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Commit642107d

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Avoid unnecessary lseek() calls by cleanups in md.c. mdfd_lstbcnt was
not being consulted anywhere, so remove it and remove the _mdnblocks()calls that were used to set it. Change smgrextend interface to pass inthe target block number (ie, current file length) --- the caller alwaysknows this already, having already done smgrnblocks(), so it's silly todo it over again inside mdextend. Net result: extension of a file nowtakes one lseek(SEEK_END) and a write(), not three lseeks and a write.
1 parenta26ad8a commit642107d

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6 files changed

+127
-104
lines changed

6 files changed

+127
-104
lines changed

‎src/backend/commands/sequence.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/commands/sequence.c,v 1.54 2001/04/04 15:43:25 vadim Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/commands/sequence.c,v 1.55 2001/05/10 20:38:49 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -569,7 +569,7 @@ read_info(char *caller, SeqTable elm, Buffer *buf)
569569
sequence_magic*sm;
570570
Form_pg_sequenceseq;
571571

572-
if (RelationGetNumberOfBlocks(elm->rel)!=1)
572+
if (elm->rel->rd_nblocks>1)
573573
elog(ERROR,"%s.%s: invalid number of blocks in sequence",
574574
elm->name,caller);
575575

‎src/backend/storage/buffer/bufmgr.c

Lines changed: 29 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.109 2001/03/22 03:59:44 momjian Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.110 2001/05/10 20:38:49 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -173,9 +173,9 @@ ReadBufferWithBufferLock(Relation reln,
173173
boolbufferLockHeld)
174174
{
175175
BufferDesc*bufHdr;
176-
intextend;/* extending the file by one block */
177176
intstatus;
178177
boolfound;
178+
boolextend;/* extending the file by one block */
179179
boolisLocalBuf;
180180

181181
extend= (blockNum==P_NEW);
@@ -207,21 +207,13 @@ ReadBufferWithBufferLock(Relation reln,
207207
/* if it's already in the buffer pool, we're done */
208208
if (found)
209209
{
210-
211210
/*
212-
*This happens when a bogusbuffer wasreturned previously and is
213-
*floating around in the buffer pool.A routine calling this
214-
*would want this extended.
211+
*Could see found && extend if abuffer wasalready created for
212+
*the next page position, but then smgrextend failed to write
213+
*the page. Must fall through and try to extend file again.
215214
*/
216-
if (extend)
217-
{
218-
/* new buffers are zero-filled */
219-
MemSet((char*)MAKE_PTR(bufHdr->data),0,BLCKSZ);
220-
smgrextend(DEFAULT_SMGR,reln,
221-
(char*)MAKE_PTR(bufHdr->data));
222-
}
223-
returnBufferDescriptorGetBuffer(bufHdr);
224-
215+
if (!extend)
216+
returnBufferDescriptorGetBuffer(bufHdr);
225217
}
226218

227219
/*
@@ -232,17 +224,25 @@ ReadBufferWithBufferLock(Relation reln,
232224
{
233225
/* new buffers are zero-filled */
234226
MemSet((char*)MAKE_PTR(bufHdr->data),0,BLCKSZ);
235-
status=smgrextend(DEFAULT_SMGR,reln,
227+
status=smgrextend(DEFAULT_SMGR,reln,bufHdr->tag.blockNum,
236228
(char*)MAKE_PTR(bufHdr->data));
237229
}
238230
else
239231
{
240-
status=smgrread(DEFAULT_SMGR,reln,blockNum,
232+
status=smgrread(DEFAULT_SMGR,reln,bufHdr->tag.blockNum,
241233
(char*)MAKE_PTR(bufHdr->data));
242234
}
243235

244236
if (isLocalBuf)
237+
{
238+
/* No shared buffer state to update... */
239+
if (status==SM_FAIL)
240+
{
241+
bufHdr->flags |=BM_IO_ERROR;
242+
returnInvalidBuffer;
243+
}
245244
returnBufferDescriptorGetBuffer(bufHdr);
245+
}
246246

247247
/* lock buffer manager again to update IO IN PROGRESS */
248248
SpinAcquire(BufMgrLock);
@@ -302,13 +302,11 @@ BufferAlloc(Relation reln,
302302
*buf2;
303303
BufferTagnewTag;/* identity of requested block */
304304
boolinProgress;/* buffer undergoing IO */
305-
boolnewblock= FALSE;
306305

307306
/* create a new tag so we can lookup the buffer */
308307
/* assume that the relation is already open */
309308
if (blockNum==P_NEW)
310309
{
311-
newblock= TRUE;
312310
blockNum=smgrnblocks(DEFAULT_SMGR,reln);
313311
}
314312

