Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * heaptoast.c
4 : * Heap-specific definitions for external and compressed storage
5 : * of variable size attributes.
6 : *
7 : * Copyright (c) 2000-2025, PostgreSQL Global Development Group
8 : *
9 : *
10 : * IDENTIFICATION
11 : * src/backend/access/heap/heaptoast.c
12 : *
13 : *
14 : * INTERFACE ROUTINES
15 : * heap_toast_insert_or_update -
16 : * Try to make a given tuple fit into one page by compressing
17 : * or moving off attributes
18 : *
19 : * heap_toast_delete -
20 : * Reclaim toast storage when a tuple is deleted
21 : *
22 : *-------------------------------------------------------------------------
23 : */
24 :
25 : #include "postgres.h"
26 :
27 : #include "access/detoast.h"
28 : #include "access/genam.h"
29 : #include "access/heapam.h"
30 : #include "access/heaptoast.h"
31 : #include "access/toast_helper.h"
32 : #include "access/toast_internals.h"
33 : #include "utils/fmgroids.h"
34 :
35 :
36 : /* ----------
37 : * heap_toast_delete -
38 : *
39 : * Cascaded delete toast-entries on DELETE
40 : * ----------
41 : */
42 : void
43 580 : heap_toast_delete(Relation rel, HeapTuple oldtup, bool is_speculative)
44 : {
45 : TupleDesc tupleDesc;
46 : Datum toast_values[MaxHeapAttributeNumber];
47 : bool toast_isnull[MaxHeapAttributeNumber];
48 :
49 : /*
50 : * We should only ever be called for tuples of plain relations or
51 : * materialized views --- recursing on a toast rel is bad news.
52 : */
53 : Assert(rel->rd_rel->relkind == RELKIND_RELATION ||
54 : rel->rd_rel->relkind == RELKIND_MATVIEW);
55 :
56 : /*
57 : * Get the tuple descriptor and break down the tuple into fields.
58 : *
59 : * NOTE: it's debatable whether to use heap_deform_tuple() here or just
60 : * heap_getattr() only the varlena columns. The latter could win if there
61 : * are few varlena columns and many non-varlena ones. However,
62 : * heap_deform_tuple costs only O(N) while the heap_getattr way would cost
63 : * O(N^2) if there are many varlena columns, so it seems better to err on
64 : * the side of linear cost. (We won't even be here unless there's at
65 : * least one varlena column, by the way.)
66 : */
67 580 : tupleDesc = rel->rd_att;
68 :
69 : Assert(tupleDesc->natts <= MaxHeapAttributeNumber);
70 580 : heap_deform_tuple(oldtup, tupleDesc, toast_values, toast_isnull);
71 :
72 : /* Do the real work. */
73 580 : toast_delete_external(rel, toast_values, toast_isnull, is_speculative);
74 580 : }
75 :
76 :
77 : /* ----------
78 : * heap_toast_insert_or_update -
79 : *
80 : * Delete no-longer-used toast-entries and create new ones to
81 : * make the new tuple fit on INSERT or UPDATE
82 : *
83 : * Inputs:
84 : * newtup: the candidate new tuple to be inserted
85 : * oldtup: the old row version for UPDATE, or NULL for INSERT
86 : * options: options to be passed to heap_insert() for toast rows
87 : * Result:
88 : * either newtup if no toasting is needed, or a palloc'd modified tuple
89 : * that is what should actually get stored
90 : *
91 : * NOTE: neither newtup nor oldtup will be modified. This is a change
92 : * from the pre-8.1 API of this routine.
93 : * ----------
94 : */
95 : HeapTuple
96 37116 : heap_toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup,
97 : int options)
98 : {
99 : HeapTuple result_tuple;
100 : TupleDesc tupleDesc;
101 : int numAttrs;
102 :
103 : Size maxDataLen;
104 : Size hoff;
105 :
106 : bool toast_isnull[MaxHeapAttributeNumber];
107 : bool toast_oldisnull[MaxHeapAttributeNumber];
108 : Datum toast_values[MaxHeapAttributeNumber];
109 : Datum toast_oldvalues[MaxHeapAttributeNumber];
110 : ToastAttrInfo toast_attr[MaxHeapAttributeNumber];
111 : ToastTupleContext ttc;
112 :
113 : /*
114 : * Ignore the INSERT_SPECULATIVE option. Speculative insertions/super
115 : * deletions just normally insert/delete the toast values. It seems
116 : * easiest to deal with that here, instead on, potentially, multiple
117 : * callers.
