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Remove unnecessary calls of FlushRelationBuffers: there is no need
to write out data that we are about to tell the filesystem to drop. smgr_internal_unlink already had a DropRelFileNodeBuffers call to get rid of dead buffers without a write after it's no longer possible to roll back the deleting transaction. Adding a similar call in smgrtruncate simplifies callers and makes the overall division of labor clearer. This patch removes the former behavior that VACUUM would write all dirty buffers of a relation unconditionally.
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10 files changed

+92
-237
lines changed

10 files changed

+92
-237
lines changed

‎src/backend/access/nbtree/nbtree.c‎

Lines changed: 1 addition & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -12,7 +12,7 @@
1212
* Portions Copyright (c) 1994, Regents of the University of California
1313
*
1414
* IDENTIFICATION
15-
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.124 2004/12/31 21:59:22 pgsql Exp $
15+
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.125 2005/03/20 22:00:50 tgl Exp $
1616
*
1717
*-------------------------------------------------------------------------
1818
*/
@@ -772,17 +772,6 @@ btvacuumcleanup(PG_FUNCTION_ARGS)
772772
{
773773
/*
774774
* Okay to truncate.
775-
*
776-
* First, flush any shared buffers for the blocks we intend to
777-
* delete. FlushRelationBuffers is a bit more than we need
778-
* for this, since it will also write out dirty buffers for
779-
* blocks we aren't deleting, but it's the closest thing in
780-
* bufmgr's API.
781-
*/
782-
FlushRelationBuffers(rel, new_pages);
783-
784-
/*
785-
* Do the physical truncation.
786775
*/
787776
RelationTruncate(rel, new_pages);
788777

‎src/backend/catalog/heap.c‎

Lines changed: 3 additions & 21 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/catalog/heap.c,v 1.280 2005/01/27 03:17:17 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/catalog/heap.c,v 1.281 2005/03/20 22:00:51 tgl Exp $
1212
*
1313
*
1414
* INTERFACE ROUTINES
@@ -1174,12 +1174,6 @@ heap_drop_with_catalog(Oid relid)
11741174
*/
11751175
rel = relation_open(relid, AccessExclusiveLock);
11761176

1177-
/*
1178-
* Release all buffers that belong to this relation, after writing any
1179-
* that are dirty
1180-
*/
1181-
FlushRelationBuffers(rel, (BlockNumber) 0);
1182-
11831177
/*
11841178
* Schedule unlinking of the relation's physical file at commit.
11851179
*/
@@ -1958,13 +1952,7 @@ RelationTruncateIndexes(Oid heapId)
19581952
/* Fetch info needed for index_build */
19591953
indexInfo = BuildIndexInfo(currentIndex);
19601954

1961-
/*
1962-
* Drop any buffers associated with this index. If they're dirty,
1963-
* they're just dropped without bothering to flush to disk.
1964-
*/
1965-
DropRelationBuffers(currentIndex);
1966-
1967-
/* Now truncate the actual data */
1955+
/* Now truncate the actual file (and discard buffers) */
19681956
RelationTruncate(currentIndex, 0);
19691957

19701958
/* Initialize the index and rebuild */
@@ -2024,13 +2012,7 @@ heap_truncate(List *relids)
20242012
{
20252013
Relation rel = lfirst(cell);
20262014

2027-
/*
2028-
* Release any buffers associated with this relation. If they're
2029-
* dirty, they're just dropped without bothering to flush to disk.
2030-
*/
2031-
DropRelationBuffers(rel);
2032-
2033-
/* Now truncate the actual data */
2015+
/* Truncate the actual file (and discard buffers) */
20342016
RelationTruncate(rel, 0);
20352017

20362018
/* If this relation has indexes, truncate the indexes too */

‎src/backend/catalog/index.c‎

Lines changed: 3 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.247 2005/03/16 21:38:04 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.248 2005/03/20 22:00:51 tgl Exp $
1212
*
1313
*
1414
* INTERFACE ROUTINES
@@ -775,10 +775,8 @@ index_drop(Oid indexId)
775775
LockRelation(userIndexRelation, AccessExclusiveLock);
776776

