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Ensure we MarkBufferDirty before visibilitymap_set() 

logs the heap page and sets the LSN. Otherwise a
checkpoint could occur between those actions and
leave us in an inconsistent state.

Jeff Davis
This commit is contained in:
Simon Riggs 2013-04-30 08:15:49 +01:00
parent fdea2530bd
commit 730924397c
1 changed files with 26 additions and 21 deletions
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47
src/backend/commands/vacuumlazy.c
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@ -894,26 +894,25 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
freespace = PageGetHeapFreeSpace(page);
/* mark page all-visible, if appropriate */
if (all_visible)
if (all_visible && !all_visible_according_to_vm)
{
if (!PageIsAllVisible(page))
{
PageSetAllVisible(page);
MarkBufferDirty(buf);
visibilitymap_set(onerel, blkno, buf, InvalidXLogRecPtr,
vmbuffer, visibility_cutoff_xid);
}
else if (!all_visible_according_to_vm)
{
/*
* It should never be the case that the visibility map page is
* set while the page-level bit is clear, but the reverse is
* allowed. Set the visibility map bit as well so that we get
* back in sync.
*/
visibilitymap_set(onerel, blkno, buf, InvalidXLogRecPtr,
vmbuffer, visibility_cutoff_xid);
}
/*
* It should never be the case that the visibility map page is set
* while the page-level bit is clear, but the reverse is allowed
* (if checksums are not enabled). Regardless, set the both bits
* so that we get back in sync.
*
* NB: If the heap page is all-visible but the VM bit is not set,
* we don't need to dirty the heap page. However, if checksums are
* enabled, we do need to make sure that the heap page is dirtied
* before passing it to visibilitymap_set(), because it may be
* logged. Given that this situation should only happen in rare
* cases after a crash, it is not worth optimizing.
*/
PageSetAllVisible(page);
MarkBufferDirty(buf);
visibilitymap_set(onerel, blkno, buf, InvalidXLogRecPtr,
vmbuffer, visibility_cutoff_xid);
}
/*
@ -1138,6 +1137,14 @@ lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
PageRepairFragmentation(page);
/*
* Mark buffer dirty before we write WAL.
*
* If checksums are enabled, visibilitymap_set() may log the heap page, so
* we must mark heap buffer dirty before calling visibilitymap_set().
*/
MarkBufferDirty(buffer);
/*
* Now that we have removed the dead tuples from the page, once again check
* if the page has become all-visible.
@ -1151,8 +1158,6 @@ lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
visibility_cutoff_xid);
}
MarkBufferDirty(buffer);
/* XLOG stuff */
if (RelationNeedsWAL(onerel))
{