118 : */
119 37116 : options &= ~HEAP_INSERT_SPECULATIVE;
120 :
121 : /*
122 : * We should only ever be called for tuples of plain relations or
123 : * materialized views --- recursing on a toast rel is bad news.
124 : */
125 : Assert(rel->rd_rel->relkind == RELKIND_RELATION ||
126 : rel->rd_rel->relkind == RELKIND_MATVIEW);
127 :
128 : /*
129 : * Get the tuple descriptor and break down the tuple(s) into fields.
130 : */
131 37116 : tupleDesc = rel->rd_att;
132 37116 : numAttrs = tupleDesc->natts;
133 :
134 : Assert(numAttrs <= MaxHeapAttributeNumber);
135 37116 : heap_deform_tuple(newtup, tupleDesc, toast_values, toast_isnull);
136 37116 : if (oldtup != NULL)
137 2646 : heap_deform_tuple(oldtup, tupleDesc, toast_oldvalues, toast_oldisnull);
138 :
139 : /* ----------
140 : * Prepare for toasting
141 : * ----------
142 : */
143 37116 : ttc.ttc_rel = rel;
144 37116 : ttc.ttc_values = toast_values;
145 37116 : ttc.ttc_isnull = toast_isnull;
146 37116 : if (oldtup == NULL)
147 : {
148 34470 : ttc.ttc_oldvalues = NULL;
149 34470 : ttc.ttc_oldisnull = NULL;
150 : }
151 : else
152 : {
153 2646 : ttc.ttc_oldvalues = toast_oldvalues;
154 2646 : ttc.ttc_oldisnull = toast_oldisnull;
155 : }
156 37116 : ttc.ttc_attr = toast_attr;
157 37116 : toast_tuple_init(&ttc);
158 :
159 : /* ----------
160 : * Compress and/or save external until data fits into target length
161 : *
162 : * 1: Inline compress attributes with attstorage EXTENDED, and store very
163 : * large attributes with attstorage EXTENDED or EXTERNAL external
164 : * immediately
165 : * 2: Store attributes with attstorage EXTENDED or EXTERNAL external
166 : * 3: Inline compress attributes with attstorage MAIN
167 : * 4: Store attributes with attstorage MAIN external
168 : * ----------
169 : */
170 :
171 : /* compute header overhead --- this should match heap_form_tuple() */
172 37116 : hoff = SizeofHeapTupleHeader;
173 37116 : if ((ttc.ttc_flags & TOAST_HAS_NULLS) != 0)
174 5216 : hoff += BITMAPLEN(numAttrs);
175 37116 : hoff = MAXALIGN(hoff);
176 : /* now convert to a limit on the tuple data size */
177 37116 : maxDataLen = RelationGetToastTupleTarget(rel, TOAST_TUPLE_TARGET) - hoff;
178 :
179 : /*
180 : * Look for attributes with attstorage EXTENDED to compress. Also find
181 : * large attributes with attstorage EXTENDED or EXTERNAL, and store them
182 : * external.
183 : */
184 77068 : while (heap_compute_data_size(tupleDesc,
185 : toast_values, toast_isnull) > maxDataLen)
186 : {
187 : int biggest_attno;
188 :
189 41358 : biggest_attno = toast_tuple_find_biggest_attribute(&ttc, true, false);
190 41358 : if (biggest_attno < 0)
191 1406 : break;
192 :
193 : /*
194 : * Attempt to compress it inline, if it has attstorage EXTENDED
195 : */
196 39952 : if (TupleDescAttr(tupleDesc, biggest_attno)->attstorage == TYPSTORAGE_EXTENDED)
197 34154 : toast_tuple_try_compression(&ttc, biggest_attno);
198 : else
199 : {
200 : /*
201 : * has attstorage EXTERNAL, ignore on subsequent compression
202 : * passes
203 : */
204 5798 : toast_attr[biggest_attno].tai_colflags |= TOASTCOL_INCOMPRESSIBLE;
205 : }
206 :
207 : /*
208 : * If this value is by itself more than maxDataLen (after compression
209 : * if any), push it out to the toast table immediately, if possible.
