1 /*-------------------------------------------------------------------------
2 *
3 * tuptoaster.c
4 * Support routines for external and compressed storage of
5 * variable size attributes.
6 *
7 * Copyright (c) 2000-2016, PostgreSQL Global Development Group
8 *
9 *
10 * IDENTIFICATION
11 * src/backend/access/heap/tuptoaster.c
12 *
13 *
14 * INTERFACE ROUTINES
15 * toast_insert_or_update -
16 * Try to make a given tuple fit into one page by compressing
17 * or moving off attributes
18 *
19 * toast_delete -
20 * Reclaim toast storage when a tuple is deleted
21 *
22 * heap_tuple_untoast_attr -
23 * Fetch back a given value from the "secondary" relation
24 *
25 *-------------------------------------------------------------------------
26 */
27
28 #include "postgres.h"
29
30 #include <unistd.h>
31 #include <fcntl.h>
32
33 #include "access/genam.h"
34 #include "access/heapam.h"
35 #include "access/tuptoaster.h"
36 #include "access/xact.h"
37 #include "catalog/catalog.h"
38 #include "common/pg_lzcompress.h"
39 #include "miscadmin.h"
40 #include "utils/expandeddatum.h"
41 #include "utils/fmgroids.h"
42 #include "utils/rel.h"
43 #include "utils/snapmgr.h"
44 #include "utils/typcache.h"
45 #include "utils/tqual.h"
46
47
48 #undef TOAST_DEBUG
49
50 /*
51 * The information at the start of the compressed toast data.
52 */
53 typedef struct toast_compress_header
54 {
55 int32 vl_len_; /* varlena header (do not touch directly!) */
56 int32 rawsize;
57 } toast_compress_header;
58
59 /*
60 * Utilities for manipulation of header information for compressed
61 * toast entries.
62 */
63 #define TOAST_COMPRESS_HDRSZ ((int32) sizeof(toast_compress_header))
64 #define TOAST_COMPRESS_RAWSIZE(ptr) (((toast_compress_header *) (ptr))->rawsize)
65 #define TOAST_COMPRESS_RAWDATA(ptr) \
66 (((char *) (ptr)) + TOAST_COMPRESS_HDRSZ)
67 #define TOAST_COMPRESS_SET_RAWSIZE(ptr, len) \
68 (((toast_compress_header *) (ptr))->rawsize = (len))
69
70 static void toast_delete_datum(Relation rel, Datum value, bool is_speculative);
71 static Datum toast_save_datum(Relation rel, Datum value,
72 struct varlena * oldexternal, int options);
73 static bool toastrel_valueid_exists(Relation toastrel, Oid valueid);
74 static bool toastid_valueid_exists(Oid toastrelid, Oid valueid);
75 static struct varlena *toast_fetch_datum(struct varlena * attr);
76 static struct varlena *toast_fetch_datum_slice(struct varlena * attr,
77 int32 sliceoffset, int32 length);
78 static struct varlena *toast_decompress_datum(struct varlena * attr);
79 static int toast_open_indexes(Relation toastrel,
80 LOCKMODE lock,
81 Relation **toastidxs,
82 int *num_indexes);
83 static void toast_close_indexes(Relation *toastidxs, int num_indexes,
84 LOCKMODE lock);
85 static void init_toast_snapshot(Snapshot toast_snapshot);
86
87
88 /* ----------
89 * heap_tuple_fetch_attr -
90 *
91 * Public entry point to get back a toasted value from
92 * external source (possibly still in compressed format).
93 *
94 * This will return a datum that contains all the data internally, ie, not
95 * relying on external storage or memory, but it can still be compressed or
96 * have a short header. Note some callers assume that if the input is an
97 * EXTERNAL datum, the result will be a pfree'able chunk.
98 * ----------
99 */
100 struct varlena *
heap_tuple_fetch_attr(struct varlena * attr)101 heap_tuple_fetch_attr(struct varlena * attr)
102 {
103 struct varlena *result;
104
105 if (VARATT_IS_EXTERNAL_ONDISK(attr))
106 {
107 /*
108 * This is an external stored plain value
109 */
110 result = toast_fetch_datum(attr);
111 }
112 else if (VARATT_IS_EXTERNAL_INDIRECT(attr))
113 {
114 /*
115 * This is an indirect pointer --- dereference it
116 */
117 struct varatt_indirect redirect;
118
119 VARATT_EXTERNAL_GET_POINTER(redirect, attr);
120 attr = (struct varlena *) redirect.pointer;
121
122 /* nested indirect Datums aren't allowed */
123 Assert(!VARATT_IS_EXTERNAL_INDIRECT(attr));
124
125 /* recurse if value is still external in some other way */
126 if (VARATT_IS_EXTERNAL(attr))
127 return heap_tuple_fetch_attr(attr);
128
129 /*
130 * Copy into the caller's memory context, in case caller tries to
131 * pfree the result.
132 */
133 result = (struct varlena *) palloc(VARSIZE_ANY(attr));
134 memcpy(result, attr, VARSIZE_ANY(attr));
135 }
136 else if (VARATT_IS_EXTERNAL_EXPANDED(attr))
137 {
138 /*
139 * This is an expanded-object pointer --- get flat format
140 */
141 ExpandedObjectHeader *eoh;
142 Size resultsize;
143
144 eoh = DatumGetEOHP(PointerGetDatum(attr));
145 resultsize = EOH_get_flat_size(eoh);
146 result = (struct varlena *) palloc(resultsize);
147 EOH_flatten_into(eoh, (void *) result, resultsize);
148 }
149 else
150 {
151 /*
152 * This is a plain value inside of the main tuple - why am I called?
153 */
154 result = attr;
155 }
156
157 return result;
158 }
159
160
161 /* ----------
162 * heap_tuple_untoast_attr -
163 *
164 * Public entry point to get back a toasted value from compression
165 * or external storage. The result is always non-extended varlena form.
166 *
167 * Note some callers assume that if the input is an EXTERNAL or COMPRESSED
168 * datum, the result will be a pfree'able chunk.
169 * ----------
170 */
171 struct varlena *
heap_tuple_untoast_attr(struct varlena * attr)172 heap_tuple_untoast_attr(struct varlena * attr)
173 {
174 if (VARATT_IS_EXTERNAL_ONDISK(attr))
175 {
176 /*
177 * This is an externally stored datum --- fetch it back from there
178 */
179 attr = toast_fetch_datum(attr);
180 /* If it's compressed, decompress it */
181 if (VARATT_IS_COMPRESSED(attr))
182 {
183 struct varlena *tmp = attr;
184
185 attr = toast_decompress_datum(tmp);
186 pfree(tmp);
187 }
188 }
189 else if (VARATT_IS_EXTERNAL_INDIRECT(attr))
190 {
191 /*
192 * This is an indirect pointer --- dereference it
193 */
194 struct varatt_indirect redirect;
195
196 VARATT_EXTERNAL_GET_POINTER(redirect, attr);
197 attr = (struct varlena *) redirect.pointer;
198
199 /* nested indirect Datums aren't allowed */
200 Assert(!VARATT_IS_EXTERNAL_INDIRECT(attr));
201
202 /* recurse in case value is still extended in some other way */
203 attr = heap_tuple_untoast_attr(attr);
204
205 /* if it isn't, we'd better copy it */
206 if (attr == (struct varlena *) redirect.pointer)
207 {
208 struct varlena *result;
209
210 result = (struct varlena *) palloc(VARSIZE_ANY(attr));
211 memcpy(result, attr, VARSIZE_ANY(attr));
212 attr = result;
213 }
214 }
215 else if (VARATT_IS_EXTERNAL_EXPANDED(attr))
216 {
217 /*
218 * This is an expanded-object pointer --- get flat format
219 */
220 attr = heap_tuple_fetch_attr(attr);
221 /* flatteners are not allowed to produce compressed/short output */
222 Assert(!VARATT_IS_EXTENDED(attr));
223 }
224 else if (VARATT_IS_COMPRESSED(attr))
225 {
226 /*
227 * This is a compressed value inside of the main tuple
228 */
229 attr = toast_decompress_datum(attr);
230 }
231 else if (VARATT_IS_SHORT(attr))
232 {
233 /*
234 * This is a short-header varlena --- convert to 4-byte header format
235 */
236 Size data_size = VARSIZE_SHORT(attr) - VARHDRSZ_SHORT;
237 Size new_size = data_size + VARHDRSZ;
238 struct varlena *new_attr;
239
240 new_attr = (struct varlena *) palloc(new_size);
241 SET_VARSIZE(new_attr, new_size);
242 memcpy(VARDATA(new_attr), VARDATA_SHORT(attr), data_size);
243 attr = new_attr;
244 }
245
246 return attr;
247 }
248
249
250 /* ----------
251 * heap_tuple_untoast_attr_slice -
252 *
253 * Public entry point to get back part of a toasted value
254 * from compression or external storage.