@@ -1102,7 +1100,8 @@ BufferReplace(BufferDesc *bufHdr)
11021100

11031101
/*
11041102
* RelationGetNumberOfBlocks
1105-
*Returns the buffer descriptor associated with a page in a relation.
1103+
*Determines the current number of pages in the relation.
1104+
*Side effect: relation->rd_nblocks is updated.
11061105
*
11071106
* Note:
11081107
*XXX may fail for huge relations.
@@ -1112,9 +1111,16 @@ BufferReplace(BufferDesc *bufHdr)
11121111
BlockNumber
11131112
RelationGetNumberOfBlocks(Relationrelation)
11141113
{
1115-
return ((relation->rd_myxactonly) ?relation->rd_nblocks :
1116-
((relation->rd_rel->relkind==RELKIND_VIEW) ?0 :
1117-
smgrnblocks(DEFAULT_SMGR,relation)));
1114+
/*
1115+
* relation->rd_nblocks should be accurate already if the relation
1116+
* is myxactonly. (XXX how safe is that really?) Don't call smgr
1117+
* on a view, either.
1118+
*/
1119+
if (relation->rd_rel->relkind==RELKIND_VIEW)
1120+
relation->rd_nblocks=0;
1121+
elseif (!relation->rd_myxactonly)
1122+
relation->rd_nblocks=smgrnblocks(DEFAULT_SMGR,relation);
1123+
returnrelation->rd_nblocks;
11181124
}
11191125

11201126
/* ---------------------------------------------------------------------

‎src/backend/storage/smgr/md.c

Lines changed: 75 additions & 65 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/storage/smgr/md.c,v 1.83 2001/04/02 23:20:24 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/storage/smgr/md.c,v 1.84 2001/05/1020:38:49 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -54,10 +54,9 @@ typedef struct _MdfdVec
5454
intmdfd_flags;/* fd status flags */
5555

5656
/* these are the assigned bits in mdfd_flags: */
57-
#defineMDFD_FREE(1 << 0)/* unused entry */
57+
#defineMDFD_FREE(1 << 0)/* unused entry */
5858

59-
intmdfd_lstbcnt;/* most recent block count */
60-
intmdfd_nextFree;/* next free vector */
59+
intmdfd_nextFree;/* link to next freelist member, if free */
6160
#ifndefLET_OS_MANAGE_FILESIZE
6261
struct_MdfdVec*mdfd_chain;/* for large relations */
6362
#endif
@@ -164,7 +163,6 @@ mdcreate(Relation reln)
164163

165164
Md_fdvec[vfd].mdfd_vfd=fd;
166165
Md_fdvec[vfd].mdfd_flags= (uint16)0;
167-
Md_fdvec[vfd].mdfd_lstbcnt=0;
168166
#ifndefLET_OS_MANAGE_FILESIZE
169167
Md_fdvec[vfd].mdfd_chain= (MdfdVec*)NULL;
170168
#endif
@@ -225,52 +223,69 @@ mdunlink(RelFileNode rnode)
225223
/*
226224
*mdextend() -- Add a block to the specified relation.
227225
*
226+
*The semantics are basically the same as mdwrite(): write at the
227+
*specified position. However, we are expecting to extend the
228+
*relation (ie, blocknum is the current EOF), and so in case of
229+
*failure we clean up by truncating.
230+
*
228231
*This routine returns SM_FAIL or SM_SUCCESS, with errno set as
229232
*appropriate.
233+
*
234+
* Note: this routine used to call mdnblocks() to get the block position
235+
* to write at, but that's pretty silly since the caller needs to know where
236+
* the block will be written, and accordingly must have done mdnblocks()
237+
* already. Might as well pass in the position and save a seek.
230238
*/
231239
int
232-
mdextend(Relationreln,char*buffer)
240+
mdextend(Relationreln,BlockNumberblocknum,char*buffer)
233241
{
234-
longpos,
235-
nbytes;
236-
intnblocks;
242+
longseekpos;
243+
intnbytes;
237244
MdfdVec*v;
238245

239-
nblocks=mdnblocks(reln);
240-
v=_mdfd_getseg(reln,nblocks);
246+
v=_mdfd_getseg(reln,blocknum);
241247

242-
if ((pos=FileSeek(v->mdfd_vfd,0L,SEEK_END))<0)
243-
returnSM_FAIL;
248+
#ifndefLET_OS_MANAGE_FILESIZE
249+
seekpos= (long) (BLCKSZ* (blocknum %RELSEG_SIZE));
250+
#ifdefDIAGNOSTIC
251+
if (seekpos >=BLCKSZ*RELSEG_SIZE)
252+
elog(FATAL,"seekpos too big!");
253+
#endif
254+
#else
255+
seekpos= (long) (BLCKSZ* (blocknum));
256+
#endif
244257