210 : * This avoids uselessly compressing other fields in the common case
211 : * where we have one long field and several short ones.
212 : *
213 : * XXX maybe the threshold should be less than maxDataLen?
214 : */
215 39952 : if (toast_attr[biggest_attno].tai_size > maxDataLen &&
216 13954 : rel->rd_rel->reltoastrelid != InvalidOid)
217 13954 : toast_tuple_externalize(&ttc, biggest_attno, options);
218 : }
219 :
220 : /*
221 : * Second we look for attributes of attstorage EXTENDED or EXTERNAL that
222 : * are still inline, and make them external. But skip this if there's no
223 : * toast table to push them to.
224 : */
225 38498 : while (heap_compute_data_size(tupleDesc,
226 1448 : toast_values, toast_isnull) > maxDataLen &&
227 1448 : rel->rd_rel->reltoastrelid != InvalidOid)
228 : {
229 : int biggest_attno;
230 :
231 1436 : biggest_attno = toast_tuple_find_biggest_attribute(&ttc, false, false);
232 1436 : if (biggest_attno < 0)
233 54 : break;
234 1382 : toast_tuple_externalize(&ttc, biggest_attno, options);
235 : }
236 :
237 : /*
238 : * Round 3 - this time we take attributes with storage MAIN into
239 : * compression
240 : */
241 37158 : while (heap_compute_data_size(tupleDesc,
242 : toast_values, toast_isnull) > maxDataLen)
243 : {
244 : int biggest_attno;
245 :
246 66 : biggest_attno = toast_tuple_find_biggest_attribute(&ttc, true, true);
247 66 : if (biggest_attno < 0)
248 24 : break;
249 :
250 42 : toast_tuple_try_compression(&ttc, biggest_attno);
251 : }
252 :
253 : /*
254 : * Finally we store attributes of type MAIN externally. At this point we
255 : * increase the target tuple size, so that MAIN attributes aren't stored
256 : * externally unless really necessary.
257 : */
258 37116 : maxDataLen = TOAST_TUPLE_TARGET_MAIN - hoff;
259 :
260 37116 : while (heap_compute_data_size(tupleDesc,
261 0 : toast_values, toast_isnull) > maxDataLen &&
262 0 : rel->rd_rel->reltoastrelid != InvalidOid)
263 : {
264 : int biggest_attno;
265 :
266 0 : biggest_attno = toast_tuple_find_biggest_attribute(&ttc, false, true);
267 0 : if (biggest_attno < 0)
268 0 : break;
269 :
270 0 : toast_tuple_externalize(&ttc, biggest_attno, options);
271 : }
272 :
273 : /*
274 : * In the case we toasted any values, we need to build a new heap tuple
275 : * with the changed values.
276 : */
277 37116 : if ((ttc.ttc_flags & TOAST_NEEDS_CHANGE) != 0)
278 : {
279 36974 : HeapTupleHeader olddata = newtup->t_data;
280 : HeapTupleHeader new_data;
281 : int32 new_header_len;
282 : int32 new_data_len;
283 : int32 new_tuple_len;
284 :
285 : /*
286 : * Calculate the new size of the tuple.
287 : *
288 : * Note: we used to assume here that the old tuple's t_hoff must equal
289 : * the new_header_len value, but that was incorrect. The old tuple
290 : * might have a smaller-than-current natts, if there's been an ALTER
291 : * TABLE ADD COLUMN since it was stored; and that would lead to a
292 : * different conclusion about the size of the null bitmap, or even
293 : * whether there needs to be one at all.
294 : */
295 36974 : new_header_len = SizeofHeapTupleHeader;
296 36974 : if ((ttc.ttc_flags & TOAST_HAS_NULLS) != 0)
297 5150 : new_header_len += BITMAPLEN(numAttrs);
298 36974 : new_header_len = MAXALIGN(new_header_len);
299 36974 : new_data_len = heap_compute_data_size(tupleDesc,
300 : toast_values, toast_isnull);
301 36974 : new_tuple_len = new_header_len + new_data_len;
302 :
303 : /*
304 : * Allocate and zero the space needed, and fill HeapTupleData fields.
