SELECT COUNT(*) FROM %s %s $counted_where ) $rownum_cond |
707 | $inner_order_sql |
69d3c270 |
708 | ", map { $self->_quote ($_) } ( |
709 | $rs_attrs->{alias}, |
710 | $root_tbl_name, |
711 | $count_tbl_alias, |
69d3c270 |
712 | )); |
7fca91be |
713 | } |
714 | |
715 | |
716 | # !!! THIS IS ALSO HORRIFIC !!! /me ashamed |
717 | # |
718 | # Generates inner/outer select lists for various limit dialects |
719 | # which result in one or more subqueries (e.g. RNO, Top, RowNum) |
720 | # Any non-root-table columns need to have their table qualifier |
721 | # turned into a column alias (otherwise names in subqueries clash |
722 | # and/or lose their source table) |
723 | # |
69d3c270 |
724 | # Returns mangled proto-sql, inner/outer strings of SQL QUOTED selectors |
725 | # with aliases (to be used in whatever select statement), and an alias |
8273e845 |
726 | # index hashref of QUOTED SEL => QUOTED ALIAS pairs (to maybe be used |
69d3c270 |
727 | # for string-subst higher up). |
7fca91be |
728 | # If an order_by is supplied, the inner select needs to bring out columns |
729 | # used in implicit (non-selected) orders, and the order condition itself |
730 | # needs to be realiased to the proper names in the outer query. Thus we |
731 | # also return a hashref (order doesn't matter) of QUOTED EXTRA-SEL => |
732 | # QUOTED ALIAS pairs, which is a list of extra selectors that do *not* |
733 | # exist in the original select list |
7fca91be |
734 | sub _subqueried_limit_attrs { |
69d3c270 |
735 | my ($self, $proto_sql, $rs_attrs) = @_; |
7fca91be |
736 | |
70c28808 |
737 | $self->throw_exception( |
738 | 'Limit dialect implementation usable only in the context of DBIC (missing $rs_attrs)' |
739 | ) unless ref ($rs_attrs) eq 'HASH'; |
7fca91be |
740 | |
f74d22e2 |
741 | # mangle the input sql as we will be replacing the selector entirely |
742 | unless ( |
743 | $rs_attrs->{_selector_sql} |
744 | and |
745 | $proto_sql =~ s/^ \s* SELECT \s* \Q$rs_attrs->{_selector_sql}//ix |
746 | ) { |
747 | $self->throw_exception("Unrecognizable SELECT: $proto_sql"); |
748 | } |
69d3c270 |
749 | |
3f5b99fe |
750 | my ($re_sep, $re_alias) = map { quotemeta $_ } ( $self->{name_sep}, $rs_attrs->{alias} ); |
7fca91be |
751 | |
752 | # correlate select and as, build selection index |
753 | my (@sel, $in_sel_index); |
754 | for my $i (0 .. $#{$rs_attrs->{select}}) { |
755 | |
756 | my $s = $rs_attrs->{select}[$i]; |
7fca91be |
757 | my $sql_alias = (ref $s) eq 'HASH' ? $s->{-as} : undef; |
758 | |
ad1d374e |
759 | # we throw away the @bind here deliberately |
760 | my ($sql_sel) = $self->_recurse_fields ($s); |
761 | |
7fca91be |
762 | push @sel, { |
90ed89cb |
763 | arg => $s, |
7fca91be |
764 | sql => $sql_sel, |
69d3c270 |
765 | unquoted_sql => do { |
766 | local $self->{quote_char}; |
ad1d374e |
767 | ($self->_recurse_fields ($s))[0]; # ignore binds again |
69d3c270 |
768 | }, |
7fca91be |
769 | as => |
770 | $sql_alias |
771 | || |
772 | $rs_attrs->{as}[$i] |
773 | || |
70c28808 |
774 | $self->throw_exception("Select argument $i ($s) without corresponding 'as'") |
