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Speedup truncations of relation forks.

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When a relation is truncated, shared_buffers needs to be scanned
so that any buffers for the relation forks are invalidated in it.
Previously, shared_buffers was scanned for each relation forks, i.e.,
MAIN, FSM and VM, when VACUUM truncated off any empty pages
at the end of relation or TRUNCATE truncated the relation in place.
Since shared_buffers needed to be scanned multiple times,
it could take a long time to finish those commands especially
when shared_buffers was large.

This commit changes the logic so that shared_buffers is scanned only
one time for those three relation forks.

Author: Kirk Jamison
Reviewed-by: Masahiko Sawada, Thomas Munro, Alvaro Herrera, Takayuki Tsunakawa and Fujii Masao
Discussion: https://postgr.es/m/D09B13F772D2274BB348A310EE3027C64E2067@g01jpexmbkw24
This commit is contained in:
Fujii Masao
2019-09-24 17:31:26 +09:00
parent 2e5c83acbb
commit 6d05086c0a
10 changed files with 172 additions and 86 deletions
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87
src/backend/catalog/storage.c
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@@ -231,6 +231,10 @@ RelationTruncate(Relation rel, BlockNumber nblocks)
{
bool fsm;
bool vm;
bool need_fsm_vacuum = false;
ForkNumber forks[MAX_FORKNUM];
BlockNumber blocks[MAX_FORKNUM];
int nforks = 0;
/* Open it at the smgr level if not already done */
RelationOpenSmgr(rel);
@@ -242,15 +246,35 @@ RelationTruncate(Relation rel, BlockNumber nblocks)
rel->rd_smgr->smgr_fsm_nblocks = InvalidBlockNumber;
rel->rd_smgr->smgr_vm_nblocks = InvalidBlockNumber;
/* Truncate the FSM first if it exists */
/* Prepare for truncation of MAIN fork of the relation */
forks[nforks] = MAIN_FORKNUM;
blocks[nforks] = nblocks;
nforks++;
/* Prepare for truncation of the FSM if it exists */
fsm = smgrexists(rel->rd_smgr, FSM_FORKNUM);
if (fsm)
FreeSpaceMapTruncateRel(rel, nblocks);
{
blocks[nforks] = FreeSpaceMapPrepareTruncateRel(rel, nblocks);
if (BlockNumberIsValid(blocks[nforks]))
{
forks[nforks] = FSM_FORKNUM;
nforks++;
need_fsm_vacuum = true;
}
}
/* Truncate the visibility map too if it exists. */
/* Prepare for truncation of the visibility map too if it exists */
vm = smgrexists(rel->rd_smgr, VISIBILITYMAP_FORKNUM);
if (vm)
visibilitymap_truncate(rel, nblocks);
{
blocks[nforks] = visibilitymap_prepare_truncate(rel, nblocks);
if (BlockNumberIsValid(blocks[nforks]))
{
forks[nforks] = VISIBILITYMAP_FORKNUM;
nforks++;
}
}
/*
* We WAL-log the truncation before actually truncating, which means
@@ -290,8 +314,16 @@ RelationTruncate(Relation rel, BlockNumber nblocks)
XLogFlush(lsn);
}
/* Do the real work */
smgrtruncate(rel->rd_smgr, MAIN_FORKNUM, nblocks);
/* Do the real work to truncate relation forks */
smgrtruncate(rel->rd_smgr, forks, nforks, blocks);
/*
* Update upper-level FSM pages to account for the truncation.
* This is important because the just-truncated pages were likely
* marked as all-free, and would be preferentially selected.
*/
if (need_fsm_vacuum)
FreeSpaceMapVacuumRange(rel, nblocks, InvalidBlockNumber);
}
/*
@@ -588,6 +620,10 @@ smgr_redo(XLogReaderState *record)
xl_smgr_truncate *xlrec = (xl_smgr_truncate *) XLogRecGetData(record);
SMgrRelation reln;
Relation rel;
ForkNumber forks[MAX_FORKNUM];
BlockNumber blocks[MAX_FORKNUM];
int nforks = 0;
bool need_fsm_vacuum = false;
reln = smgropen(xlrec->rnode, InvalidBackendId);
@@ -616,23 +652,54 @@ smgr_redo(XLogReaderState *record)
*/
XLogFlush(lsn);
/* Prepare for truncation of MAIN fork */
if ((xlrec->flags & SMGR_TRUNCATE_HEAP) != 0)
{
smgrtruncate(reln, MAIN_FORKNUM, xlrec->blkno);
forks[nforks] = MAIN_FORKNUM;
blocks[nforks] = xlrec->blkno;
nforks++;
/* Also tell xlogutils.c about it */
XLogTruncateRelation(xlrec->rnode, MAIN_FORKNUM, xlrec->blkno);
}
/* Truncate FSM and VM too */
/* Prepare for truncation of FSM and VM too */
rel = CreateFakeRelcacheEntry(xlrec->rnode);
if ((xlrec->flags & SMGR_TRUNCATE_FSM) != 0 &&
smgrexists(reln, FSM_FORKNUM))
FreeSpaceMapTruncateRel(rel, xlrec->blkno);
{
blocks[nforks] = FreeSpaceMapPrepareTruncateRel(rel, xlrec->blkno);
if (BlockNumberIsValid(blocks[nforks]))
{
forks[nforks] = FSM_FORKNUM;
nforks++;
need_fsm_vacuum = true;
}
}
if ((xlrec->flags & SMGR_TRUNCATE_VM) != 0 &&
smgrexists(reln, VISIBILITYMAP_FORKNUM))
visibilitymap_truncate(rel, xlrec->blkno);
{
blocks[nforks] = visibilitymap_prepare_truncate(rel, xlrec->blkno);
if (BlockNumberIsValid(blocks[nforks]))
{
forks[nforks] = VISIBILITYMAP_FORKNUM;
nforks++;
}
}
/* Do the real work to truncate relation forks */
if (nforks > 0)
smgrtruncate(reln, forks, nforks, blocks);
/*
* Update upper-level FSM pages to account for the truncation.
* This is important because the just-truncated pages were likely
* marked as all-free, and would be preferentially selected.
*/
if (need_fsm_vacuum)
FreeSpaceMapVacuumRange(rel, xlrec->blkno,
InvalidBlockNumber);
FreeFakeRelcacheEntry(rel);
}