305 : */
306 36974 : result_tuple = (HeapTuple) palloc0(HEAPTUPLESIZE + new_tuple_len);
307 36974 : result_tuple->t_len = new_tuple_len;
308 36974 : result_tuple->t_self = newtup->t_self;
309 36974 : result_tuple->t_tableOid = newtup->t_tableOid;
310 36974 : new_data = (HeapTupleHeader) ((char *) result_tuple + HEAPTUPLESIZE);
311 36974 : result_tuple->t_data = new_data;
312 :
313 : /*
314 : * Copy the existing tuple header, but adjust natts and t_hoff.
315 : */
316 36974 : memcpy(new_data, olddata, SizeofHeapTupleHeader);
317 36974 : HeapTupleHeaderSetNatts(new_data, numAttrs);
318 36974 : new_data->t_hoff = new_header_len;
319 :
320 : /* Copy over the data, and fill the null bitmap if needed */
321 36974 : heap_fill_tuple(tupleDesc,
322 : toast_values,
323 : toast_isnull,
324 : (char *) new_data + new_header_len,
325 : new_data_len,
326 : &(new_data->t_infomask),
327 36974 : ((ttc.ttc_flags & TOAST_HAS_NULLS) != 0) ?
328 : new_data->t_bits : NULL);
329 : }
330 : else
331 142 : result_tuple = newtup;
332 :
333 37116 : toast_tuple_cleanup(&ttc);
334 :
335 37116 : return result_tuple;
336 : }
337 :
338 :
339 : /* ----------
340 : * toast_flatten_tuple -
341 : *
342 : * "Flatten" a tuple to contain no out-of-line toasted fields.
343 : * (This does not eliminate compressed or short-header datums.)
344 : *
345 : * Note: we expect the caller already checked HeapTupleHasExternal(tup),
346 : * so there is no need for a short-circuit path.
347 : * ----------
348 : */
349 : HeapTuple
350 3490 : toast_flatten_tuple(HeapTuple tup, TupleDesc tupleDesc)
351 : {
352 : HeapTuple new_tuple;
353 3490 : int numAttrs = tupleDesc->natts;
354 : int i;
355 : Datum toast_values[MaxTupleAttributeNumber];
356 : bool toast_isnull[MaxTupleAttributeNumber];
357 : bool toast_free[MaxTupleAttributeNumber];
358 :
359 : /*
360 : * Break down the tuple into fields.
361 : */
362 : Assert(numAttrs <= MaxTupleAttributeNumber);
363 3490 : heap_deform_tuple(tup, tupleDesc, toast_values, toast_isnull);
364 :
365 3490 : memset(toast_free, 0, numAttrs * sizeof(bool));
366 :
367 108910 : for (i = 0; i < numAttrs; i++)
368 : {
369 : /*
370 : * Look at non-null varlena attributes
371 : */
372 105420 : if (!toast_isnull[i] && TupleDescCompactAttr(tupleDesc, i)->attlen == -1)
373 : {
374 : struct varlena *new_value;
375 :
376 14730 : new_value = (struct varlena *) DatumGetPointer(toast_values[i]);
377 14730 : if (VARATT_IS_EXTERNAL(new_value))
378 : {
379 3568 : new_value = detoast_external_attr(new_value);
380 3568 : toast_values[i] = PointerGetDatum(new_value);
381 3568 : toast_free[i] = true;
382 : }
383 : }
384 : }
385 :
386 : /*
387 : * Form the reconfigured tuple.
388 : */
389 3490 : new_tuple = heap_form_tuple(tupleDesc, toast_values, toast_isnull);
390 :
391 : /*
392 : * Be sure to copy the tuple's identity fields. We also make a point of
393 : * copying visibility info, just in case anybody looks at those fields in
394 : * a syscache entry.