777777
/*
778-
* flush buffer cache and schedule physical removal of the file
778+
* Schedule physical removal of the file
779779
*/
780-
FlushRelationBuffers(userIndexRelation, (BlockNumber) 0);
781-
782780
RelationOpenSmgr(userIndexRelation);
783781
smgrscheduleunlink(userIndexRelation->rd_smgr,
784782
userIndexRelation->rd_istemp);
@@ -1617,14 +1615,7 @@ reindex_index(Oid indexId)
16171615

16181616
if (inplace)
16191617
{
1620-
/*
1621-
* Release any buffers associated with this index. If they're
1622-
* dirty, they're just dropped without bothering to flush to
1623-
* disk.
1624-
*/
1625-
DropRelationBuffers(iRel);
1626-
1627-
/* Now truncate the actual data */
1618+
/* Truncate the actual file (and discard buffers) */
16281619
RelationTruncate(iRel, 0);
16291620
}
16301621
else

‎src/backend/commands/cluster.c‎

Lines changed: 2 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@
1111
*
1212
*
1313
* IDENTIFICATION
14-
* $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.132 2005/02/06 20:19:08 tgl Exp $
14+
* $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.133 2005/03/20 22:00:52 tgl Exp $
1515
*
1616
*-------------------------------------------------------------------------
1717
*/
@@ -709,8 +709,7 @@ copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex)
709709
void
710710
swap_relation_files(Oid r1, Oid r2)
711711
{
712-
Relation relRelation,
713-
rel;
712+
Relation relRelation;
714713
HeapTuple reltup1,
715714
reltup2;
716715
Form_pg_class relform1,
@@ -735,20 +734,6 @@ swap_relation_files(Oid r1, Oid r2)
735734
elog(ERROR, "cache lookup failed for relation %u", r2);
736735
relform2 = (Form_pg_class) GETSTRUCT(reltup2);
737736

738-
/*
739-
* The buffer manager gets confused if we swap relfilenodes for
740-
* relations that are not both local or non-local to this transaction.
741-
* Flush the buffers on both relations so the buffer manager can
742-
* forget about'em. (XXX this might not be necessary anymore?)
743-
*/
744-
rel = relation_open(r1, NoLock);
745-
FlushRelationBuffers(rel, 0);
746-
relation_close(rel, NoLock);
747-
748-
rel = relation_open(r2, NoLock);
749-
FlushRelationBuffers(rel, 0);
750-
relation_close(rel, NoLock);
751-
752737
/*
753738
* Actually swap the fields in the two tuples
754739
*/

‎src/backend/commands/tablecmds.c‎

Lines changed: 5 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.147 2005/03/16 21:38:05 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.148 2005/03/20 22:00:52 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -5628,13 +5628,12 @@ copy_relation_data(Relation rel, SMgrRelation dst)
56285628
Page page = (Page) buf;
56295629

56305630
/*
5631-
* Since we copy the data directly without looking at the shared
5631+
* Since we copy the file directly without looking at the shared
56325632
* buffers, we'd better first flush out any pages of the source
5633-
* relation that are in shared buffers. We assume no new pages will
5634-
* get loaded into buffers while we are holding exclusive lock on the
5635-
* rel.
5633+
* relation that are in shared buffers. We assume no new changes
5634+
* will be made while we are holding exclusive lock on the rel.
56365635
*/
5637-
FlushRelationBuffers(rel, 0);
5636+
FlushRelationBuffers(rel);
56385637

56395638
/*
56405639
* We need to log the copied data in WAL iff WAL archiving is enabled