7fca91be |
775 | , |
776 | }; |
777 | |
f1be7448 |
778 | # anything with a placeholder in it needs re-selection |
779 | $in_sel_index->{$sql_sel}++ unless $sql_sel =~ / (?: ^ | \W ) \? (?: \W | $ ) /x; |
780 | |
7fca91be |
781 | $in_sel_index->{$self->_quote ($sql_alias)}++ if $sql_alias; |
782 | |
783 | # record unqualified versions too, so we do not have |
784 | # to reselect the same column twice (in qualified and |
785 | # unqualified form) |
786 | if (! ref $s && $sql_sel =~ / $re_sep (.+) $/x) { |
787 | $in_sel_index->{$1}++; |
788 | } |
789 | } |
790 | |
791 | |
792 | # re-alias and remove any name separators from aliases, |
793 | # unless we are dealing with the current source alias |
794 | # (which will transcend the subqueries as it is necessary |
795 | # for possible further chaining) |
4d45ab4b |
796 | # same for anything we do not recognize |
cecf64bc |
797 | my ($sel, $renamed); |
7fca91be |
798 | for my $node (@sel) { |
a66b662c |
799 | push @{$sel->{original}}, $node->{sql}; |
800 | |
3f5b99fe |
801 | if ( |
4d45ab4b |
802 | ! $in_sel_index->{$node->{sql}} |
803 | or |
3f5b99fe |
804 | $node->{as} =~ / (?<! ^ $re_alias ) \. /x |
805 | or |
806 | $node->{unquoted_sql} =~ / (?<! ^ $re_alias ) $re_sep /x |
807 | ) { |
7fca91be |
808 | $node->{as} = $self->_unqualify_colname($node->{as}); |
809 | my $quoted_as = $self->_quote($node->{as}); |
cecf64bc |
810 | push @{$sel->{inner}}, sprintf '%s AS %s', $node->{sql}, $quoted_as; |
811 | push @{$sel->{outer}}, $quoted_as; |
812 | $renamed->{$node->{sql}} = $quoted_as; |
7fca91be |
813 | } |
814 | else { |
cecf64bc |
815 | push @{$sel->{inner}}, $node->{sql}; |
90ed89cb |
816 | push @{$sel->{outer}}, $self->_quote (ref $node->{arg} ? $node->{as} : $node->{arg}); |
7fca91be |
817 | } |
818 | } |
cecf64bc |
819 | |
7fca91be |
820 | # see if the order gives us anything |
cecf64bc |
821 | my $extra_order_sel; |
7fca91be |
822 | for my $chunk ($self->_order_by_chunks ($rs_attrs->{order_by})) { |
823 | # order with bind |
824 | $chunk = $chunk->[0] if (ref $chunk) eq 'ARRAY'; |
cb3e87f5 |
825 | ($chunk) = $self->_split_order_chunk($chunk); |
7fca91be |
826 | |
827 | next if $in_sel_index->{$chunk}; |
828 | |
cecf64bc |
829 | $extra_order_sel->{$chunk} ||= $self->_quote ( |
08a1eaad |
830 | 'ORDER__BY__' . sprintf '%03d', scalar keys %{$extra_order_sel||{}} |
7fca91be |
831 | ); |
832 | } |
833 | |
cecf64bc |
834 | return { |
835 | query_leftover => $proto_sql, |
836 | (map {( "selection_$_" => join (', ', @{$sel->{$_}} ) )} keys %$sel ), |
837 | outer_renames => $renamed, |
838 | order_supplement => $extra_order_sel, |
839 | }; |
7fca91be |
840 | } |
841 | |
842 | sub _unqualify_colname { |
843 | my ($self, $fqcn) = @_; |
3f5b99fe |
844 | $fqcn =~ s/ \. /__/xg; |
7fca91be |
845 | return $fqcn; |
846 | } |
847 | |
848 | 1; |
d5dedbd6 |
849 | |
850 | =head1 AUTHORS |
851 | |
852 | See L<DBIx::Class/CONTRIBUTORS>. |
853 | |
854 | =head1 LICENSE |
855 | |
856 | You may distribute this code under the same terms as Perl itself. |
857 | |
858 | =cut |