395 : */
396 3490 : new_tuple->t_self = tup->t_self;
397 3490 : new_tuple->t_tableOid = tup->t_tableOid;
398 :
399 3490 : new_tuple->t_data->t_choice = tup->t_data->t_choice;
400 3490 : new_tuple->t_data->t_ctid = tup->t_data->t_ctid;
401 3490 : new_tuple->t_data->t_infomask &= ~HEAP_XACT_MASK;
402 3490 : new_tuple->t_data->t_infomask |=
403 3490 : tup->t_data->t_infomask & HEAP_XACT_MASK;
404 3490 : new_tuple->t_data->t_infomask2 &= ~HEAP2_XACT_MASK;
405 3490 : new_tuple->t_data->t_infomask2 |=
406 3490 : tup->t_data->t_infomask2 & HEAP2_XACT_MASK;
407 :
408 : /*
409 : * Free allocated temp values
410 : */
411 108910 : for (i = 0; i < numAttrs; i++)
412 105420 : if (toast_free[i])
413 3568 : pfree(DatumGetPointer(toast_values[i]));
414 :
415 3490 : return new_tuple;
416 : }
417 :
418 :
419 : /* ----------
420 : * toast_flatten_tuple_to_datum -
421 : *
422 : * "Flatten" a tuple containing out-of-line toasted fields into a Datum.
423 : * The result is always palloc'd in the current memory context.
424 : *
425 : * We have a general rule that Datums of container types (rows, arrays,
426 : * ranges, etc) must not contain any external TOAST pointers. Without
427 : * this rule, we'd have to look inside each Datum when preparing a tuple
428 : * for storage, which would be expensive and would fail to extend cleanly
429 : * to new sorts of container types.
430 : *
431 : * However, we don't want to say that tuples represented as HeapTuples
432 : * can't contain toasted fields, so instead this routine should be called
433 : * when such a HeapTuple is being converted into a Datum.
434 : *
435 : * While we're at it, we decompress any compressed fields too. This is not
436 : * necessary for correctness, but reflects an expectation that compression
437 : * will be more effective if applied to the whole tuple not individual
438 : * fields. We are not so concerned about that that we want to deconstruct
439 : * and reconstruct tuples just to get rid of compressed fields, however.
440 : * So callers typically won't call this unless they see that the tuple has
441 : * at least one external field.
442 : *
443 : * On the other hand, in-line short-header varlena fields are left alone.
444 : * If we "untoasted" them here, they'd just get changed back to short-header
445 : * format anyway within heap_fill_tuple.
446 : * ----------
447 : */
448 : Datum
449 12 : toast_flatten_tuple_to_datum(HeapTupleHeader tup,
450 : uint32 tup_len,
451 : TupleDesc tupleDesc)
452 : {
453 : HeapTupleHeader new_data;
454 : int32 new_header_len;
455 : int32 new_data_len;
456 : int32 new_tuple_len;
457 : HeapTupleData tmptup;
458 12 : int numAttrs = tupleDesc->natts;
459 : int i;
460 12 : bool has_nulls = false;
461 : Datum toast_values[MaxTupleAttributeNumber];
462 : bool toast_isnull[MaxTupleAttributeNumber];
463 : bool toast_free[MaxTupleAttributeNumber];
464 :
465 : /* Build a temporary HeapTuple control structure */
466 12 : tmptup.t_len = tup_len;
467 12 : ItemPointerSetInvalid(&(tmptup.t_self));
468 12 : tmptup.t_tableOid = InvalidOid;
469 12 : tmptup.t_data = tup;
470 :
471 : /*
472 : * Break down the tuple into fields.
473 : */
474 : Assert(numAttrs <= MaxTupleAttributeNumber);
475 12 : heap_deform_tuple(&tmptup, tupleDesc, toast_values, toast_isnull);
476 :
477 12 : memset(toast_free, 0, numAttrs * sizeof(bool));
478 :
479 42 : for (i = 0; i < numAttrs; i++)
480 : {
481 : /*
482 : * Look at non-null varlena attributes
483 : */
484 30 : if (toast_isnull[i])
485 6 : has_nulls = true;
486 24 : else if (TupleDescCompactAttr(tupleDesc, i)->attlen == -1)
487 : {
488 : struct varlena *new_value;
489 :
490 24 : new_value = (struct varlena *) DatumGetPointer(toast_values[i]);
491 24 : if (VARATT_IS_EXTERNAL(new_value) ||
492 6 : VARATT_IS_COMPRESSED(new_value))
493 : {
494 18 : new_value = detoast_attr(new_value);
495 18 : toast_values[i] = PointerGetDatum(new_value);
496 18 : toast_free[i] = true;
497 : }
498 : }
499 : }
500 :
501 : /*
502 : * Calculate the new size of the tuple.