255 * ----------
256 */
257 struct varlena *
heap_tuple_untoast_attr_slice(struct varlena * attr,int32 sliceoffset,int32 slicelength)258 heap_tuple_untoast_attr_slice(struct varlena * attr,
259 int32 sliceoffset, int32 slicelength)
260 {
261 struct varlena *preslice;
262 struct varlena *result;
263 char *attrdata;
264 int32 attrsize;
265
266 if (VARATT_IS_EXTERNAL_ONDISK(attr))
267 {
268 struct varatt_external toast_pointer;
269
270 VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
271
272 /* fast path for non-compressed external datums */
273 if (!VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer))
274 return toast_fetch_datum_slice(attr, sliceoffset, slicelength);
275
276 /* fetch it back (compressed marker will get set automatically) */
277 preslice = toast_fetch_datum(attr);
278 }
279 else if (VARATT_IS_EXTERNAL_INDIRECT(attr))
280 {
281 struct varatt_indirect redirect;
282
283 VARATT_EXTERNAL_GET_POINTER(redirect, attr);
284
285 /* nested indirect Datums aren't allowed */
286 Assert(!VARATT_IS_EXTERNAL_INDIRECT(redirect.pointer));
287
288 return heap_tuple_untoast_attr_slice(redirect.pointer,
289 sliceoffset, slicelength);
290 }
291 else if (VARATT_IS_EXTERNAL_EXPANDED(attr))
292 {
293 /* pass it off to heap_tuple_fetch_attr to flatten */
294 preslice = heap_tuple_fetch_attr(attr);
295 }
296 else
297 preslice = attr;
298
299 Assert(!VARATT_IS_EXTERNAL(preslice));
300
301 if (VARATT_IS_COMPRESSED(preslice))
302 {
303 struct varlena *tmp = preslice;
304
305 preslice = toast_decompress_datum(tmp);
306
307 if (tmp != attr)
308 pfree(tmp);
309 }
310
311 if (VARATT_IS_SHORT(preslice))
312 {
313 attrdata = VARDATA_SHORT(preslice);
314 attrsize = VARSIZE_SHORT(preslice) - VARHDRSZ_SHORT;
315 }
316 else
317 {
318 attrdata = VARDATA(preslice);
319 attrsize = VARSIZE(preslice) - VARHDRSZ;
320 }
321
322 /* slicing of datum for compressed cases and plain value */
323
324 if (sliceoffset >= attrsize)
325 {
326 sliceoffset = 0;
327 slicelength = 0;
328 }
329
330 if (((sliceoffset + slicelength) > attrsize) || slicelength < 0)
331 slicelength = attrsize - sliceoffset;
332
333 result = (struct varlena *) palloc(slicelength + VARHDRSZ);
334 SET_VARSIZE(result, slicelength + VARHDRSZ);
335
336 memcpy(VARDATA(result), attrdata + sliceoffset, slicelength);
337
338 if (preslice != attr)
339 pfree(preslice);
340
341 return result;
342 }
343
344
345 /* ----------
346 * toast_raw_datum_size -
347 *
348 * Return the raw (detoasted) size of a varlena datum
349 * (including the VARHDRSZ header)
350 * ----------
351 */
352 Size
toast_raw_datum_size(Datum value)353 toast_raw_datum_size(Datum value)
354 {
355 struct varlena *attr = (struct varlena *) DatumGetPointer(value);
356 Size result;
357
358 if (VARATT_IS_EXTERNAL_ONDISK(attr))
359 {
360 /* va_rawsize is the size of the original datum -- including header */
361 struct varatt_external toast_pointer;
362
363 VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
364 result = toast_pointer.va_rawsize;
365 }
366 else if (VARATT_IS_EXTERNAL_INDIRECT(attr))
367 {
368 struct varatt_indirect toast_pointer;
369
370 VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
371
372 /* nested indirect Datums aren't allowed */
373 Assert(!VARATT_IS_EXTERNAL_INDIRECT(toast_pointer.pointer));
374
375 return toast_raw_datum_size(PointerGetDatum(toast_pointer.pointer));
376 }
377 else if (VARATT_IS_EXTERNAL_EXPANDED(attr))
378 {
379 result = EOH_get_flat_size(DatumGetEOHP(value));
380 }
381 else if (VARATT_IS_COMPRESSED(attr))
382 {
383 /* here, va_rawsize is just the payload size */
384 result = VARRAWSIZE_4B_C(attr) + VARHDRSZ;
385 }
386 else if (VARATT_IS_SHORT(attr))
387 {
388 /*
389 * we have to normalize the header length to VARHDRSZ or else the
390 * callers of this function will be confused.
391 */
392 result = VARSIZE_SHORT(attr) - VARHDRSZ_SHORT + VARHDRSZ;
393 }
394 else
395 {
396 /* plain untoasted datum */
397 result = VARSIZE(attr);
398 }
399 return result;
400 }
401
402 /* ----------
403 * toast_datum_size
404 *
405 * Return the physical storage size (possibly compressed) of a varlena datum
406 * ----------
407 */
408 Size
toast_datum_size(Datum value)409 toast_datum_size(Datum value)
410 {
411 struct varlena *attr = (struct varlena *) DatumGetPointer(value);
412 Size result;
413
414 if (VARATT_IS_EXTERNAL_ONDISK(attr))
415 {
416 /*
417 * Attribute is stored externally - return the extsize whether
418 * compressed or not. We do not count the size of the toast pointer
419 * ... should we?
420 */
421 struct varatt_external toast_pointer;
422
423 VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
424 result = toast_pointer.va_extsize;
425 }
426 else if (VARATT_IS_EXTERNAL_INDIRECT(attr))
427 {
428 struct varatt_indirect toast_pointer;
429
430 VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
431
432 /* nested indirect Datums aren't allowed */
433 Assert(!VARATT_IS_EXTERNAL_INDIRECT(attr));
434
435 return toast_datum_size(PointerGetDatum(toast_pointer.pointer));
436 }
437 else if (VARATT_IS_EXTERNAL_EXPANDED(attr))
438 {
439 result = EOH_get_flat_size(DatumGetEOHP(value));
440 }
441 else if (VARATT_IS_SHORT(attr))
442 {
443 result = VARSIZE_SHORT(attr);
444 }
445 else
446 {
447 /*
448 * Attribute is stored inline either compressed or not, just calculate
449 * the size of the datum in either case.
450 */
451 result = VARSIZE(attr);
452 }
453 return result;
454 }
455
456
457 /* ----------
458 * toast_delete -
459 *
460 * Cascaded delete toast-entries on DELETE
461 * ----------
462 */
463 void
toast_delete(Relation rel,HeapTuple oldtup,bool is_speculative)464 toast_delete(Relation rel, HeapTuple oldtup, bool is_speculative)
465 {
466 TupleDesc tupleDesc;
467 Form_pg_attribute *att;
468 int numAttrs;
469 int i;
470 Datum toast_values[MaxHeapAttributeNumber];
471 bool toast_isnull[MaxHeapAttributeNumber];
472
473 /*
474 * We should only ever be called for tuples of plain relations or
475 * materialized views --- recursing on a toast rel is bad news.
476 */
477 Assert(rel->rd_rel->relkind == RELKIND_RELATION ||
478 rel->rd_rel->relkind == RELKIND_MATVIEW);
479
480 /*
481 * Get the tuple descriptor and break down the tuple into fields.
482 *
483 * NOTE: it's debatable whether to use heap_deform_tuple() here or just
484 * heap_getattr() only the varlena columns. The latter could win if there
485 * are few varlena columns and many non-varlena ones. However,
486 * heap_deform_tuple costs only O(N) while the heap_getattr way would cost
487 * O(N^2) if there are many varlena columns, so it seems better to err on
488 * the side of linear cost. (We won't even be here unless there's at
489 * least one varlena column, by the way.)
490 */
491 tupleDesc = rel->rd_att;
492 att = tupleDesc->attrs;
493 numAttrs = tupleDesc->natts;
494
495 Assert(numAttrs <= MaxHeapAttributeNumber);
496 heap_deform_tuple(oldtup, tupleDesc, toast_values, toast_isnull);
497
498 /*
499 * Check for external stored attributes and delete them from the secondary
500 * relation.
501 */
502 for (i = 0; i < numAttrs; i++)
503 {
504 if (att[i]->attlen == -1)
505 {
506 Datum value = toast_values[i];
507
508 if (toast_isnull[i])
509 continue;
510 else if (VARATT_IS_EXTERNAL_ONDISK(PointerGetDatum(value)))
511 toast_delete_datum(rel, value, is_speculative);
512 }
513 }
514 }
515
516
517 /* ----------
518 * toast_insert_or_update -
519 *
520 * Delete no-longer-used toast-entries and create new ones to
521 * make the new tuple fit on INSERT or UPDATE
522 *
523 * Inputs:
524 * newtup: the candidate new tuple to be inserted
525 * oldtup: the old row version for UPDATE, or NULL for INSERT
526 * options: options to be passed to heap_insert() for toast rows
527 * Result:
528 * either newtup if no toasting is needed, or a palloc'd modified tuple
529 * that is what should actually get stored
530 *
531 * NOTE: neither newtup nor oldtup will be modified. This is a change
532 * from the pre-8.1 API of this routine.
533 * ----------
534 */
535 HeapTuple
toast_insert_or_update(Relation rel,HeapTuple newtup,HeapTuple oldtup,int options)536 toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup,
537 int options)
538 {
539 HeapTuple result_tuple;
540 TupleDesc tupleDesc;
541 Form_pg_attribute *att;
542 int numAttrs;
543 int i;
544
545 bool need_change = false;
546 bool need_free = false;
547 bool need_delold = false;
548 bool has_nulls = false;
549
550 Size maxDataLen;
551 Size hoff;
552
553 char toast_action[MaxHeapAttributeNumber];
554 bool toast_isnull[MaxHeapAttributeNumber];
555 bool toast_oldisnull[MaxHeapAttributeNumber];
556 Datum toast_values[MaxHeapAttributeNumber];
557 Datum toast_oldvalues[MaxHeapAttributeNumber];
558 struct varlena *toast_oldexternal[MaxHeapAttributeNumber];
559 int32 toast_sizes[MaxHeapAttributeNumber];
560 bool toast_free[MaxHeapAttributeNumber];
561 bool toast_delold[MaxHeapAttributeNumber];
562
563 /*
564 * Ignore the INSERT_SPECULATIVE option. Speculative insertions/super
565 * deletions just normally insert/delete the toast values. It seems
566 * easiest to deal with that here, instead on, potentially, multiple
567 * callers.
568 */
569 options &= ~HEAP_INSERT_SPECULATIVE;
570
571 /*
572 * We should only ever be called for tuples of plain relations or
573 * materialized views --- recursing on a toast rel is bad news.
574 */
575 Assert(rel->rd_rel->relkind == RELKIND_RELATION ||
576 rel->rd_rel->relkind == RELKIND_MATVIEW);
577
578 /*
579 * Get the tuple descriptor and break down the tuple(s) into fields.
580 */
581 tupleDesc = rel->rd_att;
582 att = tupleDesc->attrs;
583 numAttrs = tupleDesc->natts;
584
585 Assert(numAttrs <= MaxHeapAttributeNumber);
586 heap_deform_tuple(newtup, tupleDesc, toast_values, toast_isnull);
587 if (oldtup != NULL)
588 heap_deform_tuple(oldtup, tupleDesc, toast_oldvalues, toast_oldisnull);
589
590 /* ----------
591 * Then collect information about the values given
592 *
593 * NOTE: toast_action[i] can have these values:
594 * ' ' default handling
595 * 'p' already processed --- don't touch it
596 * 'x' incompressible, but OK to move off
597 *
598 * NOTE: toast_sizes[i] is only made valid for varlena attributes with
599 * toast_action[i] different from 'p'.
600 * ----------
601 */
602 memset(toast_action, ' ', numAttrs * sizeof(char));
603 memset(toast_oldexternal, 0, numAttrs * sizeof(struct varlena *));
604 memset(toast_free, 0, numAttrs * sizeof(bool));
605 memset(toast_delold, 0, numAttrs * sizeof(bool));
606
607 for (i = 0; i < numAttrs; i++)
608 {
609 struct varlena *old_value;
610 struct varlena *new_value;
611
612 if (oldtup != NULL)
613 {
614 /*
615 * For UPDATE get the old and new values of this attribute
616 */
617 old_value = (struct varlena *) DatumGetPointer(toast_oldvalues[i]);
618 new_value = (struct varlena *) DatumGetPointer(toast_values[i]);
619
620 /*
621 * If the old value is stored on disk, check if it has changed so
622 * we have to delete it later.
