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Commitce242ae

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tableam: New callback relation_fetch_toast_slice.
Instead of always calling heap_fetch_toast_slice during detoasting,invoke a table AM callback which, when the toast table is a heaptable, will be heap_fetch_toast_slice.This makes it possible for a table AM other than heap to be usedas a TOAST table. It also completes the series of commits intendedto improve the interaction of tableam with TOAST that began withcommit8b94dab; detoast.c isnow, hopefully, fully AM-independent.Patch by me, reviewed by Andres Freund and Peter Eisentraut.Discussion:http://postgr.es/m/CA+TgmoZv-=2iWM4jcw5ZhJeL18HF96+W1yJeYrnGMYdkFFnEpQ@mail.gmail.com
1 parent83322e3 commitce242ae

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5 files changed

+245
-193
lines changed

5 files changed

+245
-193
lines changed

‎src/backend/access/common/detoast.c‎

Lines changed: 6 additions & 193 deletions
Original file line numberDiff line numberDiff line change
@@ -14,22 +14,17 @@
1414
#include"postgres.h"
1515

1616
#include"access/detoast.h"
17-
#include"access/genam.h"
18-
#include"access/heaptoast.h"
1917
#include"access/table.h"
18+
#include"access/tableam.h"
2019
#include"access/toast_internals.h"
2120
#include"common/pg_lzcompress.h"
2221
#include"utils/expandeddatum.h"
23-
#include"utils/fmgroids.h"
2422
#include"utils/rel.h"
2523

2624
staticstructvarlena*toast_fetch_datum(structvarlena*attr);
2725
staticstructvarlena*toast_fetch_datum_slice(structvarlena*attr,
2826
int32sliceoffset,
2927
int32slicelength);
30-
staticvoidheap_fetch_toast_slice(Relationtoastrel,Oidvalueid,
31-
int32attrsize,int32sliceoffset,
32-
int32slicelength,structvarlena*result);
3328
staticstructvarlena*toast_decompress_datum(structvarlena*attr);
3429
staticstructvarlena*toast_decompress_datum_slice(structvarlena*attr,int32slicelength);
3530

@@ -356,8 +351,8 @@ toast_fetch_datum(struct varlena *attr)
356351
toastrel=table_open(toast_pointer.va_toastrelid,AccessShareLock);
357352

358353
/* Fetch all chunks */
359-
heap_fetch_toast_slice(toastrel,toast_pointer.va_valueid,attrsize,0,
360-
attrsize,result);
354+
table_relation_fetch_toast_slice(toastrel,toast_pointer.va_valueid,
355+
attrsize,0,attrsize,result);
361356

362357
/* Close toast table */
363358
table_close(toastrel,AccessShareLock);
@@ -431,198 +426,16 @@ toast_fetch_datum_slice(struct varlena *attr, int32 sliceoffset,
431426
toastrel=table_open(toast_pointer.va_toastrelid,AccessShareLock);
432427

433428
/* Fetch all chunks */
434-
heap_fetch_toast_slice(toastrel,toast_pointer.va_valueid,attrsize,
435-
sliceoffset,slicelength,result);
429+
table_relation_fetch_toast_slice(toastrel,toast_pointer.va_valueid,
430+
attrsize,sliceoffset,slicelength,
431+
result);
436432

437433
/* Close toast table */
438434
table_close(toastrel,AccessShareLock);
439435