503 : *
504 : * This should match the reconstruction code in
505 : * heap_toast_insert_or_update.
506 : */
507 12 : new_header_len = SizeofHeapTupleHeader;
508 12 : if (has_nulls)
509 6 : new_header_len += BITMAPLEN(numAttrs);
510 12 : new_header_len = MAXALIGN(new_header_len);
511 12 : new_data_len = heap_compute_data_size(tupleDesc,
512 : toast_values, toast_isnull);
513 12 : new_tuple_len = new_header_len + new_data_len;
514 :
515 12 : new_data = (HeapTupleHeader) palloc0(new_tuple_len);
516 :
517 : /*
518 : * Copy the existing tuple header, but adjust natts and t_hoff.
519 : */
520 12 : memcpy(new_data, tup, SizeofHeapTupleHeader);
521 12 : HeapTupleHeaderSetNatts(new_data, numAttrs);
522 12 : new_data->t_hoff = new_header_len;
523 :
524 : /* Set the composite-Datum header fields correctly */
525 12 : HeapTupleHeaderSetDatumLength(new_data, new_tuple_len);
526 12 : HeapTupleHeaderSetTypeId(new_data, tupleDesc->tdtypeid);
527 12 : HeapTupleHeaderSetTypMod(new_data, tupleDesc->tdtypmod);
528 :
529 : /* Copy over the data, and fill the null bitmap if needed */
530 12 : heap_fill_tuple(tupleDesc,
531 : toast_values,
532 : toast_isnull,
533 : (char *) new_data + new_header_len,
534 : new_data_len,
535 : &(new_data->t_infomask),
536 : has_nulls ? new_data->t_bits : NULL);
537 :
538 : /*
539 : * Free allocated temp values
540 : */
541 42 : for (i = 0; i < numAttrs; i++)
542 30 : if (toast_free[i])
543 18 : pfree(DatumGetPointer(toast_values[i]));
544 :
545 12 : return PointerGetDatum(new_data);
546 : }
547 :
548 :
549 : /* ----------
550 : * toast_build_flattened_tuple -
551 : *
552 : * Build a tuple containing no out-of-line toasted fields.
553 : * (This does not eliminate compressed or short-header datums.)
554 : *
555 : * This is essentially just like heap_form_tuple, except that it will
556 : * expand any external-data pointers beforehand.
557 : *
558 : * It's not very clear whether it would be preferable to decompress
559 : * in-line compressed datums while at it. For now, we don't.
560 : * ----------
561 : */
562 : HeapTuple
563 46064 : toast_build_flattened_tuple(TupleDesc tupleDesc,
564 : Datum *values,
565 : bool *isnull)
566 : {
567 : HeapTuple new_tuple;
568 46064 : int numAttrs = tupleDesc->natts;
569 : int num_to_free;
570 : int i;
571 : Datum new_values[MaxTupleAttributeNumber];
572 : Pointer freeable_values[MaxTupleAttributeNumber];
573 :
574 : /*
575 : * We can pass the caller's isnull array directly to heap_form_tuple, but
576 : * we potentially need to modify the values array.
577 : */
578 : Assert(numAttrs <= MaxTupleAttributeNumber);
579 46064 : memcpy(new_values, values, numAttrs * sizeof(Datum));
580 :
581 46064 : num_to_free = 0;
582 260496 : for (i = 0; i < numAttrs; i++)
583 : {
584 : /*
585 : * Look at non-null varlena attributes
586 : */
587 214432 : if (!isnull[i] && TupleDescCompactAttr(tupleDesc, i)->attlen == -1)
588 : {
589 : struct varlena *new_value;
590 :
591 76360 : new_value = (struct varlena *) DatumGetPointer(new_values[i]);
592 76360 : if (VARATT_IS_EXTERNAL(new_value))
593 : {
594 402 : new_value = detoast_external_attr(new_value);
595 402 : new_values[i] = PointerGetDatum(new_value);
596 402 : freeable_values[num_to_free++] = (Pointer) new_value;
597 : }
598 : }
599 : }
600 :
601 : /*
602 : * Form the reconfigured tuple.