245-
if (pos %BLCKSZ!=0)/* the last block is incomplete */
246-
{
247-
pos-=pos %BLCKSZ;
248-
if (FileSeek(v->mdfd_vfd,pos,SEEK_SET)<0)
249-
returnSM_FAIL;
250-
}
258+
/*
259+
* Note: because caller obtained blocknum by calling mdnblocks, which
260+
* did a seek(SEEK_END), this seek is often redundant and will be
261+
* optimized away by fd.c. It's not redundant, however, if there is a
262+
* partial page at the end of the file. In that case we want to try to
263+
* overwrite the partial page with a full page. It's also not redundant
264+
* if bufmgr.c had to dump another buffer of the same file to make room
265+
* for the new page's buffer.
266+
*/
267+
if (FileSeek(v->mdfd_vfd,seekpos,SEEK_SET)!=seekpos)
268+
returnSM_FAIL;
251269

252270
if ((nbytes=FileWrite(v->mdfd_vfd,buffer,BLCKSZ))!=BLCKSZ)
253271
{
254272
if (nbytes>0)
255273
{
256-
FileTruncate(v->mdfd_vfd,pos);
257-
FileSeek(v->mdfd_vfd,pos,SEEK_SET);
274+
intsave_errno=errno;
275+
276+
/* Remove the partially-written page */
277+
FileTruncate(v->mdfd_vfd,seekpos);
278+
FileSeek(v->mdfd_vfd,seekpos,SEEK_SET);
279+
errno=save_errno;
258280
}
259281
returnSM_FAIL;
260282
}
261283

262-
/* try to keep the last block count current, though it's just a hint */
263284
#ifndefLET_OS_MANAGE_FILESIZE
264-
if ((v->mdfd_lstbcnt= (++nblocks %RELSEG_SIZE))==0)
265-
v->mdfd_lstbcnt=RELSEG_SIZE;
266-
267285
#ifdefDIAGNOSTIC
268-
if (_mdnblocks(v->mdfd_vfd,BLCKSZ)>RELSEG_SIZE
269-
||v->mdfd_lstbcnt>RELSEG_SIZE)
286+
if (_mdnblocks(v->mdfd_vfd,BLCKSZ)>RELSEG_SIZE)
270287
elog(FATAL,"segment too big!");
271288
#endif
272-
#else
273-
v->mdfd_lstbcnt=++nblocks;
274289
#endif
275290

276291
returnSM_SUCCESS;
@@ -319,12 +334,11 @@ mdopen(Relation reln)
319334

320335
Md_fdvec[vfd].mdfd_vfd=fd;
321336
Md_fdvec[vfd].mdfd_flags= (uint16)0;
322-
Md_fdvec[vfd].mdfd_lstbcnt=_mdnblocks(fd,BLCKSZ);
323337
#ifndefLET_OS_MANAGE_FILESIZE
324338
Md_fdvec[vfd].mdfd_chain= (MdfdVec*)NULL;
325339

326340
#ifdefDIAGNOSTIC
327-
if (Md_fdvec[vfd].mdfd_lstbcnt>RELSEG_SIZE)
341+
if (_mdnblocks(fd,BLCKSZ)>RELSEG_SIZE)
328342
elog(FATAL,"segment too big on relopen!");
329343
#endif
330344
#endif
@@ -440,9 +454,12 @@ mdread(Relation reln, BlockNumber blocknum, char *buffer)
440454
status=SM_SUCCESS;
441455
if ((nbytes=FileRead(v->mdfd_vfd,buffer,BLCKSZ))!=BLCKSZ)
442456
{
443-
if (nbytes==0)
444-
MemSet(buffer,0,BLCKSZ);
445-
elseif (blocknum==0&&nbytes>0&&mdnblocks(reln)==0)
457+
/*
458+
* If we are at EOF, return zeroes without complaining.
459+
* (XXX Is this still necessary/a good idea??)
460+
*/
461+
if (nbytes==0||
462+
(nbytes>0&&mdnblocks(reln)==blocknum))
446463
MemSet(buffer,0,BLCKSZ);
447464
else
448465
status=SM_FAIL;
@@ -459,7 +476,6 @@ mdread(Relation reln, BlockNumber blocknum, char *buffer)
459476
int
460477
mdwrite(Relationreln,BlockNumberblocknum,char*buffer)
461478
{
462-
intstatus;
463479
longseekpos;
464480
MdfdVec*v;
465481