623 */
624 if (att[i]->attlen == -1 && !toast_oldisnull[i] &&
625 VARATT_IS_EXTERNAL_ONDISK(old_value))
626 {
627 if (toast_isnull[i] || !VARATT_IS_EXTERNAL_ONDISK(new_value) ||
628 memcmp((char *) old_value, (char *) new_value,
629 VARSIZE_EXTERNAL(old_value)) != 0)
630 {
631 /*
632 * The old external stored value isn't needed any more
633 * after the update
634 */
635 toast_delold[i] = true;
636 need_delold = true;
637 }
638 else
639 {
640 /*
641 * This attribute isn't changed by this update so we reuse
642 * the original reference to the old value in the new
643 * tuple.
644 */
645 toast_action[i] = 'p';
646 continue;
647 }
648 }
649 }
650 else
651 {
652 /*
653 * For INSERT simply get the new value
654 */
655 new_value = (struct varlena *) DatumGetPointer(toast_values[i]);
656 }
657
658 /*
659 * Handle NULL attributes
660 */
661 if (toast_isnull[i])
662 {
663 toast_action[i] = 'p';
664 has_nulls = true;
665 continue;
666 }
667
668 /*
669 * Now look at varlena attributes
670 */
671 if (att[i]->attlen == -1)
672 {
673 /*
674 * If the table's attribute says PLAIN always, force it so.
675 */
676 if (att[i]->attstorage == 'p')
677 toast_action[i] = 'p';
678
679 /*
680 * We took care of UPDATE above, so any external value we find
681 * still in the tuple must be someone else's that we cannot reuse
682 * (this includes the case of an out-of-line in-memory datum).
683 * Fetch it back (without decompression, unless we are forcing
684 * PLAIN storage). If necessary, we'll push it out as a new
685 * external value below.
686 */
687 if (VARATT_IS_EXTERNAL(new_value))
688 {
689 toast_oldexternal[i] = new_value;
690 if (att[i]->attstorage == 'p')
691 new_value = heap_tuple_untoast_attr(new_value);
692 else
693 new_value = heap_tuple_fetch_attr(new_value);
694 toast_values[i] = PointerGetDatum(new_value);
695 toast_free[i] = true;
696 need_change = true;
697 need_free = true;
698 }
699
700 /*
701 * Remember the size of this attribute
702 */
703 toast_sizes[i] = VARSIZE_ANY(new_value);
704 }
705 else
706 {
707 /*
708 * Not a varlena attribute, plain storage always
709 */
710 toast_action[i] = 'p';
711 }
712 }
713
714 /* ----------
715 * Compress and/or save external until data fits into target length
716 *
717 * 1: Inline compress attributes with attstorage 'x', and store very
718 * large attributes with attstorage 'x' or 'e' external immediately
719 * 2: Store attributes with attstorage 'x' or 'e' external
720 * 3: Inline compress attributes with attstorage 'm'
721 * 4: Store attributes with attstorage 'm' external
722 * ----------
723 */
724
725 /* compute header overhead --- this should match heap_form_tuple() */
726 hoff = SizeofHeapTupleHeader;
727 if (has_nulls)
728 hoff += BITMAPLEN(numAttrs);
729 if (newtup->t_data->t_infomask & HEAP_HASOID)
730 hoff += sizeof(Oid);
731 hoff = MAXALIGN(hoff);
732 /* now convert to a limit on the tuple data size */
733 maxDataLen = TOAST_TUPLE_TARGET - hoff;
734
735 /*
736 * Look for attributes with attstorage 'x' to compress. Also find large
737 * attributes with attstorage 'x' or 'e', and store them external.
738 */
739 while (heap_compute_data_size(tupleDesc,
740 toast_values, toast_isnull) > maxDataLen)
741 {
742 int biggest_attno = -1;
743 int32 biggest_size = MAXALIGN(TOAST_POINTER_SIZE);
744 Datum old_value;
745 Datum new_value;
746
747 /*
748 * Search for the biggest yet unprocessed internal attribute
749 */
750 for (i = 0; i < numAttrs; i++)
751 {
752 if (toast_action[i] != ' ')
753 continue;
754 if (VARATT_IS_EXTERNAL(DatumGetPointer(toast_values[i])))
755 continue; /* can't happen, toast_action would be 'p' */
756 if (VARATT_IS_COMPRESSED(DatumGetPointer(toast_values[i])))
757 continue;
758 if (att[i]->attstorage != 'x' && att[i]->attstorage != 'e')
759 continue;
760 if (toast_sizes[i] > biggest_size)
761 {
762 biggest_attno = i;
763 biggest_size = toast_sizes[i];
764 }
765 }
766
767 if (biggest_attno < 0)
768 break;
769
770 /*
771 * Attempt to compress it inline, if it has attstorage 'x'
772 */
773 i = biggest_attno;
774 if (att[i]->attstorage == 'x')
775 {
776 old_value = toast_values[i];
777 new_value = toast_compress_datum(old_value);
778
779 if (DatumGetPointer(new_value) != NULL)
780 {
781 /* successful compression */
782 if (toast_free[i])
783 pfree(DatumGetPointer(old_value));
784 toast_values[i] = new_value;
785 toast_free[i] = true;
786 toast_sizes[i] = VARSIZE(DatumGetPointer(toast_values[i]));
787 need_change = true;
788 need_free = true;
789 }
790 else
791 {
792 /* incompressible, ignore on subsequent compression passes */
793 toast_action[i] = 'x';
794 }
795 }
796 else
797 {
798 /* has attstorage 'e', ignore on subsequent compression passes */
799 toast_action[i] = 'x';
800 }
801
802 /*
803 * If this value is by itself more than maxDataLen (after compression
804 * if any), push it out to the toast table immediately, if possible.
805 * This avoids uselessly compressing other fields in the common case
806 * where we have one long field and several short ones.
807 *
808 * XXX maybe the threshold should be less than maxDataLen?
809 */
810 if (toast_sizes[i] > maxDataLen &&
811 rel->rd_rel->reltoastrelid != InvalidOid)
812 {
813 old_value = toast_values[i];
814 toast_action[i] = 'p';
815 toast_values[i] = toast_save_datum(rel, toast_values[i],
816 toast_oldexternal[i], options);
817 if (toast_free[i])
818 pfree(DatumGetPointer(old_value));
819 toast_free[i] = true;
820 need_change = true;
821 need_free = true;
822 }
823 }
824
825 /*
826 * Second we look for attributes of attstorage 'x' or 'e' that are still
827 * inline. But skip this if there's no toast table to push them to.
828 */
829 while (heap_compute_data_size(tupleDesc,
830 toast_values, toast_isnull) > maxDataLen &&
831 rel->rd_rel->reltoastrelid != InvalidOid)
832 {
833 int biggest_attno = -1;
834 int32 biggest_size = MAXALIGN(TOAST_POINTER_SIZE);
835 Datum old_value;
836
837 /*------
838 * Search for the biggest yet inlined attribute with
839 * attstorage equals 'x' or 'e'
840 *------
841 */
842 for (i = 0; i < numAttrs; i++)
843 {
844 if (toast_action[i] == 'p')
845 continue;
846 if (VARATT_IS_EXTERNAL(DatumGetPointer(toast_values[i])))
847 continue; /* can't happen, toast_action would be 'p' */
848 if (att[i]->attstorage != 'x' && att[i]->attstorage != 'e')
849 continue;
850 if (toast_sizes[i] > biggest_size)
851 {
852 biggest_attno = i;
853 biggest_size = toast_sizes[i];
854 }
855 }
856
857 if (biggest_attno < 0)
858 break;
859
860 /*
861 * Store this external
862 */
863 i = biggest_attno;
864 old_value = toast_values[i];
865 toast_action[i] = 'p';
866 toast_values[i] = toast_save_datum(rel, toast_values[i],
867 toast_oldexternal[i], options);
868 if (toast_free[i])
869 pfree(DatumGetPointer(old_value));
870 toast_free[i] = true;
871
872 need_change = true;
873 need_free = true;
874 }
875
876 /*
877 * Round 3 - this time we take attributes with storage 'm' into
878 * compression
879 */
880 while (heap_compute_data_size(tupleDesc,
881 toast_values, toast_isnull) > maxDataLen)
882 {
883 int biggest_attno = -1;
884 int32 biggest_size = MAXALIGN(TOAST_POINTER_SIZE);
885 Datum old_value;
886 Datum new_value;
887
888 /*
889 * Search for the biggest yet uncompressed internal attribute
890 */
891 for (i = 0; i < numAttrs; i++)
892 {
893 if (toast_action[i] != ' ')
894 continue;
895 if (VARATT_IS_EXTERNAL(DatumGetPointer(toast_values[i])))
896 continue; /* can't happen, toast_action would be 'p' */
897 if (VARATT_IS_COMPRESSED(DatumGetPointer(toast_values[i])))
898 continue;
899 if (att[i]->attstorage != 'm')
900 continue;
901 if (toast_sizes[i] > biggest_size)
902 {
903 biggest_attno = i;
904 biggest_size = toast_sizes[i];
905 }
906 }
907
908 if (biggest_attno < 0)
909 break;
910
911 /*
912 * Attempt to compress it inline
913 */
914 i = biggest_attno;
915 old_value = toast_values[i];
916 new_value = toast_compress_datum(old_value);
917
918 if (DatumGetPointer(new_value) != NULL)
919 {
920 /* successful compression */
921 if (toast_free[i])
922 pfree(DatumGetPointer(old_value));
923 toast_values[i] = new_value;
924 toast_free[i] = true;
925 toast_sizes[i] = VARSIZE(DatumGetPointer(toast_values[i]));
926 need_change = true;
927 need_free = true;
928 }
929 else
930 {
931 /* incompressible, ignore on subsequent compression passes */
932 toast_action[i] = 'x';
933 }
934 }
935
936 /*
937 * Finally we store attributes of type 'm' externally. At this point we
938 * increase the target tuple size, so that 'm' attributes aren't stored
939 * externally unless really necessary.