603 : */
604 46064 : new_tuple = heap_form_tuple(tupleDesc, new_values, isnull);
605 :
606 : /*
607 : * Free allocated temp values
608 : */
609 46466 : for (i = 0; i < num_to_free; i++)
610 402 : pfree(freeable_values[i]);
611 :
612 46064 : return new_tuple;
613 : }
614 :
615 : /*
616 : * Fetch a TOAST slice from a heap table.
617 : *
618 : * toastrel is the relation from which chunks are to be fetched.
619 : * valueid identifies the TOAST value from which chunks are being fetched.
620 : * attrsize is the total size of the TOAST value.
621 : * sliceoffset is the byte offset within the TOAST value from which to fetch.
622 : * slicelength is the number of bytes to be fetched from the TOAST value.
623 : * result is the varlena into which the results should be written.
624 : */
625 : void
626 20140 : heap_fetch_toast_slice(Relation toastrel, Oid valueid, int32 attrsize,
627 : int32 sliceoffset, int32 slicelength,
628 : struct varlena *result)
629 : {
630 : Relation *toastidxs;
631 : ScanKeyData toastkey[3];
632 20140 : TupleDesc toasttupDesc = toastrel->rd_att;
633 : int nscankeys;
634 : SysScanDesc toastscan;
635 : HeapTuple ttup;
636 : int32 expectedchunk;
637 20140 : int32 totalchunks = ((attrsize - 1) / TOAST_MAX_CHUNK_SIZE) + 1;
638 : int startchunk;
639 : int endchunk;
640 : int num_indexes;
641 : int validIndex;
642 :
643 : /* Look for the valid index of toast relation */
644 20140 : validIndex = toast_open_indexes(toastrel,
645 : AccessShareLock,
646 : &toastidxs,
647 : &num_indexes);
648 :
649 20140 : startchunk = sliceoffset / TOAST_MAX_CHUNK_SIZE;
650 20140 : endchunk = (sliceoffset + slicelength - 1) / TOAST_MAX_CHUNK_SIZE;
651 : Assert(endchunk <= totalchunks);
652 :
653 : /* Set up a scan key to fetch from the index. */
654 20140 : ScanKeyInit(&toastkey[0],
655 : (AttrNumber) 1,
656 : BTEqualStrategyNumber, F_OIDEQ,
657 : ObjectIdGetDatum(valueid));
658 :
659 : /*
660 : * No additional condition if fetching all chunks. Otherwise, use an
661 : * equality condition for one chunk, and a range condition otherwise.
662 : */
663 20140 : if (startchunk == 0 && endchunk == totalchunks - 1)
664 19864 : nscankeys = 1;
665 276 : else if (startchunk == endchunk)
666 : {
667 276 : ScanKeyInit(&toastkey[1],
668 : (AttrNumber) 2,
669 : BTEqualStrategyNumber, F_INT4EQ,
670 : Int32GetDatum(startchunk));
671 276 : nscankeys = 2;
672 : }
673 : else
674 : {
675 0 : ScanKeyInit(&toastkey[1],
676 : (AttrNumber) 2,
677 : BTGreaterEqualStrategyNumber, F_INT4GE,
678 : Int32GetDatum(startchunk));
679 0 : ScanKeyInit(&toastkey[2],
680 : (AttrNumber) 2,
681 : BTLessEqualStrategyNumber, F_INT4LE,
682 : Int32GetDatum(endchunk));
683 0 : nscankeys = 3;
684 : }
685 :
686 : /* Prepare for scan */
687 20140 : toastscan = systable_beginscan_ordered(toastrel, toastidxs[validIndex],
688 : get_toast_snapshot(), nscankeys, toastkey);
689 :
690 : /*
691 : * Read the chunks by index
692 : *
693 : * The index is on (valueid, chunkidx) so they will come in order
694 : */
695 20140 : expectedchunk = startchunk;
696 84920 : while ((ttup = systable_getnext_ordered(toastscan, ForwardScanDirection)) != NULL)
697 : {
698 : int32 curchunk;
699 : Pointer chunk;
700 : bool isnull;
701 : char *chunkdata;
702 : int32 chunksize;
703 : int32 expected_size;
