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Cache smgrnblocks() results in recovery.

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Avoid repeatedly calling lseek(SEEK_END) during recovery by caching
the size of each fork.  For now, we can't use the same technique in
other processes, because we lack a shared invalidation mechanism.

Do this by generalizing the pre-existing caching used by FSM and VM
to support all forks.

Discussion: https://postgr.es/m/CAEepm%3D3SSw-Ty1DFcK%3D1rU-K6GSzYzfdD4d%2BZwapdN7dTa6%3DnQ%40mail.gmail.com
This commit is contained in:
Thomas Munro
2020-07-31 14:15:18 +12:00
parent e3931d01f3
commit c5315f4f44
6 changed files with 66 additions and 46 deletions
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18
src/backend/access/heap/visibilitymap.c
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@@ -561,17 +561,16 @@ vm_readbuf(Relation rel, BlockNumber blkno, bool extend)
* If we haven't cached the size of the visibility map fork yet, check it
* first.
*/
if (rel->rd_smgr->smgr_vm_nblocks == InvalidBlockNumber)
if (rel->rd_smgr->smgr_cached_nblocks[VISIBILITYMAP_FORKNUM] == InvalidBlockNumber)
{
if (smgrexists(rel->rd_smgr, VISIBILITYMAP_FORKNUM))
rel->rd_smgr->smgr_vm_nblocks = smgrnblocks(rel->rd_smgr,
VISIBILITYMAP_FORKNUM);
smgrnblocks(rel->rd_smgr, VISIBILITYMAP_FORKNUM);
else
rel->rd_smgr->smgr_vm_nblocks = 0;
rel->rd_smgr->smgr_cached_nblocks[VISIBILITYMAP_FORKNUM] = 0;
}
/* Handle requests beyond EOF */
if (blkno >= rel->rd_smgr->smgr_vm_nblocks)
if (blkno >= rel->rd_smgr->smgr_cached_nblocks[VISIBILITYMAP_FORKNUM])
{
if (extend)
vm_extend(rel, blkno + 1);
@@ -641,11 +640,13 @@ vm_extend(Relation rel, BlockNumber vm_nblocks)
* Create the file first if it doesn't exist. If smgr_vm_nblocks is
* positive then it must exist, no need for an smgrexists call.
*/
if ((rel->rd_smgr->smgr_vm_nblocks == 0 ||
rel->rd_smgr->smgr_vm_nblocks == InvalidBlockNumber) &&
if ((rel->rd_smgr->smgr_cached_nblocks[VISIBILITYMAP_FORKNUM] == 0 ||
rel->rd_smgr->smgr_cached_nblocks[VISIBILITYMAP_FORKNUM] == InvalidBlockNumber) &&
!smgrexists(rel->rd_smgr, VISIBILITYMAP_FORKNUM))
smgrcreate(rel->rd_smgr, VISIBILITYMAP_FORKNUM, false);
/* Invalidate cache so that smgrnblocks() asks the kernel. */
rel->rd_smgr->smgr_cached_nblocks[VISIBILITYMAP_FORKNUM] = InvalidBlockNumber;
vm_nblocks_now = smgrnblocks(rel->rd_smgr, VISIBILITYMAP_FORKNUM);
/* Now extend the file */
@@ -667,8 +668,5 @@ vm_extend(Relation rel, BlockNumber vm_nblocks)
*/
CacheInvalidateSmgr(rel->rd_smgr->smgr_rnode);
/* Update local cache with the up-to-date size */
rel->rd_smgr->smgr_vm_nblocks = vm_nblocks_now;
UnlockRelationForExtension(rel, ExclusiveLock);
}