940 */
941 maxDataLen = TOAST_TUPLE_TARGET_MAIN - hoff;
942
943 while (heap_compute_data_size(tupleDesc,
944 toast_values, toast_isnull) > maxDataLen &&
945 rel->rd_rel->reltoastrelid != InvalidOid)
946 {
947 int biggest_attno = -1;
948 int32 biggest_size = MAXALIGN(TOAST_POINTER_SIZE);
949 Datum old_value;
950
951 /*--------
952 * Search for the biggest yet inlined attribute with
953 * attstorage = 'm'
954 *--------
955 */
956 for (i = 0; i < numAttrs; i++)
957 {
958 if (toast_action[i] == 'p')
959 continue;
960 if (VARATT_IS_EXTERNAL(DatumGetPointer(toast_values[i])))
961 continue; /* can't happen, toast_action would be 'p' */
962 if (att[i]->attstorage != 'm')
963 continue;
964 if (toast_sizes[i] > biggest_size)
965 {
966 biggest_attno = i;
967 biggest_size = toast_sizes[i];
968 }
969 }
970
971 if (biggest_attno < 0)
972 break;
973
974 /*
975 * Store this external
976 */
977 i = biggest_attno;
978 old_value = toast_values[i];
979 toast_action[i] = 'p';
980 toast_values[i] = toast_save_datum(rel, toast_values[i],
981 toast_oldexternal[i], options);
982 if (toast_free[i])
983 pfree(DatumGetPointer(old_value));
984 toast_free[i] = true;
985
986 need_change = true;
987 need_free = true;
988 }
989
990 /*
991 * In the case we toasted any values, we need to build a new heap tuple
992 * with the changed values.
993 */
994 if (need_change)
995 {
996 HeapTupleHeader olddata = newtup->t_data;
997 HeapTupleHeader new_data;
998 int32 new_header_len;
999 int32 new_data_len;
1000 int32 new_tuple_len;
1001
1002 /*
1003 * Calculate the new size of the tuple.
1004 *
1005 * Note: we used to assume here that the old tuple's t_hoff must equal
1006 * the new_header_len value, but that was incorrect. The old tuple
1007 * might have a smaller-than-current natts, if there's been an ALTER
1008 * TABLE ADD COLUMN since it was stored; and that would lead to a
1009 * different conclusion about the size of the null bitmap, or even
1010 * whether there needs to be one at all.
1011 */
1012 new_header_len = SizeofHeapTupleHeader;
1013 if (has_nulls)
1014 new_header_len += BITMAPLEN(numAttrs);
1015 if (olddata->t_infomask & HEAP_HASOID)
1016 new_header_len += sizeof(Oid);
1017 new_header_len = MAXALIGN(new_header_len);
1018 new_data_len = heap_compute_data_size(tupleDesc,
1019 toast_values, toast_isnull);
1020 new_tuple_len = new_header_len + new_data_len;
1021
1022 /*
1023 * Allocate and zero the space needed, and fill HeapTupleData fields.
1024 */
1025 result_tuple = (HeapTuple) palloc0(HEAPTUPLESIZE + new_tuple_len);
1026 result_tuple->t_len = new_tuple_len;
1027 result_tuple->t_self = newtup->t_self;
1028 result_tuple->t_tableOid = newtup->t_tableOid;
1029 new_data = (HeapTupleHeader) ((char *) result_tuple + HEAPTUPLESIZE);
1030 result_tuple->t_data = new_data;
1031
1032 /*
1033 * Copy the existing tuple header, but adjust natts and t_hoff.
1034 */
1035 memcpy(new_data, olddata, SizeofHeapTupleHeader);
1036 HeapTupleHeaderSetNatts(new_data, numAttrs);
1037 new_data->t_hoff = new_header_len;
1038 if (olddata->t_infomask & HEAP_HASOID)
1039 HeapTupleHeaderSetOid(new_data, HeapTupleHeaderGetOid(olddata));
1040
1041 /* Copy over the data, and fill the null bitmap if needed */
1042 heap_fill_tuple(tupleDesc,
1043 toast_values,
1044 toast_isnull,
1045 (char *) new_data + new_header_len,
1046 new_data_len,
1047 &(new_data->t_infomask),
1048 has_nulls ? new_data->t_bits : NULL);
1049 }
1050 else
1051 result_tuple = newtup;
1052
1053 /*
1054 * Free allocated temp values
1055 */
1056 if (need_free)
1057 for (i = 0; i < numAttrs; i++)
1058 if (toast_free[i])
1059 pfree(DatumGetPointer(toast_values[i]));
1060
1061 /*
1062 * Delete external values from the old tuple
1063 */
1064 if (need_delold)
1065 for (i = 0; i < numAttrs; i++)
1066 if (toast_delold[i])
1067 toast_delete_datum(rel, toast_oldvalues[i], false);
1068
1069 return result_tuple;
1070 }
1071
1072
1073 /* ----------
1074 * toast_flatten_tuple -
1075 *
1076 * "Flatten" a tuple to contain no out-of-line toasted fields.
1077 * (This does not eliminate compressed or short-header datums.)
1078 *
1079 * Note: we expect the caller already checked HeapTupleHasExternal(tup),
1080 * so there is no need for a short-circuit path.
1081 * ----------
1082 */
1083 HeapTuple
toast_flatten_tuple(HeapTuple tup,TupleDesc tupleDesc)1084 toast_flatten_tuple(HeapTuple tup, TupleDesc tupleDesc)
1085 {
1086 HeapTuple new_tuple;
1087 Form_pg_attribute *att = tupleDesc->attrs;
1088 int numAttrs = tupleDesc->natts;
1089 int i;
1090 Datum toast_values[MaxTupleAttributeNumber];
1091 bool toast_isnull[MaxTupleAttributeNumber];
1092 bool toast_free[MaxTupleAttributeNumber];
1093
1094 /*
1095 * Break down the tuple into fields.
1096 */
1097 Assert(numAttrs <= MaxTupleAttributeNumber);
1098 heap_deform_tuple(tup, tupleDesc, toast_values, toast_isnull);
1099
1100 memset(toast_free, 0, numAttrs * sizeof(bool));
1101
1102 for (i = 0; i < numAttrs; i++)
1103 {
1104 /*
1105 * Look at non-null varlena attributes
1106 */
1107 if (!toast_isnull[i] && att[i]->attlen == -1)
1108 {
1109 struct varlena *new_value;
1110
1111 new_value = (struct varlena *) DatumGetPointer(toast_values[i]);
1112 if (VARATT_IS_EXTERNAL(new_value))
1113 {
1114 new_value = heap_tuple_fetch_attr(new_value);
1115 toast_values[i] = PointerGetDatum(new_value);
1116 toast_free[i] = true;
1117 }
1118 }
1119 }
1120
1121 /*
1122 * Form the reconfigured tuple.
1123 */
1124 new_tuple = heap_form_tuple(tupleDesc, toast_values, toast_isnull);
1125
1126 /*
1127 * Be sure to copy the tuple's OID and identity fields. We also make a
1128 * point of copying visibility info, just in case anybody looks at those
1129 * fields in a syscache entry.
1130 */
1131 if (tupleDesc->tdhasoid)
1132 HeapTupleSetOid(new_tuple, HeapTupleGetOid(tup));
1133
1134 new_tuple->t_self = tup->t_self;
1135 new_tuple->t_tableOid = tup->t_tableOid;
1136
1137 new_tuple->t_data->t_choice = tup->t_data->t_choice;
1138 new_tuple->t_data->t_ctid = tup->t_data->t_ctid;
1139 new_tuple->t_data->t_infomask &= ~HEAP_XACT_MASK;
1140 new_tuple->t_data->t_infomask |=
1141 tup->t_data->t_infomask & HEAP_XACT_MASK;
1142 new_tuple->t_data->t_infomask2 &= ~HEAP2_XACT_MASK;
1143 new_tuple->t_data->t_infomask2 |=
1144 tup->t_data->t_infomask2 & HEAP2_XACT_MASK;
1145
1146 /*
1147 * Free allocated temp values
1148 */
1149 for (i = 0; i < numAttrs; i++)
1150 if (toast_free[i])
1151 pfree(DatumGetPointer(toast_values[i]));
1152
1153 return new_tuple;
1154 }
1155
1156
1157 /* ----------
1158 * toast_flatten_tuple_to_datum -
1159 *
1160 * "Flatten" a tuple containing out-of-line toasted fields into a Datum.
1161 * The result is always palloc'd in the current memory context.
1162 *
1163 * We have a general rule that Datums of container types (rows, arrays,
1164 * ranges, etc) must not contain any external TOAST pointers. Without
1165 * this rule, we'd have to look inside each Datum when preparing a tuple
1166 * for storage, which would be expensive and would fail to extend cleanly
1167 * to new sorts of container types.
1168 *
1169 * However, we don't want to say that tuples represented as HeapTuples
1170 * can't contain toasted fields, so instead this routine should be called
1171 * when such a HeapTuple is being converted into a Datum.
1172 *
1173 * While we're at it, we decompress any compressed fields too. This is not
1174 * necessary for correctness, but reflects an expectation that compression
1175 * will be more effective if applied to the whole tuple not individual
1176 * fields. We are not so concerned about that that we want to deconstruct
1177 * and reconstruct tuples just to get rid of compressed fields, however.
1178 * So callers typically won't call this unless they see that the tuple has
1179 * at least one external field.
1180 *
1181 * On the other hand, in-line short-header varlena fields are left alone.
1182 * If we "untoasted" them here, they'd just get changed back to short-header
1183 * format anyway within heap_fill_tuple.
1184 * ----------
1185 */
1186 Datum
toast_flatten_tuple_to_datum(HeapTupleHeader tup,uint32 tup_len,TupleDesc tupleDesc)1187 toast_flatten_tuple_to_datum(HeapTupleHeader tup,
1188 uint32 tup_len,
1189 TupleDesc tupleDesc)
1190 {
1191 HeapTupleHeader new_data;
1192 int32 new_header_len;
1193 int32 new_data_len;
1194 int32 new_tuple_len;
1195 HeapTupleData tmptup;
1196 Form_pg_attribute *att = tupleDesc->attrs;
1197 int numAttrs = tupleDesc->natts;
1198 int i;
1199 bool has_nulls = false;
1200 Datum toast_values[MaxTupleAttributeNumber];
1201 bool toast_isnull[MaxTupleAttributeNumber];
1202 bool toast_free[MaxTupleAttributeNumber];
1203
1204 /* Build a temporary HeapTuple control structure */
1205 tmptup.t_len = tup_len;
1206 ItemPointerSetInvalid(&(tmptup.t_self));
1207 tmptup.t_tableOid = InvalidOid;
1208 tmptup.t_data = tup;
1209
1210 /*
1211 * Break down the tuple into fields.