704 : int32 chcpystrt;
705 : int32 chcpyend;
706 :
707 : /*
708 : * Have a chunk, extract the sequence number and the data
709 : */
710 64780 : curchunk = DatumGetInt32(fastgetattr(ttup, 2, toasttupDesc, &isnull));
711 : Assert(!isnull);
712 64780 : chunk = DatumGetPointer(fastgetattr(ttup, 3, toasttupDesc, &isnull));
713 : Assert(!isnull);
714 64780 : if (!VARATT_IS_EXTENDED(chunk))
715 : {
716 64780 : chunksize = VARSIZE(chunk) - VARHDRSZ;
717 64780 : chunkdata = VARDATA(chunk);
718 : }
719 0 : else if (VARATT_IS_SHORT(chunk))
720 : {
721 : /* could happen due to heap_form_tuple doing its thing */
722 0 : chunksize = VARSIZE_SHORT(chunk) - VARHDRSZ_SHORT;
723 0 : chunkdata = VARDATA_SHORT(chunk);
724 : }
725 : else
726 : {
727 : /* should never happen */
728 0 : elog(ERROR, "found toasted toast chunk for toast value %u in %s",
729 : valueid, RelationGetRelationName(toastrel));
730 : chunksize = 0; /* keep compiler quiet */
731 : chunkdata = NULL;
732 : }
733 :
734 : /*
735 : * Some checks on the data we've found
736 : */
737 64780 : if (curchunk != expectedchunk)
738 0 : ereport(ERROR,
739 : (errcode(ERRCODE_DATA_CORRUPTED),
740 : errmsg_internal("unexpected chunk number %d (expected %d) for toast value %u in %s",
741 : curchunk, expectedchunk, valueid,
742 : RelationGetRelationName(toastrel))));
743 64780 : if (curchunk > endchunk)
744 0 : ereport(ERROR,
745 : (errcode(ERRCODE_DATA_CORRUPTED),
746 : errmsg_internal("unexpected chunk number %d (out of range %d..%d) for toast value %u in %s",
747 : curchunk,
748 : startchunk, endchunk, valueid,
749 : RelationGetRelationName(toastrel))));
750 64780 : expected_size = curchunk < totalchunks - 1 ? TOAST_MAX_CHUNK_SIZE
751 19888 : : attrsize - ((totalchunks - 1) * TOAST_MAX_CHUNK_SIZE);
752 64780 : if (chunksize != expected_size)
753 0 : ereport(ERROR,
754 : (errcode(ERRCODE_DATA_CORRUPTED),
755 : errmsg_internal("unexpected chunk size %d (expected %d) in chunk %d of %d for toast value %u in %s",
756 : chunksize, expected_size,
757 : curchunk, totalchunks, valueid,
758 : RelationGetRelationName(toastrel))));
759 :
760 : /*
761 : * Copy the data into proper place in our result
762 : */
763 64780 : chcpystrt = 0;
764 64780 : chcpyend = chunksize - 1;
765 64780 : if (curchunk == startchunk)
766 20140 : chcpystrt = sliceoffset % TOAST_MAX_CHUNK_SIZE;
767 64780 : if (curchunk == endchunk)
768 20140 : chcpyend = (sliceoffset + slicelength - 1) % TOAST_MAX_CHUNK_SIZE;
769 :
770 64780 : memcpy(VARDATA(result) +
771 64780 : (curchunk * TOAST_MAX_CHUNK_SIZE - sliceoffset) + chcpystrt,
772 64780 : chunkdata + chcpystrt,
773 64780 : (chcpyend - chcpystrt) + 1);
774 :
775 64780 : expectedchunk++;
776 : }
777 :
778 : /*
779 : * Final checks that we successfully fetched the datum
780 : */
781 20140 : if (expectedchunk != (endchunk + 1))
782 0 : ereport(ERROR,
783 : (errcode(ERRCODE_DATA_CORRUPTED),
784 : errmsg_internal("missing chunk number %d for toast value %u in %s",
785 : expectedchunk, valueid,
786 : RelationGetRelationName(toastrel))));
787 :
788 : /* End scan and close indexes. */
789 20140 : systable_endscan_ordered(toastscan);
790 20140 : toast_close_indexes(toastidxs, num_indexes, AccessShareLock);
791 20140 : }
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