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Commita62d839

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Repair Large Object bugs demonstrated by Ian Grant's example. inv_write
was inappropriately relying on rel->rd_nblocks to tell if the LO isempty (apparently a hack to get around a long-dead index bug), causingmisbehavior on a written-but-never-vacuumed LO. Also, inv_read failedto cope gracefully with 'holes' (unwritten regions) in the object.
1 parent946e80c commita62d839

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1 file changed

+33
-23
lines changed

1 file changed

+33
-23
lines changed

‎src/backend/storage/large_object/inv_api.c

Lines changed: 33 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $Header: /cvsroot/pgsql/src/backend/storage/large_object/inv_api.c,v 1.69 2000/06/0507:28:45 tgl Exp $
12+
* $Header: /cvsroot/pgsql/src/backend/storage/large_object/inv_api.c,v 1.70 2000/06/15 06:07:34 tgl Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -187,6 +187,7 @@ inv_create(int flags)
187187
retval->idesc=RelationGetDescr(indr);
188188
retval->offset=retval->lowbyte=retval->highbyte=0;
189189
ItemPointerSetInvalid(&(retval->htid));
190+
retval->flags=0;
190191

191192
if (flags&INV_WRITE)
192193
{
@@ -198,7 +199,7 @@ inv_create(int flags)
198199
LockRelation(r,ShareLock);
199200
retval->flags=IFS_RDLOCK;
200201
}
201-
retval->flags |=IFS_ATEOF;
202+
retval->flags |=IFS_ATEOF;/* since we know the object is empty */
202203

203204
returnretval;
204205
}
@@ -235,6 +236,7 @@ inv_open(Oid lobjId, int flags)
235236
retval->idesc=RelationGetDescr(indrel);
236237
retval->offset=retval->lowbyte=retval->highbyte=0;
237238
ItemPointerSetInvalid(&(retval->htid));
239+
retval->flags=0;
238240

239241
if (flags&INV_WRITE)
240242
{
@@ -373,14 +375,8 @@ inv_seek(LargeObjectDesc *obj_desc, int offset, int whence)
373375
if (whence==SEEK_CUR)
374376
{
375377
offset+=obj_desc->offset;/* calculate absolute position */
376-
returninv_seek(obj_desc,offset,SEEK_SET);
377378
}
378-
379-
/*
380-
* if you seek past the end (offset > 0) I have no clue what happens
381-
* :-( B.L. 9/1/93
382-
*/
383-
if (whence==SEEK_END)
379+
elseif (whence==SEEK_END)
384380
{
385381
/* need read lock for getsize */
386382
if (!(obj_desc->flags&IFS_RDLOCK))
@@ -391,8 +387,8 @@ inv_seek(LargeObjectDesc *obj_desc, int offset, int whence)
391387
offset+=_inv_getsize(obj_desc->heap_r,
392388
obj_desc->hdesc,
393389
obj_desc->index_r);
394-
returninv_seek(obj_desc,offset,SEEK_SET);
395390
}
391+
/* now we can assume that the operation is SEEK_SET */
396392

397393
/*
398394
* Whenever we do a seek, we turn off the EOF flag bit to force
@@ -416,17 +412,13 @@ inv_seek(LargeObjectDesc *obj_desc, int offset, int whence)
416412
* stores the offset of the last byte that appears on it, and we have
417413
* an index on this.
418414
*/
419-
420-
421-
/* right now, just assume that the operation is SEEK_SET */
422415
if (obj_desc->iscan!= (IndexScanDesc)NULL)
423416
{
424417
d=Int32GetDatum(offset);
425418
btmovescan(obj_desc->iscan,d);
426419
}
427420
else
428421
{
429-
430422
ScanKeyEntryInitialize(&skey,0x0,1,F_INT4GE,
431423
Int32GetDatum(offset));
432424

@@ -489,9 +481,27 @@ inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes)
489481

490482
/* copy the data from this block into the buffer */
491483
d=heap_getattr(&tuple,2,obj_desc->hdesc,&isNull);
484+
fsblock= (structvarlena*)DatumGetPointer(d);
492485
ReleaseBuffer(buffer);
493486

494-
fsblock= (structvarlena*)DatumGetPointer(d);
487+
/*
488+
* If block starts beyond current seek point, then we are looking
489+
* at a "hole" (unwritten area) in the object. Return zeroes for
490+
* the "hole".
491+
*/
492+
if (obj_desc->offset<obj_desc->lowbyte)
493+
{
494+
intnzeroes=obj_desc->lowbyte-obj_desc->offset;
495+
496+
if (nzeroes> (nbytes-nread))
497+
nzeroes= (nbytes-nread);
498+
MemSet(buf,0,nzeroes);
499+
buf+=nzeroes;
500+
nread+=nzeroes;
501+
obj_desc->offset+=nzeroes;
502+
if (nread >=nbytes)
503+
break;
504+
}
495505

496506
off=obj_desc->offset-obj_desc->lowbyte;
497507
ncopy=obj_desc->highbyte-obj_desc->offset+1;
@@ -537,14 +547,11 @@ inv_write(LargeObjectDesc *obj_desc, char *buf, int nbytes)
537547
Bufferbuffer;
538548

539549
/*
540-
* Fetch the current inversion file system block. If the class
541-
* storing the inversion file is empty, we don't want to do an
542-
* index lookup, since index lookups choke on empty files (should
543-
* be fixed someday).
550+
* Fetch the current inversion file system block. We can skip
551+
* the work if we already know we are at EOF.
544552
*/
545553

546-
if ((obj_desc->flags&IFS_ATEOF)
547-
||obj_desc->heap_r->rd_nblocks==0)
554+
if (obj_desc->flags&IFS_ATEOF)
548555
tuple.t_data=NULL;
549556
else
550557
inv_fetchtup(obj_desc,&tuple,&buffer);
@@ -659,6 +666,7 @@ inv_fetchtup(LargeObjectDesc *obj_desc, HeapTuple tuple, Buffer *buffer)
659666
}
660667
else
661668
index_rescan(obj_desc->iscan, false,&skey);
669+
662670
do
663671
{
664672
res=index_getnext(obj_desc->iscan,ForwardScanDirection);
@@ -1149,7 +1157,8 @@ inv_indextup(LargeObjectDesc *obj_desc, HeapTuple tuple)
11491157
pfree(res);
11501158
}
11511159

1152-
/*
1160+
#ifdefNOT_USED
1161+
11531162
staticvoid
11541163
DumpPage(Pagepage,intblkno)
11551164
{
@@ -1239,7 +1248,8 @@ ItemPointerFormExternal(ItemPointer pointer)
12391248

12401249
returnitemPointerString;
12411250
}
1242-
*/
1251+
1252+
#endif
12431253

12441254
staticint
12451255
_inv_getsize(Relationhreln,TupleDeschdesc,Relationireln)

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