1212 */
1213 Assert(numAttrs <= MaxTupleAttributeNumber);
1214 heap_deform_tuple(&tmptup, tupleDesc, toast_values, toast_isnull);
1215
1216 memset(toast_free, 0, numAttrs * sizeof(bool));
1217
1218 for (i = 0; i < numAttrs; i++)
1219 {
1220 /*
1221 * Look at non-null varlena attributes
1222 */
1223 if (toast_isnull[i])
1224 has_nulls = true;
1225 else if (att[i]->attlen == -1)
1226 {
1227 struct varlena *new_value;
1228
1229 new_value = (struct varlena *) DatumGetPointer(toast_values[i]);
1230 if (VARATT_IS_EXTERNAL(new_value) ||
1231 VARATT_IS_COMPRESSED(new_value))
1232 {
1233 new_value = heap_tuple_untoast_attr(new_value);
1234 toast_values[i] = PointerGetDatum(new_value);
1235 toast_free[i] = true;
1236 }
1237 }
1238 }
1239
1240 /*
1241 * Calculate the new size of the tuple.
1242 *
1243 * This should match the reconstruction code in toast_insert_or_update.
1244 */
1245 new_header_len = SizeofHeapTupleHeader;
1246 if (has_nulls)
1247 new_header_len += BITMAPLEN(numAttrs);
1248 if (tup->t_infomask & HEAP_HASOID)
1249 new_header_len += sizeof(Oid);
1250 new_header_len = MAXALIGN(new_header_len);
1251 new_data_len = heap_compute_data_size(tupleDesc,
1252 toast_values, toast_isnull);
1253 new_tuple_len = new_header_len + new_data_len;
1254
1255 new_data = (HeapTupleHeader) palloc0(new_tuple_len);
1256
1257 /*
1258 * Copy the existing tuple header, but adjust natts and t_hoff.
1259 */
1260 memcpy(new_data, tup, SizeofHeapTupleHeader);
1261 HeapTupleHeaderSetNatts(new_data, numAttrs);
1262 new_data->t_hoff = new_header_len;
1263 if (tup->t_infomask & HEAP_HASOID)
1264 HeapTupleHeaderSetOid(new_data, HeapTupleHeaderGetOid(tup));
1265
1266 /* Set the composite-Datum header fields correctly */
1267 HeapTupleHeaderSetDatumLength(new_data, new_tuple_len);
1268 HeapTupleHeaderSetTypeId(new_data, tupleDesc->tdtypeid);
1269 HeapTupleHeaderSetTypMod(new_data, tupleDesc->tdtypmod);
1270
1271 /* Copy over the data, and fill the null bitmap if needed */
1272 heap_fill_tuple(tupleDesc,
1273 toast_values,
1274 toast_isnull,
1275 (char *) new_data + new_header_len,
1276 new_data_len,
1277 &(new_data->t_infomask),
1278 has_nulls ? new_data->t_bits : NULL);
1279
1280 /*
1281 * Free allocated temp values
1282 */
1283 for (i = 0; i < numAttrs; i++)
1284 if (toast_free[i])
1285 pfree(DatumGetPointer(toast_values[i]));
1286
1287 return PointerGetDatum(new_data);
1288 }
1289
1290
1291 /* ----------
1292 * toast_compress_datum -
1293 *
1294 * Create a compressed version of a varlena datum
1295 *
1296 * If we fail (ie, compressed result is actually bigger than original)
1297 * then return NULL. We must not use compressed data if it'd expand
1298 * the tuple!
1299 *
1300 * We use VAR{SIZE,DATA}_ANY so we can handle short varlenas here without
1301 * copying them. But we can't handle external or compressed datums.
1302 * ----------
1303 */
1304 Datum
toast_compress_datum(Datum value)1305 toast_compress_datum(Datum value)
1306 {
1307 struct varlena *tmp;
1308 int32 valsize = VARSIZE_ANY_EXHDR(DatumGetPointer(value));
1309 int32 len;
1310
1311 Assert(!VARATT_IS_EXTERNAL(DatumGetPointer(value)));
1312 Assert(!VARATT_IS_COMPRESSED(DatumGetPointer(value)));
1313
1314 /*
1315 * No point in wasting a palloc cycle if value size is out of the allowed
1316 * range for compression
1317 */
1318 if (valsize < PGLZ_strategy_default->min_input_size ||
1319 valsize > PGLZ_strategy_default->max_input_size)
1320 return PointerGetDatum(NULL);
1321
1322 tmp = (struct varlena *) palloc(PGLZ_MAX_OUTPUT(valsize) +
1323 TOAST_COMPRESS_HDRSZ);
1324
1325 /*
1326 * We recheck the actual size even if pglz_compress() reports success,
1327 * because it might be satisfied with having saved as little as one byte
1328 * in the compressed data --- which could turn into a net loss once you
1329 * consider header and alignment padding. Worst case, the compressed
1330 * format might require three padding bytes (plus header, which is
1331 * included in VARSIZE(tmp)), whereas the uncompressed format would take
1332 * only one header byte and no padding if the value is short enough. So
1333 * we insist on a savings of more than 2 bytes to ensure we have a gain.
1334 */
1335 len = pglz_compress(VARDATA_ANY(DatumGetPointer(value)),
1336 valsize,
1337 TOAST_COMPRESS_RAWDATA(tmp),
1338 PGLZ_strategy_default);
1339 if (len >= 0 &&
1340 len + TOAST_COMPRESS_HDRSZ < valsize - 2)
1341 {
1342 TOAST_COMPRESS_SET_RAWSIZE(tmp, valsize);
1343 SET_VARSIZE_COMPRESSED(tmp, len + TOAST_COMPRESS_HDRSZ);
1344 /* successful compression */
1345 return PointerGetDatum(tmp);
1346 }
1347 else
1348 {
1349 /* incompressible data */
1350 pfree(tmp);
1351 return PointerGetDatum(NULL);
1352 }
1353 }
1354
1355
1356 /* ----------
1357 * toast_get_valid_index
1358 *
1359 * Get OID of valid index associated to given toast relation. A toast
1360 * relation can have only one valid index at the same time.
1361 */
1362 Oid
toast_get_valid_index(Oid toastoid,LOCKMODE lock)1363 toast_get_valid_index(Oid toastoid, LOCKMODE lock)
1364 {
1365 int num_indexes;
1366 int validIndex;
1367 Oid validIndexOid;
1368 Relation *toastidxs;
1369 Relation toastrel;
1370
1371 /* Open the toast relation */
1372 toastrel = heap_open(toastoid, lock);
1373
1374 /* Look for the valid index of the toast relation */
1375 validIndex = toast_open_indexes(toastrel,
1376 lock,
1377 &toastidxs,
1378 &num_indexes);
1379 validIndexOid = RelationGetRelid(toastidxs[validIndex]);
1380
1381 /* Close the toast relation and all its indexes */
1382 toast_close_indexes(toastidxs, num_indexes, NoLock);
1383 heap_close(toastrel, NoLock);
1384
1385 return validIndexOid;
1386 }
1387
1388
1389 /* ----------
1390 * toast_save_datum -
1391 *
1392 * Save one single datum into the secondary relation and return
1393 * a Datum reference for it.
1394 *
1395 * rel: the main relation we're working with (not the toast rel!)
1396 * value: datum to be pushed to toast storage
1397 * oldexternal: if not NULL, toast pointer previously representing the datum
1398 * options: options to be passed to heap_insert() for toast rows
1399 * ----------
1400 */
1401 static Datum
toast_save_datum(Relation rel,Datum value,struct varlena * oldexternal,int options)1402 toast_save_datum(Relation rel, Datum value,
1403 struct varlena * oldexternal, int options)
1404 {
1405 Relation toastrel;
1406 Relation *toastidxs;
1407 HeapTuple toasttup;
1408 TupleDesc toasttupDesc;
1409 Datum t_values[3];
1410 bool t_isnull[3];
1411 CommandId mycid = GetCurrentCommandId(true);
1412 struct varlena *result;
1413 struct varatt_external toast_pointer;
1414 union
1415 {
1416 struct varlena hdr;
1417 /* this is to make the union big enough for a chunk: */
1418 char data[TOAST_MAX_CHUNK_SIZE + VARHDRSZ];
1419 /* ensure union is aligned well enough: */
1420 int32 align_it;
1421 } chunk_data;
1422 int32 chunk_size;
1423 int32 chunk_seq = 0;
1424 char *data_p;
1425 int32 data_todo;
1426 Pointer dval = DatumGetPointer(value);
1427 int num_indexes;
1428 int validIndex;
1429
1430 Assert(!VARATT_IS_EXTERNAL(value));
1431
1432 /*
1433 * Open the toast relation and its indexes. We can use the index to check
1434 * uniqueness of the OID we assign to the toasted item, even though it has
1435 * additional columns besides OID.
1436 */
1437 toastrel = heap_open(rel->rd_rel->reltoastrelid, RowExclusiveLock);
1438 toasttupDesc = toastrel->rd_att;
1439
1440 /* Open all the toast indexes and look for the valid one */
1441 validIndex = toast_open_indexes(toastrel,
1442 RowExclusiveLock,
1443 &toastidxs,
1444 &num_indexes);
1445
1446 /*
1447 * Get the data pointer and length, and compute va_rawsize and va_extsize.
1448 *
1449 * va_rawsize is the size of the equivalent fully uncompressed datum, so
1450 * we have to adjust for short headers.
1451 *
1452 * va_extsize is the actual size of the data payload in the toast records.
1453 */
1454 if (VARATT_IS_SHORT(dval))
1455 {
1456 data_p = VARDATA_SHORT(dval);
1457 data_todo = VARSIZE_SHORT(dval) - VARHDRSZ_SHORT;
1458 toast_pointer.va_rawsize = data_todo + VARHDRSZ; /* as if not short */
1459 toast_pointer.va_extsize = data_todo;
1460 }
1461 else if (VARATT_IS_COMPRESSED(dval))
1462 {
1463 data_p = VARDATA(dval);
1464 data_todo = VARSIZE(dval) - VARHDRSZ;
1465 /* rawsize in a compressed datum is just the size of the payload */
1466 toast_pointer.va_rawsize = VARRAWSIZE_4B_C(dval) + VARHDRSZ;
1467 toast_pointer.va_extsize = data_todo;
1468 /* Assert that the numbers look like it's compressed */
1469 Assert(VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer));
1470 }
1471 else
1472 {
1473 data_p = VARDATA(dval);
1474 data_todo = VARSIZE(dval) - VARHDRSZ;
1475 toast_pointer.va_rawsize = VARSIZE(dval);
1476 toast_pointer.va_extsize = data_todo;
1477 }
1478
1479 /*
1480 * Insert the correct table OID into the result TOAST pointer.