440436
returnresult;
441437
}
442438

443-
/*
444-
* Fetch a TOAST slice from a heap table.
445-
*
446-
* toastrel is the relation from which chunks are to be fetched.
447-
* valueid identifies the TOAST value from which chunks are being fetched.
448-
* attrsize is the total size of the TOAST value.
449-
* sliceoffset is the byte offset within the TOAST value from which to fetch.
450-
* slicelength is the number of bytes to be fetched from the TOAST value.
451-
* result is the varlena into which the results should be written.
452-
*/
453-
staticvoid
454-
heap_fetch_toast_slice(Relationtoastrel,Oidvalueid,int32attrsize,
455-
int32sliceoffset,int32slicelength,
456-
structvarlena*result)
457-
{
458-
Relation*toastidxs;
459-
ScanKeyDatatoastkey[3];
460-
TupleDesctoasttupDesc=toastrel->rd_att;
461-
intnscankeys;
462-
SysScanDesctoastscan;
463-
HeapTuplettup;
464-
int32expectedchunk;
465-
int32totalchunks= ((attrsize-1) /TOAST_MAX_CHUNK_SIZE)+1;
466-
intstartchunk;
467-
intendchunk;
468-
intnum_indexes;
469-
intvalidIndex;
470-
SnapshotDataSnapshotToast;
471-
472-
/* Look for the valid index of toast relation */
473-
validIndex=toast_open_indexes(toastrel,
474-
AccessShareLock,
475-
&toastidxs,
476-
&num_indexes);
477-
478-
startchunk=sliceoffset /TOAST_MAX_CHUNK_SIZE;
479-
endchunk= (sliceoffset+slicelength-1) /TOAST_MAX_CHUNK_SIZE;
480-
Assert(endchunk <=totalchunks);
481-
482-
/*
483-
* Setup a scan key to fetch from the index. This is either two keys or
484-
* three depending on the number of chunks.
485-
*/
486-
ScanKeyInit(&toastkey[0],
487-
(AttrNumber)1,
488-
BTEqualStrategyNumber,F_OIDEQ,
489-
ObjectIdGetDatum(valueid));
490-
491-
/*
492-
* No additional condition if fetching all chunks. Otherwise, use an
493-
* equality condition for one chunk, and a range condition otherwise.
494-
*/
495-
if (startchunk==0&&endchunk==totalchunks-1)
496-
nscankeys=1;
497-
elseif (startchunk==endchunk)
498-
{
499-
ScanKeyInit(&toastkey[1],
500-
(AttrNumber)2,
501-
BTEqualStrategyNumber,F_INT4EQ,
502-
Int32GetDatum(startchunk));
503-
nscankeys=2;
504-
}
505-
else
506-
{
507-
ScanKeyInit(&toastkey[1],
508-
(AttrNumber)2,
509-
BTGreaterEqualStrategyNumber,F_INT4GE,
510-
Int32GetDatum(startchunk));
511-
ScanKeyInit(&toastkey[2],
512-
(AttrNumber)2,
513-
BTLessEqualStrategyNumber,F_INT4LE,
514-
Int32GetDatum(endchunk));
515-
nscankeys=3;
516-
}
517-
518-
/* Prepare for scan */
519-
init_toast_snapshot(&SnapshotToast);
520-
toastscan=systable_beginscan_ordered(toastrel,toastidxs[validIndex],
521-
&SnapshotToast,nscankeys,toastkey);
522-
523-
/*
524-
* Read the chunks by index
525-
*
526-
* The index is on (valueid, chunkidx) so they will come in order
527-
*/
528-
expectedchunk=startchunk;
529-
while ((ttup=systable_getnext_ordered(toastscan,ForwardScanDirection))!=NULL)
530-
{
531-
int32curchunk;
532-
Pointerchunk;
533-
boolisnull;
534-
char*chunkdata;
535-
int32chunksize;
536-
int32expected_size;
537-
int32chcpystrt;
538-
int32chcpyend;
539-
540-
/*
541-
* Have a chunk, extract the sequence number and the data
542-
*/
543-
curchunk=DatumGetInt32(fastgetattr(ttup,2,toasttupDesc,&isnull));
544-
Assert(!isnull);
545-
chunk=DatumGetPointer(fastgetattr(ttup,3,toasttupDesc,&isnull));
