Re: [HACKERS] large objects failing (hpux10.20 sparc/solaris 2.6, gcc 2.8.1)

> Postgres 6.4.2, gcc 2.8.1, hpux 10.20 and Sparc/Solaris 2.6
> (All debugging attempts were on the hpux machine, but the symptom also
> occurs on the Solaris box.  Also tried the latest (feb 18) snapshot
> on the hpux box, symptom still occurs.)
> 
> I was installing the perl DBD::Pg module, but it fails the large object 
> test.  To make sure it wasn't just an issue with perl (or the module),
> I compiled and ran src/test/examples/testlo, and it also fails.
> (testlo2 also has failed in the past, although I didn't use it for any
> of my current debugging attempts.)
> 
> (In case there's any question, I created a database, and then created
> a short text file called /tmp/gaga (ok, so I used the same file that 
> the perl module created for the perl test; you caught me) with one line of
> text.  Then I do:
> 
> ./testlo ronfoo /tmp/gaga /tmp/gaga1
> 
> which fails complaining that there was an error reading the file (which
> actually is misleading-- the error actually is in writing to the new
> large object).
> 
> (after you do this, you must drop the database and recreate it before you
> run testlo again, otherwise you get errors about creating the xinv##### 
> "object".)

I made patches for 6.4.2 a week ago to fix problems of lobj reported
by another user. I'm not sure if his problem was solved or not, since
I got no reply from him. Anyway, with the patch, lotest.c runs fine on
my LinuxPPC box. More over, following commented out part of testlo.c
now passes without any problem (I guess these were commented out
becasue overwriting lobj did not work).

/*printf("\tas large object %d.\n", lobjOid);
printf("picking out bytes 1000-2000 of the large object\n");pickout(conn, lobjOid, 1000, 1000);
printf("overwriting bytes 1000-2000 of the large object with X's\n");overwrite(conn, lobjOid, 1000, 1000);
*/

Tatsuo Ishii
------------------------------ cut here -------------------------------
*** postgresql-6.4.2/src/backend/storage/large_object/inv_api.c.orig    Sun Dec 13 14:08:19 1998
--- postgresql-6.4.2/src/backend/storage/large_object/inv_api.c    Fri Feb 12 20:21:05 1999
***************
*** 545,555 ****             tuplen = inv_wrnew(obj_desc, buf, nbytes - nwritten);         else         {
!             if (obj_desc->offset > obj_desc->highbyte)                 tuplen = inv_wrnew(obj_desc, buf, nbytes -
nwritten);            else                 tuplen = inv_wrold(obj_desc, buf, nbytes - nwritten, tuple, buffer);
 
!             ReleaseBuffer(buffer);         }          /* move pointers past the amount we just wrote */
--- 545,561 ----             tuplen = inv_wrnew(obj_desc, buf, nbytes - nwritten);         else         {
!                   if (obj_desc->offset > obj_desc->highbyte) {                 tuplen = inv_wrnew(obj_desc, buf,
nbytes- nwritten);
 
+                 ReleaseBuffer(buffer);
+             }             else                 tuplen = inv_wrold(obj_desc, buf, nbytes - nwritten, tuple, buffer);
!             /* inv_wrold() has already issued WriteBuffer()
!                which has decremented local reference counter
!                (LocalRefCount). So we should not call
!                ReleaseBuffer() here. -- Tatsuo 99/2/4
!             ReleaseBuffer(buffer); */         }          /* move pointers past the amount we just wrote */
***************
*** 624,648 ****         || obj_desc->offset < obj_desc->lowbyte         || !ItemPointerIsValid(&(obj_desc->htid)))
{         /* initialize scan key if not done */         if (obj_desc->iscan == (IndexScanDesc) NULL)         {
 
-             ScanKeyData skey;
-              /*              * As scan index may be prematurely closed (on commit), we              * must use object
currentoffset (was 0) to reinitialize the              * entry [ PA ].              */
 
-             ScanKeyEntryInitialize(&skey, 0x0, 1, F_INT4GE,
-                                    Int32GetDatum(obj_desc->offset));             obj_desc->iscan =
index_beginscan(obj_desc->index_r,                                (bool) 0, (uint16) 1,
&skey);        }
 