1481 *
1482 * Normally this is the actual OID of the target toast table, but during
1483 * table-rewriting operations such as CLUSTER, we have to insert the OID
1484 * of the table's real permanent toast table instead. rd_toastoid is set
1485 * if we have to substitute such an OID.
1486 */
1487 if (OidIsValid(rel->rd_toastoid))
1488 toast_pointer.va_toastrelid = rel->rd_toastoid;
1489 else
1490 toast_pointer.va_toastrelid = RelationGetRelid(toastrel);
1491
1492 /*
1493 * Choose an OID to use as the value ID for this toast value.
1494 *
1495 * Normally we just choose an unused OID within the toast table. But
1496 * during table-rewriting operations where we are preserving an existing
1497 * toast table OID, we want to preserve toast value OIDs too. So, if
1498 * rd_toastoid is set and we had a prior external value from that same
1499 * toast table, re-use its value ID. If we didn't have a prior external
1500 * value (which is a corner case, but possible if the table's attstorage
1501 * options have been changed), we have to pick a value ID that doesn't
1502 * conflict with either new or existing toast value OIDs.
1503 */
1504 if (!OidIsValid(rel->rd_toastoid))
1505 {
1506 /* normal case: just choose an unused OID */
1507 toast_pointer.va_valueid =
1508 GetNewOidWithIndex(toastrel,
1509 RelationGetRelid(toastidxs[validIndex]),
1510 (AttrNumber) 1);
1511 }
1512 else
1513 {
1514 /* rewrite case: check to see if value was in old toast table */
1515 toast_pointer.va_valueid = InvalidOid;
1516 if (oldexternal != NULL)
1517 {
1518 struct varatt_external old_toast_pointer;
1519
1520 Assert(VARATT_IS_EXTERNAL_ONDISK(oldexternal));
1521 /* Must copy to access aligned fields */
1522 VARATT_EXTERNAL_GET_POINTER(old_toast_pointer, oldexternal);
1523 if (old_toast_pointer.va_toastrelid == rel->rd_toastoid)
1524 {
1525 /* This value came from the old toast table; reuse its OID */
1526 toast_pointer.va_valueid = old_toast_pointer.va_valueid;
1527
1528 /*
1529 * There is a corner case here: the table rewrite might have
1530 * to copy both live and recently-dead versions of a row, and
1531 * those versions could easily reference the same toast value.
1532 * When we copy the second or later version of such a row,
1533 * reusing the OID will mean we select an OID that's already
1534 * in the new toast table. Check for that, and if so, just
1535 * fall through without writing the data again.
1536 *
1537 * While annoying and ugly-looking, this is a good thing
1538 * because it ensures that we wind up with only one copy of
1539 * the toast value when there is only one copy in the old
1540 * toast table. Before we detected this case, we'd have made
1541 * multiple copies, wasting space; and what's worse, the
1542 * copies belonging to already-deleted heap tuples would not
1543 * be reclaimed by VACUUM.
1544 */
1545 if (toastrel_valueid_exists(toastrel,
1546 toast_pointer.va_valueid))
1547 {
1548 /* Match, so short-circuit the data storage loop below */
1549 data_todo = 0;
1550 }
1551 }
1552 }
1553 if (toast_pointer.va_valueid == InvalidOid)
1554 {
1555 /*
1556 * new value; must choose an OID that doesn't conflict in either
1557 * old or new toast table
1558 */
1559 do
1560 {
1561 toast_pointer.va_valueid =
1562 GetNewOidWithIndex(toastrel,
1563 RelationGetRelid(toastidxs[validIndex]),
1564 (AttrNumber) 1);
1565 } while (toastid_valueid_exists(rel->rd_toastoid,
1566 toast_pointer.va_valueid));
1567 }
1568 }
1569
1570 /*
1571 * Initialize constant parts of the tuple data
1572 */
1573 t_values[0] = ObjectIdGetDatum(toast_pointer.va_valueid);
1574 t_values[2] = PointerGetDatum(&chunk_data);
1575 t_isnull[0] = false;
1576 t_isnull[1] = false;
1577 t_isnull[2] = false;
1578
1579 /*
1580 * Split up the item into chunks
1581 */
1582 while (data_todo > 0)
1583 {
1584 int i;
1585
1586 CHECK_FOR_INTERRUPTS();
1587
1588 /*
1589 * Calculate the size of this chunk
1590 */
1591 chunk_size = Min(TOAST_MAX_CHUNK_SIZE, data_todo);
1592
1593 /*
1594 * Build a tuple and store it
1595 */
1596 t_values[1] = Int32GetDatum(chunk_seq++);
1597 SET_VARSIZE(&chunk_data, chunk_size + VARHDRSZ);
1598 memcpy(VARDATA(&chunk_data), data_p, chunk_size);
1599 toasttup = heap_form_tuple(toasttupDesc, t_values, t_isnull);
1600
1601 heap_insert(toastrel, toasttup, mycid, options, NULL);
1602
1603 /*
1604 * Create the index entry. We cheat a little here by not using
1605 * FormIndexDatum: this relies on the knowledge that the index columns
1606 * are the same as the initial columns of the table for all the
1607 * indexes.
1608 *
1609 * Note also that there had better not be any user-created index on
1610 * the TOAST table, since we don't bother to update anything else.
1611 */
1612 for (i = 0; i < num_indexes; i++)
1613 {
1614 /* Only index relations marked as ready can be updated */
1615 if (IndexIsReady(toastidxs[i]->rd_index))
1616 index_insert(toastidxs[i], t_values, t_isnull,
1617 &(toasttup->t_self),
1618 toastrel,
1619 toastidxs[i]->rd_index->indisunique ?
1620 UNIQUE_CHECK_YES : UNIQUE_CHECK_NO);
1621 }
1622
1623 /*
1624 * Free memory
1625 */
1626 heap_freetuple(toasttup);
1627
1628 /*
1629 * Move on to next chunk
1630 */
1631 data_todo -= chunk_size;
1632 data_p += chunk_size;
1633 }
1634
1635 /*
1636 * Done - close toast relation and its indexes
1637 */
1638 toast_close_indexes(toastidxs, num_indexes, RowExclusiveLock);
1639 heap_close(toastrel, RowExclusiveLock);
1640
1641 /*
1642 * Create the TOAST pointer value that we'll return
1643 */
1644 result = (struct varlena *) palloc(TOAST_POINTER_SIZE);
1645 SET_VARTAG_EXTERNAL(result, VARTAG_ONDISK);
1646 memcpy(VARDATA_EXTERNAL(result), &toast_pointer, sizeof(toast_pointer));
1647
1648 return PointerGetDatum(result);
1649 }
1650
1651
1652 /* ----------
1653 * toast_delete_datum -
1654 *
1655 * Delete a single external stored value.
1656 * ----------
1657 */
1658 static void
toast_delete_datum(Relation rel,Datum value,bool is_speculative)1659 toast_delete_datum(Relation rel, Datum value, bool is_speculative)
1660 {
1661 struct varlena *attr = (struct varlena *) DatumGetPointer(value);
1662 struct varatt_external toast_pointer;
1663 Relation toastrel;
1664 Relation *toastidxs;
1665 ScanKeyData toastkey;
1666 SysScanDesc toastscan;
1667 HeapTuple toasttup;
1668 int num_indexes;
1669 int validIndex;
1670 SnapshotData SnapshotToast;
1671
1672 if (!VARATT_IS_EXTERNAL_ONDISK(attr))
1673 return;
1674
1675 /* Must copy to access aligned fields */
1676 VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
1677
1678 /*
1679 * Open the toast relation and its indexes
1680 */
1681 toastrel = heap_open(toast_pointer.va_toastrelid, RowExclusiveLock);
1682
1683 /* Fetch valid relation used for process */
1684 validIndex = toast_open_indexes(toastrel,
1685 RowExclusiveLock,
1686 &toastidxs,
1687 &num_indexes);
1688
1689 /*
1690 * Setup a scan key to find chunks with matching va_valueid
1691 */
1692 ScanKeyInit(&toastkey,
1693 (AttrNumber) 1,
1694 BTEqualStrategyNumber, F_OIDEQ,
1695 ObjectIdGetDatum(toast_pointer.va_valueid));
1696
1697 /*
1698 * Find all the chunks. (We don't actually care whether we see them in
1699 * sequence or not, but since we've already locked the index we might as
1700 * well use systable_beginscan_ordered.)
1701 */
1702 init_toast_snapshot(&SnapshotToast);
1703 toastscan = systable_beginscan_ordered(toastrel, toastidxs[validIndex],
1704 &SnapshotToast, 1, &toastkey);
1705 while ((toasttup = systable_getnext_ordered(toastscan, ForwardScanDirection)) != NULL)
1706 {
1707 /*
1708 * Have a chunk, delete it
1709 */
1710 if (is_speculative)
1711 heap_abort_speculative(toastrel, toasttup);
1712 else
1713 simple_heap_delete(toastrel, &toasttup->t_self);
1714 }
1715
1716 /*
1717 * End scan and close relations
1718 */
1719 systable_endscan_ordered(toastscan);
1720 toast_close_indexes(toastidxs, num_indexes, RowExclusiveLock);
1721 heap_close(toastrel, RowExclusiveLock);
1722 }
1723
1724
1725 /* ----------
1726 * toastrel_valueid_exists -
1727 *
1728 * Test whether a toast value with the given ID exists in the toast relation.
1729 * For safety, we consider a value to exist if there are either live or dead
1730 * toast rows with that ID; see notes for GetNewOid().
1731 * ----------
1732 */
1733 static bool
toastrel_valueid_exists(Relation toastrel,Oid valueid)1734 toastrel_valueid_exists(Relation toastrel, Oid valueid)
1735 {
1736 bool result = false;
1737 ScanKeyData toastkey;
1738 SysScanDesc toastscan;
1739 int num_indexes;
1740 int validIndex;
1741 Relation *toastidxs;
1742
1743 /* Fetch a valid index relation */
1744 validIndex = toast_open_indexes(toastrel,
1745 RowExclusiveLock,
1746 &toastidxs,
1747 &num_indexes);
1748
1749 /*
1750 * Setup a scan key to find chunks with matching va_valueid
1751 */
1752 ScanKeyInit(&toastkey,
1753 (AttrNumber) 1,
1754 BTEqualStrategyNumber, F_OIDEQ,
1755 ObjectIdGetDatum(valueid));
1756
1757 /*
1758 * Is there any such chunk?