‎src/backend/commands/vacuum.c‎

Lines changed: 5 additions & 33 deletions
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,7 @@
1313
*
1414
*
1515
* IDENTIFICATION
16-
* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.304 2005/03/16 21:38:05 tgl Exp $
16+
* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.305 2005/03/20 22:00:52 tgl Exp $
1717
*
1818
*-------------------------------------------------------------------------
1919
*/
@@ -1138,16 +1138,6 @@ full_vacuum_rel(Relation onerel, VacuumStmt *vacstmt)
11381138
/* Clean pages from vacuum_pages list */
11391139
vacuum_heap(vacrelstats, onerel, &vacuum_pages);
11401140
}
1141-
else
1142-
{
1143-
/*
1144-
* Flush dirty pages out to disk. We must do this even if we
1145-
* didn't do anything else, because we want to ensure that all
1146-
* tuples have correct on-row commit status on disk (see
1147-
* bufmgr.c's comments for FlushRelationBuffers()).
1148-
*/
1149-
FlushRelationBuffers(onerel, vacrelstats->rel_pages);
1150-
}
11511141
}
11521142

11531143
/* update shared free space map with final free space info */
@@ -2420,15 +2410,7 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
24202410
pfree(Nvacpagelist.pagedesc);
24212411
}
24222412

2423-
/*
2424-
* Flush dirty pages out to disk. We do this unconditionally, even if
2425-
* we don't need to truncate, because we want to ensure that all
2426-
* tuples have correct on-row commit status on disk (see bufmgr.c's
2427-
* comments for FlushRelationBuffers()).
2428-
*/
2429-
FlushRelationBuffers(onerel, blkno);
2430-
2431-
/* truncate relation, if needed */
2413+
/* Truncate relation, if needed */
24322414
if (blkno < nblocks)
24332415
{
24342416
RelationTruncate(onerel, blkno);
@@ -2818,27 +2800,17 @@ vacuum_heap(VRelStats *vacrelstats, Relation onerel, VacPageList vacuum_pages)
28182800
}
28192801
}
28202802

2821-
/*
2822-
* Flush dirty pages out to disk. We do this unconditionally, even if
2823-
* we don't need to truncate, because we want to ensure that all
2824-
* tuples have correct on-row commit status on disk (see bufmgr.c's
2825-
* comments for FlushRelationBuffers()).
2826-
*/
2803+
/* Truncate relation if there are some empty end-pages */
28272804
Assert(vacrelstats->rel_pages >= vacuum_pages->empty_end_pages);
2828-
relblocks = vacrelstats->rel_pages - vacuum_pages->empty_end_pages;
2829-
2830-
FlushRelationBuffers(onerel, relblocks);
2831-
2832-
/* truncate relation if there are some empty end-pages */
28332805
if (vacuum_pages->empty_end_pages > 0)
28342806
{
2807+
relblocks = vacrelstats->rel_pages - vacuum_pages->empty_end_pages;
28352808
ereport(elevel,
28362809
(errmsg("\"%s\": truncated %u to %u pages",
28372810
RelationGetRelationName(onerel),
28382811
vacrelstats->rel_pages, relblocks)));
28392812
RelationTruncate(onerel, relblocks);
2840-
vacrelstats->rel_pages = relblocks; /* set new number of
2841-
* blocks */
2813+
vacrelstats->rel_pages = relblocks; /* set new number of blocks */
28422814
}
28432815
}
28442816

‎src/backend/commands/vacuumlazy.c‎

Lines changed: 1 addition & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -31,7 +31,7 @@
3131
*
3232
*
3333
* IDENTIFICATION
34-
* $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.50 2004/12/31 21:59:42 pgsql Exp $
34+
* $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.51 2005/03/20 22:00:52 tgl Exp $
3535
*
3636
*-------------------------------------------------------------------------
3737
*/
@@ -773,16 +773,6 @@ lazy_truncate_heap(Relation onerel, LVRelStats *vacrelstats)
773773

774774
/*
775775
* Okay to truncate.
776-
*
777-
* First, flush any shared buffers for the blocks we intend to delete.
778-
* FlushRelationBuffers is a bit more than we need for this, since it
779-
* will also write out dirty buffers for blocks we aren't deleting,
780-
* but it's the closest thing in bufmgr's API.
781-
*/
782-
FlushRelationBuffers(onerel, new_rel_pages);
783-
784-
/*
785-
* Do the physical truncation.
786776
*/
787777
RelationTruncate(onerel, new_rel_pages);
788778

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