546-
Assert(!isnull);
547-
if (!VARATT_IS_EXTENDED(chunk))
548-
{
549-
chunksize=VARSIZE(chunk)-VARHDRSZ;
550-
chunkdata=VARDATA(chunk);
551-
}
552-
elseif (VARATT_IS_SHORT(chunk))
553-
{
554-
/* could happen due to heap_form_tuple doing its thing */
555-
chunksize=VARSIZE_SHORT(chunk)-VARHDRSZ_SHORT;
556-
chunkdata=VARDATA_SHORT(chunk);
557-
}
558-
else
559-
{
560-
/* should never happen */
561-
elog(ERROR,"found toasted toast chunk for toast value %u in %s",
562-
valueid,RelationGetRelationName(toastrel));
563-
chunksize=0;/* keep compiler quiet */
564-
chunkdata=NULL;
565-
}
566-
567-
/*
568-
* Some checks on the data we've found
569-
*/
570-
if (curchunk!=expectedchunk)
571-
ereport(ERROR,
572-
(errcode(ERRCODE_DATA_CORRUPTED),
573-
errmsg_internal("unexpected chunk number %d (expected %d) for toast value %u in %s",
574-
curchunk,expectedchunk,valueid,
575-
RelationGetRelationName(toastrel))));
576-
if (curchunk>endchunk)
577-
ereport(ERROR,
578-
(errcode(ERRCODE_DATA_CORRUPTED),
579-
errmsg_internal("unexpected chunk number %d (out of range %d..%d) for toast value %u in %s",
580-
curchunk,
581-
startchunk,endchunk,valueid,
582-
RelationGetRelationName(toastrel))));
583-
expected_size=curchunk<totalchunks-1 ?TOAST_MAX_CHUNK_SIZE
584-
:attrsize- ((totalchunks-1)*TOAST_MAX_CHUNK_SIZE);
585-
if (chunksize!=expected_size)
586-
ereport(ERROR,
587-
(errcode(ERRCODE_DATA_CORRUPTED),
588-
errmsg_internal("unexpected chunk size %d (expected %d) in chunk %d of %d for toast value %u in %s",
589-
chunksize,expected_size,
590-
curchunk,totalchunks,valueid,
591-
RelationGetRelationName(toastrel))));
592-
593-
/*
594-
* Copy the data into proper place in our result
595-
*/
596-
chcpystrt=0;
597-
chcpyend=chunksize-1;
598-
if (curchunk==startchunk)
599-
chcpystrt=sliceoffset %TOAST_MAX_CHUNK_SIZE;
600-
if (curchunk==endchunk)
601-
chcpyend= (sliceoffset+slicelength-1) %TOAST_MAX_CHUNK_SIZE;
602-
603-
memcpy(VARDATA(result)+
604-
(curchunk*TOAST_MAX_CHUNK_SIZE-sliceoffset)+chcpystrt,
605-
chunkdata+chcpystrt,
606-
(chcpyend-chcpystrt)+1);
607-
608-
expectedchunk++;
609-
}
610-
611-
/*
612-
* Final checks that we successfully fetched the datum
613-
*/
614-
if (expectedchunk!= (endchunk+1))
615-
ereport(ERROR,
616-
(errcode(ERRCODE_DATA_CORRUPTED),
617-
errmsg_internal("missing chunk number %d for toast value %u in %s",
618-
expectedchunk,valueid,
619-
RelationGetRelationName(toastrel))));
620-
621-
/* End scan and close indexes. */
622-
systable_endscan_ordered(toastscan);
623-
toast_close_indexes(toastidxs,num_indexes,AccessShareLock);
624-
}
625-
626439
/* ----------
627440
* toast_decompress_datum -
628441
*

‎src/backend/access/heap/heapam_handler.c‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2545,6 +2545,7 @@ static const TableAmRoutine heapam_methods = {
25452545
.relation_size=table_block_relation_size,
25462546
.relation_needs_toast_table=heapam_relation_needs_toast_table,
25472547
.relation_toast_am=heapam_relation_toast_am,
2548+
.relation_fetch_toast_slice=heap_fetch_toast_slice,
25482549

25492550
.relation_estimate_size=heapam_estimate_rel_size,
25502551

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