1759 */
1760 toastscan = systable_beginscan(toastrel,
1761 RelationGetRelid(toastidxs[validIndex]),
1762 true, SnapshotAny, 1, &toastkey);
1763
1764 if (systable_getnext(toastscan) != NULL)
1765 result = true;
1766
1767 systable_endscan(toastscan);
1768
1769 /* Clean up */
1770 toast_close_indexes(toastidxs, num_indexes, RowExclusiveLock);
1771
1772 return result;
1773 }
1774
1775 /* ----------
1776 * toastid_valueid_exists -
1777 *
1778 * As above, but work from toast rel's OID not an open relation
1779 * ----------
1780 */
1781 static bool
toastid_valueid_exists(Oid toastrelid,Oid valueid)1782 toastid_valueid_exists(Oid toastrelid, Oid valueid)
1783 {
1784 bool result;
1785 Relation toastrel;
1786
1787 toastrel = heap_open(toastrelid, AccessShareLock);
1788
1789 result = toastrel_valueid_exists(toastrel, valueid);
1790
1791 heap_close(toastrel, AccessShareLock);
1792
1793 return result;
1794 }
1795
1796
1797 /* ----------
1798 * toast_fetch_datum -
1799 *
1800 * Reconstruct an in memory Datum from the chunks saved
1801 * in the toast relation
1802 * ----------
1803 */
1804 static struct varlena *
toast_fetch_datum(struct varlena * attr)1805 toast_fetch_datum(struct varlena * attr)
1806 {
1807 Relation toastrel;
1808 Relation *toastidxs;
1809 ScanKeyData toastkey;
1810 SysScanDesc toastscan;
1811 HeapTuple ttup;
1812 TupleDesc toasttupDesc;
1813 struct varlena *result;
1814 struct varatt_external toast_pointer;
1815 int32 ressize;
1816 int32 residx,
1817 nextidx;
1818 int32 numchunks;
1819 Pointer chunk;
1820 bool isnull;
1821 char *chunkdata;
1822 int32 chunksize;
1823 int num_indexes;
1824 int validIndex;
1825 SnapshotData SnapshotToast;
1826
1827 if (!VARATT_IS_EXTERNAL_ONDISK(attr))
1828 elog(ERROR, "toast_fetch_datum shouldn't be called for non-ondisk datums");
1829
1830 /* Must copy to access aligned fields */
1831 VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
1832
1833 ressize = toast_pointer.va_extsize;
1834 numchunks = ((ressize - 1) / TOAST_MAX_CHUNK_SIZE) + 1;
1835
1836 result = (struct varlena *) palloc(ressize + VARHDRSZ);
1837
1838 if (VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer))
1839 SET_VARSIZE_COMPRESSED(result, ressize + VARHDRSZ);
1840 else
1841 SET_VARSIZE(result, ressize + VARHDRSZ);
1842
1843 /*
1844 * Open the toast relation and its indexes
1845 */
1846 toastrel = heap_open(toast_pointer.va_toastrelid, AccessShareLock);
1847 toasttupDesc = toastrel->rd_att;
1848
1849 /* Look for the valid index of the toast relation */
1850 validIndex = toast_open_indexes(toastrel,
1851 AccessShareLock,
1852 &toastidxs,
1853 &num_indexes);
1854
1855 /*
1856 * Setup a scan key to fetch from the index by va_valueid
1857 */
1858 ScanKeyInit(&toastkey,
1859 (AttrNumber) 1,
1860 BTEqualStrategyNumber, F_OIDEQ,
1861 ObjectIdGetDatum(toast_pointer.va_valueid));
1862
1863 /*
1864 * Read the chunks by index
1865 *
1866 * Note that because the index is actually on (valueid, chunkidx) we will
1867 * see the chunks in chunkidx order, even though we didn't explicitly ask
1868 * for it.
1869 */
1870 nextidx = 0;
1871
1872 init_toast_snapshot(&SnapshotToast);
1873 toastscan = systable_beginscan_ordered(toastrel, toastidxs[validIndex],
1874 &SnapshotToast, 1, &toastkey);
1875 while ((ttup = systable_getnext_ordered(toastscan, ForwardScanDirection)) != NULL)
1876 {
1877 /*
1878 * Have a chunk, extract the sequence number and the data
1879 */
1880 residx = DatumGetInt32(fastgetattr(ttup, 2, toasttupDesc, &isnull));
1881 Assert(!isnull);
1882 chunk = DatumGetPointer(fastgetattr(ttup, 3, toasttupDesc, &isnull));
1883 Assert(!isnull);
1884 if (!VARATT_IS_EXTENDED(chunk))
1885 {
1886 chunksize = VARSIZE(chunk) - VARHDRSZ;
1887 chunkdata = VARDATA(chunk);
1888 }
1889 else if (VARATT_IS_SHORT(chunk))
1890 {
1891 /* could happen due to heap_form_tuple doing its thing */
1892 chunksize = VARSIZE_SHORT(chunk) - VARHDRSZ_SHORT;
1893 chunkdata = VARDATA_SHORT(chunk);
1894 }
1895 else
1896 {
1897 /* should never happen */
1898 elog(ERROR, "found toasted toast chunk for toast value %u in %s",
1899 toast_pointer.va_valueid,
1900 RelationGetRelationName(toastrel));
1901 chunksize = 0; /* keep compiler quiet */
1902 chunkdata = NULL;
1903 }
1904
1905 /*
1906 * Some checks on the data we've found
1907 */
1908 if (residx != nextidx)
1909 elog(ERROR, "unexpected chunk number %d (expected %d) for toast value %u in %s",
1910 residx, nextidx,
1911 toast_pointer.va_valueid,
1912 RelationGetRelationName(toastrel));
1913 if (residx < numchunks - 1)
1914 {
1915 if (chunksize != TOAST_MAX_CHUNK_SIZE)
1916 elog(ERROR, "unexpected chunk size %d (expected %d) in chunk %d of %d for toast value %u in %s",
1917 chunksize, (int) TOAST_MAX_CHUNK_SIZE,
1918 residx, numchunks,
1919 toast_pointer.va_valueid,
1920 RelationGetRelationName(toastrel));
1921 }
1922 else if (residx == numchunks - 1)
1923 {
1924 if ((residx * TOAST_MAX_CHUNK_SIZE + chunksize) != ressize)
1925 elog(ERROR, "unexpected chunk size %d (expected %d) in final chunk %d for toast value %u in %s",
1926 chunksize,
1927 (int) (ressize - residx * TOAST_MAX_CHUNK_SIZE),
1928 residx,
1929 toast_pointer.va_valueid,
1930 RelationGetRelationName(toastrel));
1931 }
1932 else
1933 elog(ERROR, "unexpected chunk number %d (out of range %d..%d) for toast value %u in %s",
1934 residx,
1935 0, numchunks - 1,
1936 toast_pointer.va_valueid,
1937 RelationGetRelationName(toastrel));
1938
1939 /*
1940 * Copy the data into proper place in our result
1941 */
1942 memcpy(VARDATA(result) + residx * TOAST_MAX_CHUNK_SIZE,
1943 chunkdata,
1944 chunksize);
1945
1946 nextidx++;
1947 }
1948
1949 /*
1950 * Final checks that we successfully fetched the datum
1951 */
1952 if (nextidx != numchunks)
1953 elog(ERROR, "missing chunk number %d for toast value %u in %s",
1954 nextidx,
1955 toast_pointer.va_valueid,
1956 RelationGetRelationName(toastrel));
1957
1958 /*
1959 * End scan and close relations
1960 */
1961 systable_endscan_ordered(toastscan);
1962 toast_close_indexes(toastidxs, num_indexes, AccessShareLock);
1963 heap_close(toastrel, AccessShareLock);
1964
1965 return result;
1966 }
1967
1968 /* ----------
1969 * toast_fetch_datum_slice -
1970 *
1971 * Reconstruct a segment of a Datum from the chunks saved
1972 * in the toast relation
1973 * ----------
1974 */
1975 static struct varlena *
toast_fetch_datum_slice(struct varlena * attr,int32 sliceoffset,int32 length)1976 toast_fetch_datum_slice(struct varlena * attr, int32 sliceoffset, int32 length)
1977 {
1978 Relation toastrel;
1979 Relation *toastidxs;
1980 ScanKeyData toastkey[3];
1981 int nscankeys;
1982 SysScanDesc toastscan;
1983 HeapTuple ttup;
1984 TupleDesc toasttupDesc;
1985 struct varlena *result;
1986 struct varatt_external toast_pointer;
1987 int32 attrsize;
1988 int32 residx;
1989 int32 nextidx;
1990 int numchunks;
1991 int startchunk;
1992 int endchunk;
1993 int32 startoffset;
1994 int32 endoffset;
1995 int totalchunks;
1996 Pointer chunk;
1997 bool isnull;
1998 char *chunkdata;
1999 int32 chunksize;
2000 int32 chcpystrt;
2001 int32 chcpyend;
2002 int num_indexes;
2003 int validIndex;
2004 SnapshotData SnapshotToast;
2005
2006 if (!VARATT_IS_EXTERNAL_ONDISK(attr))
2007 elog(ERROR, "toast_fetch_datum_slice shouldn't be called for non-ondisk datums");
2008
2009 /* Must copy to access aligned fields */
2010 VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
2011
2012 /*
2013 * It's nonsense to fetch slices of a compressed datum -- this isn't lo_*
2014 * we can't return a compressed datum which is meaningful to toast later
2015 */
2016 Assert(!VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer));
2017
2018 attrsize = toast_pointer.va_extsize;
2019 totalchunks = ((attrsize - 1) / TOAST_MAX_CHUNK_SIZE) + 1;
2020
2021 if (sliceoffset >= attrsize)
2022 {
2023 sliceoffset = 0;
2024 length = 0;
2025 }
2026
2027 if (((sliceoffset + length) > attrsize) || length < 0)
2028 length = attrsize - sliceoffset;
2029
2030 result = (struct varlena *) palloc(length + VARHDRSZ);
2031
2032 if (VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer))
2033 SET_VARSIZE_COMPRESSED(result, length + VARHDRSZ);
2034 else
2035 SET_VARSIZE(result, length + VARHDRSZ);
2036
2037 if (length == 0)
2038 return result; /* Can save a lot of work at this point! */
2039
2040 startchunk = sliceoffset / TOAST_MAX_CHUNK_SIZE;
2041 endchunk = (sliceoffset + length - 1) / TOAST_MAX_CHUNK_SIZE;
2042 numchunks = (endchunk - startchunk) + 1;
2043
2044 startoffset = sliceoffset % TOAST_MAX_CHUNK_SIZE;
2045 endoffset = (sliceoffset + length - 1) % TOAST_MAX_CHUNK_SIZE;
2046
2047 /*
2048 * Open the toast relation and its indexes
2049 */
2050 toastrel = heap_open(toast_pointer.va_toastrelid, AccessShareLock);
2051 toasttupDesc = toastrel->rd_att;
2052
2053 /* Look for the valid index of toast relation */
2054 validIndex = toast_open_indexes(toastrel,
2055 AccessShareLock,
2056 &toastidxs,
2057 &num_indexes);
2058
2059 /*
2060 * Setup a scan key to fetch from the index. This is either two keys or
2061 * three depending on the number of chunks.