-          do         {             res = index_getnext(obj_desc->iscan, ForwardScanDirection);
--- 630,655 ----         || obj_desc->offset < obj_desc->lowbyte         || !ItemPointerIsValid(&(obj_desc->htid)))
{
+         ScanKeyData skey;
+ 
+         ScanKeyEntryInitialize(&skey, 0x0, 1, F_INT4GE,
+                        Int32GetDatum(obj_desc->offset));          /* initialize scan key if not done */         if
(obj_desc->iscan== (IndexScanDesc) NULL)         {             /*              * As scan index may be prematurely
closed(on commit), we              * must use object current offset (was 0) to reinitialize the              * entry [
PA].              */             obj_desc->iscan =                 index_beginscan(obj_desc->index_r,
             (bool) 0, (uint16) 1,                                 &skey);
 
+         } else {
+             index_rescan(obj_desc->iscan, false, &skey);         }         do         {             res =
index_getnext(obj_desc->iscan,ForwardScanDirection);
 
***************
*** 666,672 ****             tuple = heap_fetch(obj_desc->heap_r, SnapshotNow,
&res->heap_iptr,buffer);             pfree(res);
 
!         } while (tuple == (HeapTuple) NULL);          /* remember this tid -- we may need it for later reads/writes
*/         ItemPointerCopy(&tuple->t_ctid, &obj_desc->htid);
 
--- 673,679 ----             tuple = heap_fetch(obj_desc->heap_r, SnapshotNow,
&res->heap_iptr,buffer);             pfree(res);
 
!         } while (!HeapTupleIsValid(tuple));          /* remember this tid -- we may need it for later reads/writes */
        ItemPointerCopy(&tuple->t_ctid, &obj_desc->htid);
 
***************
*** 675,680 ****
--- 682,691 ----     {         tuple = heap_fetch(obj_desc->heap_r, SnapshotNow,
&(obj_desc->htid),buffer);
 
+         if (!HeapTupleIsValid(tuple)) {
+           elog(ERROR,
+                "inv_fetchtup: heap_fetch failed");
+         }     }      /*
***************
*** 746,757 ****      nblocks = RelationGetNumberOfBlocks(hr); 
!     if (nblocks > 0)         buffer = ReadBuffer(hr, nblocks - 1);
!     else         buffer = ReadBuffer(hr, P_NEW);
! 
!     page = BufferGetPage(buffer);      /*      * If the last page is too small to hold all the data, and it's too
--- 757,771 ----      nblocks = RelationGetNumberOfBlocks(hr); 
!     if (nblocks > 0) {         buffer = ReadBuffer(hr, nblocks - 1);
!         page = BufferGetPage(buffer);
!     }
!     else {         buffer = ReadBuffer(hr, P_NEW);
!         page = BufferGetPage(buffer);
!         PageInit(page, BufferGetPageSize(buffer), 0);
!     }      /*      * If the last page is too small to hold all the data, and it's too
***************
*** 865,876 ****          nblocks = RelationGetNumberOfBlocks(hr); 
!         if (nblocks > 0)             newbuf = ReadBuffer(hr, nblocks - 1);
!         else             newbuf = ReadBuffer(hr, P_NEW); 
-         newpage = BufferGetPage(newbuf);         freespc = IFREESPC(newpage);          /*
--- 879,894 ----          nblocks = RelationGetNumberOfBlocks(hr); 
!         if (nblocks > 0) {             newbuf = ReadBuffer(hr, nblocks - 1);
!             newpage = BufferGetPage(newbuf);
!         }
!         else {             newbuf = ReadBuffer(hr, P_NEW);
+             newpage = BufferGetPage(newbuf);
+             PageInit(newpage, BufferGetPageSize(newbuf), 0);
+         }          freespc = IFREESPC(newpage);          /*
***************
*** 973,978 ****
--- 991,999 ----     WriteBuffer(buffer);     if (newbuf != buffer)         WriteBuffer(newbuf);
+ 
+     /* Tuple id is no longer valid */
+     ItemPointerSetInvalid(&(obj_desc->htid));      /* done */     return nwritten;