@@ -478,11 +494,10 @@ mdwrite(Relation reln, BlockNumber blocknum, char *buffer)
478494
if (FileSeek(v->mdfd_vfd,seekpos,SEEK_SET)!=seekpos)
479495
returnSM_FAIL;
480496

481-
status=SM_SUCCESS;
482497
if (FileWrite(v->mdfd_vfd,buffer,BLCKSZ)!=BLCKSZ)
483-
status=SM_FAIL;
498+
returnSM_FAIL;
484499

485-
returnstatus;
500+
returnSM_SUCCESS;
486501
}
487502

488503
/*
@@ -662,31 +677,29 @@ mdnblocks(Relation reln)
662677
nblocks=_mdnblocks(v->mdfd_vfd,BLCKSZ);
663678
if (nblocks>RELSEG_SIZE)
664679
elog(FATAL,"segment too big in mdnblocks!");
665-
v->mdfd_lstbcnt=nblocks;
666-
if (nblocks==RELSEG_SIZE)
667-
{
668-
segno++;
680+
if (nblocks<RELSEG_SIZE)
681+
return (segno*RELSEG_SIZE)+nblocks;
682+
/*
683+
* If segment is exactly RELSEG_SIZE, advance to next one.
684+
*/
685+
segno++;
669686

687+
if (v->mdfd_chain== (MdfdVec*)NULL)
688+
{
689+
/*
690+
* Because we pass O_CREAT, we will create the next
691+
* segment (with zero length) immediately, if the last
692+
* segment is of length REL_SEGSIZE. This is unnecessary
693+
* but harmless, and testing for the case would take more
694+
* cycles than it seems worth.
695+
*/
696+
v->mdfd_chain=_mdfd_openseg(reln,segno,O_CREAT);
670697
if (v->mdfd_chain== (MdfdVec*)NULL)
671-
{
672-
673-
/*
674-
* Because we pass O_CREAT, we will create the next
675-
* segment (with zero length) immediately, if the last
676-
* segment is of length REL_SEGSIZE. This is unnecessary
677-
* but harmless, and testing for the case would take more
678-
* cycles than it seems worth.
679-
*/
680-
v->mdfd_chain=_mdfd_openseg(reln,segno,O_CREAT);
681-
if (v->mdfd_chain== (MdfdVec*)NULL)
682-
elog(ERROR,"cannot count blocks for %s -- open failed: %m",
683-
RelationGetRelationName(reln));
684-
}
685-
686-
v=v->mdfd_chain;
698+
elog(ERROR,"cannot count blocks for %s -- open failed: %m",
699+
RelationGetRelationName(reln));
687700
}
688-
else
689-
return (segno*RELSEG_SIZE)+nblocks;
701+
702+
v=v->mdfd_chain;
690703
}
691704
#else
692705
return_mdnblocks(v->mdfd_vfd,BLCKSZ);
@@ -761,7 +774,6 @@ mdtruncate(Relation reln, int nblocks)
761774

762775
if (FileTruncate(v->mdfd_vfd,lastsegblocks*BLCKSZ)<0)
763776
return-1;
764-
v->mdfd_lstbcnt=lastsegblocks;
765777
v=v->mdfd_chain;
766778
ov->mdfd_chain= (MdfdVec*)NULL;
767779
}
@@ -779,7 +791,6 @@ mdtruncate(Relation reln, int nblocks)
779791
#else
780792
if (FileTruncate(v->mdfd_vfd,nblocks*BLCKSZ)<0)
781793
return-1;
782-
v->mdfd_lstbcnt=nblocks;
783794
#endif
784795

785796
returnnblocks;
@@ -958,13 +969,12 @@ _mdfd_openseg(Relation reln, int segno, int oflags)
958969
/* fill the entry */
959970
v->mdfd_vfd=fd;
960971
v->mdfd_flags= (uint16)0;
961-
v->mdfd_lstbcnt=_mdnblocks(fd,BLCKSZ);
962972
#ifndefLET_OS_MANAGE_FILESIZE
963973
v->mdfd_chain= (MdfdVec*)NULL;
964974

965975
#ifdefDIAGNOSTIC
966-
if (v->mdfd_lstbcnt>RELSEG_SIZE)
967-
elog(FATAL,"segment too big onopen!");
976+
if (_mdnblocks(fd,BLCKSZ)>RELSEG_SIZE)
977+
elog(FATAL,"segment too big onopenseg!");
968978
#endif
969979
#endif
970980

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