2062 */
2063 ScanKeyInit(&toastkey[0],
2064 (AttrNumber) 1,
2065 BTEqualStrategyNumber, F_OIDEQ,
2066 ObjectIdGetDatum(toast_pointer.va_valueid));
2067
2068 /*
2069 * Use equality condition for one chunk, a range condition otherwise:
2070 */
2071 if (numchunks == 1)
2072 {
2073 ScanKeyInit(&toastkey[1],
2074 (AttrNumber) 2,
2075 BTEqualStrategyNumber, F_INT4EQ,
2076 Int32GetDatum(startchunk));
2077 nscankeys = 2;
2078 }
2079 else
2080 {
2081 ScanKeyInit(&toastkey[1],
2082 (AttrNumber) 2,
2083 BTGreaterEqualStrategyNumber, F_INT4GE,
2084 Int32GetDatum(startchunk));
2085 ScanKeyInit(&toastkey[2],
2086 (AttrNumber) 2,
2087 BTLessEqualStrategyNumber, F_INT4LE,
2088 Int32GetDatum(endchunk));
2089 nscankeys = 3;
2090 }
2091
2092 /*
2093 * Read the chunks by index
2094 *
2095 * The index is on (valueid, chunkidx) so they will come in order
2096 */
2097 init_toast_snapshot(&SnapshotToast);
2098 nextidx = startchunk;
2099 toastscan = systable_beginscan_ordered(toastrel, toastidxs[validIndex],
2100 &SnapshotToast, nscankeys, toastkey);
2101 while ((ttup = systable_getnext_ordered(toastscan, ForwardScanDirection)) != NULL)
2102 {
2103 /*
2104 * Have a chunk, extract the sequence number and the data
2105 */
2106 residx = DatumGetInt32(fastgetattr(ttup, 2, toasttupDesc, &isnull));
2107 Assert(!isnull);
2108 chunk = DatumGetPointer(fastgetattr(ttup, 3, toasttupDesc, &isnull));
2109 Assert(!isnull);
2110 if (!VARATT_IS_EXTENDED(chunk))
2111 {
2112 chunksize = VARSIZE(chunk) - VARHDRSZ;
2113 chunkdata = VARDATA(chunk);
2114 }
2115 else if (VARATT_IS_SHORT(chunk))
2116 {
2117 /* could happen due to heap_form_tuple doing its thing */
2118 chunksize = VARSIZE_SHORT(chunk) - VARHDRSZ_SHORT;
2119 chunkdata = VARDATA_SHORT(chunk);
2120 }
2121 else
2122 {
2123 /* should never happen */
2124 elog(ERROR, "found toasted toast chunk for toast value %u in %s",
2125 toast_pointer.va_valueid,
2126 RelationGetRelationName(toastrel));
2127 chunksize = 0; /* keep compiler quiet */
2128 chunkdata = NULL;
2129 }
2130
2131 /*
2132 * Some checks on the data we've found
2133 */
2134 if ((residx != nextidx) || (residx > endchunk) || (residx < startchunk))
2135 elog(ERROR, "unexpected chunk number %d (expected %d) for toast value %u in %s",
2136 residx, nextidx,
2137 toast_pointer.va_valueid,
2138 RelationGetRelationName(toastrel));
2139 if (residx < totalchunks - 1)
2140 {
2141 if (chunksize != TOAST_MAX_CHUNK_SIZE)
2142 elog(ERROR, "unexpected chunk size %d (expected %d) in chunk %d of %d for toast value %u in %s when fetching slice",
2143 chunksize, (int) TOAST_MAX_CHUNK_SIZE,
2144 residx, totalchunks,
2145 toast_pointer.va_valueid,
2146 RelationGetRelationName(toastrel));
2147 }
2148 else if (residx == totalchunks - 1)
2149 {
2150 if ((residx * TOAST_MAX_CHUNK_SIZE + chunksize) != attrsize)
2151 elog(ERROR, "unexpected chunk size %d (expected %d) in final chunk %d for toast value %u in %s when fetching slice",
2152 chunksize,
2153 (int) (attrsize - residx * TOAST_MAX_CHUNK_SIZE),
2154 residx,
2155 toast_pointer.va_valueid,
2156 RelationGetRelationName(toastrel));
2157 }
2158 else
2159 elog(ERROR, "unexpected chunk number %d (out of range %d..%d) for toast value %u in %s",
2160 residx,
2161 0, totalchunks - 1,
2162 toast_pointer.va_valueid,
2163 RelationGetRelationName(toastrel));
2164
2165 /*
2166 * Copy the data into proper place in our result
2167 */
2168 chcpystrt = 0;
2169 chcpyend = chunksize - 1;
2170 if (residx == startchunk)
2171 chcpystrt = startoffset;
2172 if (residx == endchunk)
2173 chcpyend = endoffset;
2174
2175 memcpy(VARDATA(result) +
2176 (residx * TOAST_MAX_CHUNK_SIZE - sliceoffset) + chcpystrt,
2177 chunkdata + chcpystrt,
2178 (chcpyend - chcpystrt) + 1);
2179
2180 nextidx++;
2181 }
2182
2183 /*
2184 * Final checks that we successfully fetched the datum
2185 */
2186 if (nextidx != (endchunk + 1))
2187 elog(ERROR, "missing chunk number %d for toast value %u in %s",
2188 nextidx,
2189 toast_pointer.va_valueid,
2190 RelationGetRelationName(toastrel));
2191
2192 /*
2193 * End scan and close relations
2194 */
2195 systable_endscan_ordered(toastscan);
2196 toast_close_indexes(toastidxs, num_indexes, AccessShareLock);
2197 heap_close(toastrel, AccessShareLock);
2198
2199 return result;
2200 }
2201
2202 /* ----------
2203 * toast_decompress_datum -
2204 *
2205 * Decompress a compressed version of a varlena datum
2206 */
2207 static struct varlena *
toast_decompress_datum(struct varlena * attr)2208 toast_decompress_datum(struct varlena * attr)
2209 {
2210 struct varlena *result;
2211
2212 Assert(VARATT_IS_COMPRESSED(attr));
2213
2214 result = (struct varlena *)
2215 palloc(TOAST_COMPRESS_RAWSIZE(attr) + VARHDRSZ);
2216 SET_VARSIZE(result, TOAST_COMPRESS_RAWSIZE(attr) + VARHDRSZ);
2217
2218 if (pglz_decompress(TOAST_COMPRESS_RAWDATA(attr),
2219 VARSIZE(attr) - TOAST_COMPRESS_HDRSZ,
2220 VARDATA(result),
2221 TOAST_COMPRESS_RAWSIZE(attr)) < 0)
2222 elog(ERROR, "compressed data is corrupted");
2223
2224 return result;
2225 }
2226
2227
2228 /* ----------
2229 * toast_open_indexes
2230 *
2231 * Get an array of the indexes associated to the given toast relation
2232 * and return as well the position of the valid index used by the toast
2233 * relation in this array. It is the responsibility of the caller of this
2234 * function to close the indexes as well as free them.
2235 */
2236 static int
toast_open_indexes(Relation toastrel,LOCKMODE lock,Relation ** toastidxs,int * num_indexes)2237 toast_open_indexes(Relation toastrel,
2238 LOCKMODE lock,
2239 Relation **toastidxs,
2240 int *num_indexes)
2241 {
2242 int i = 0;
2243 int res = 0;
2244 bool found = false;
2245 List *indexlist;
2246 ListCell *lc;
2247
2248 /* Get index list of the toast relation */
2249 indexlist = RelationGetIndexList(toastrel);
2250 Assert(indexlist != NIL);
2251
2252 *num_indexes = list_length(indexlist);
2253
2254 /* Open all the index relations */
2255 *toastidxs = (Relation *) palloc(*num_indexes * sizeof(Relation));
2256 foreach(lc, indexlist)
2257 (*toastidxs)[i++] = index_open(lfirst_oid(lc), lock);
2258
2259 /* Fetch the first valid index in list */
2260 for (i = 0; i < *num_indexes; i++)
2261 {
2262 Relation toastidx = (*toastidxs)[i];
2263
2264 if (toastidx->rd_index->indisvalid)
2265 {
2266 res = i;
2267 found = true;
2268 break;
2269 }
2270 }
2271
2272 /*
2273 * Free index list, not necessary anymore as relations are opened and a
2274 * valid index has been found.
2275 */
2276 list_free(indexlist);
2277
2278 /*
2279 * The toast relation should have one valid index, so something is going
2280 * wrong if there is nothing.
2281 */
2282 if (!found)
2283 elog(ERROR, "no valid index found for toast relation with Oid %u",
2284 RelationGetRelid(toastrel));
2285
2286 return res;
2287 }
2288
2289 /* ----------
2290 * toast_close_indexes
2291 *
2292 * Close an array of indexes for a toast relation and free it. This should
2293 * be called for a set of indexes opened previously with toast_open_indexes.
2294 */
2295 static void
toast_close_indexes(Relation * toastidxs,int num_indexes,LOCKMODE lock)2296 toast_close_indexes(Relation *toastidxs, int num_indexes, LOCKMODE lock)
2297 {
2298 int i;
2299
2300 /* Close relations and clean up things */
2301 for (i = 0; i < num_indexes; i++)
2302 index_close(toastidxs[i], lock);
2303 pfree(toastidxs);
2304 }
2305
2306 /* ----------
2307 * init_toast_snapshot
2308 *
2309 * Initialize an appropriate TOAST snapshot. We must use an MVCC snapshot
2310 * to initialize the TOAST snapshot; since we don't know which one to use,
2311 * just use the oldest one. This is safe: at worst, we will get a "snapshot
2312 * too old" error that might have been avoided otherwise.
2313 */
2314 static void
init_toast_snapshot(Snapshot toast_snapshot)2315 init_toast_snapshot(Snapshot toast_snapshot)
2316 {
2317 Snapshot snapshot = GetOldestSnapshot();
2318
2319 if (snapshot == NULL)
2320 elog(ERROR, "no known snapshots");
2321
2322 InitToastSnapshot(*toast_snapshot, snapshot->lsn, snapshot->whenTaken);
2323 }
2324