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Move VM update code from lazy_scan_heap() to lazy_scan_prune().
Most of the output parameters of lazy_scan_prune() were being used to update the VM in lazy_scan_heap(). Moving that code into lazy_scan_prune() simplifies lazy_scan_heap() and requires less communication between the two. This change permits some further code simplification, but that is left for a separate commit. Melanie Plageman, reviewed by me. Discussion: http://postgr.es/m/CAAKRu_aM=OL85AOr-80wBsCr=vLVzhnaavqkVPRkFBtD0zsuLQ@mail.gmail.com
This commit is contained in:
Robert Haas
parent
0a157a4d44
commit
cb970240f1
@ -249,6 +249,7 @@ static bool lazy_scan_new_or_empty(LVRelState *vacrel, Buffer buf,
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bool sharelock, Buffer vmbuffer);
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static void lazy_scan_prune(LVRelState *vacrel, Buffer buf,
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BlockNumber blkno, Page page,
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Buffer vmbuffer, bool all_visible_according_to_vm,
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LVPagePruneState *prunestate);
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static bool lazy_scan_noprune(LVRelState *vacrel, Buffer buf,
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BlockNumber blkno, Page page,
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@ -1032,117 +1033,9 @@ lazy_scan_heap(LVRelState *vacrel)
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* tuple headers of remaining items with storage. It also determines
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* if truncating this block is safe.
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*/
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lazy_scan_prune(vacrel, buf, blkno, page, &prunestate);
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Assert(!prunestate.all_visible || !prunestate.has_lpdead_items);
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/*
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* Handle setting visibility map bit based on information from the VM
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* (as of last lazy_scan_skip() call), and from prunestate
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*/
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if (!all_visible_according_to_vm && prunestate.all_visible)
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{
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uint8 flags = VISIBILITYMAP_ALL_VISIBLE;
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if (prunestate.all_frozen)
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{
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Assert(!TransactionIdIsValid(prunestate.visibility_cutoff_xid));
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flags |= VISIBILITYMAP_ALL_FROZEN;
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}
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/*
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* It should never be the case that the visibility map page is set
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* while the page-level bit is clear, but the reverse is allowed
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* (if checksums are not enabled). Regardless, set both bits so
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* that we get back in sync.
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*
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* NB: If the heap page is all-visible but the VM bit is not set,
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* we don't need to dirty the heap page. However, if checksums
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* are enabled, we do need to make sure that the heap page is
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* dirtied before passing it to visibilitymap_set(), because it
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* may be logged. Given that this situation should only happen in
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* rare cases after a crash, it is not worth optimizing.
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*/
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PageSetAllVisible(page);
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MarkBufferDirty(buf);
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visibilitymap_set(vacrel->rel, blkno, buf, InvalidXLogRecPtr,
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vmbuffer, prunestate.visibility_cutoff_xid,
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flags);
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}
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/*
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* As of PostgreSQL 9.2, the visibility map bit should never be set if
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* the page-level bit is clear. However, it's possible that the bit
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* got cleared after lazy_scan_skip() was called, so we must recheck
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* with buffer lock before concluding that the VM is corrupt.
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*/
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else if (all_visible_according_to_vm && !PageIsAllVisible(page) &&
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visibilitymap_get_status(vacrel->rel, blkno, &vmbuffer) != 0)
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{
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elog(WARNING, "page is not marked all-visible but visibility map bit is set in relation \"%s\" page %u",
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vacrel->relname, blkno);
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visibilitymap_clear(vacrel->rel, blkno, vmbuffer,
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VISIBILITYMAP_VALID_BITS);
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}
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/*
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* It's possible for the value returned by
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* GetOldestNonRemovableTransactionId() to move backwards, so it's not
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* wrong for us to see tuples that appear to not be visible to
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* everyone yet, while PD_ALL_VISIBLE is already set. The real safe
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* xmin value never moves backwards, but
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* GetOldestNonRemovableTransactionId() is conservative and sometimes
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* returns a value that's unnecessarily small, so if we see that
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* contradiction it just means that the tuples that we think are not
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* visible to everyone yet actually are, and the PD_ALL_VISIBLE flag
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* is correct.
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*
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* There should never be LP_DEAD items on a page with PD_ALL_VISIBLE
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* set, however.
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*/
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else if (prunestate.has_lpdead_items && PageIsAllVisible(page))
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{
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elog(WARNING, "page containing LP_DEAD items is marked as all-visible in relation \"%s\" page %u",
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vacrel->relname, blkno);
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PageClearAllVisible(page);
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MarkBufferDirty(buf);
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visibilitymap_clear(vacrel->rel, blkno, vmbuffer,
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VISIBILITYMAP_VALID_BITS);
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}
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/*
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* If the all-visible page is all-frozen but not marked as such yet,
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* mark it as all-frozen. Note that all_frozen is only valid if
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* all_visible is true, so we must check both prunestate fields.
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*/
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else if (all_visible_according_to_vm && prunestate.all_visible &&
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prunestate.all_frozen &&
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!VM_ALL_FROZEN(vacrel->rel, blkno, &vmbuffer))
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{
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/*
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* Avoid relying on all_visible_according_to_vm as a proxy for the
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* page-level PD_ALL_VISIBLE bit being set, since it might have
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* become stale -- even when all_visible is set in prunestate
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*/
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if (!PageIsAllVisible(page))
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{
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PageSetAllVisible(page);
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MarkBufferDirty(buf);
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}
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/*
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* Set the page all-frozen (and all-visible) in the VM.
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*
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* We can pass InvalidTransactionId as our visibility_cutoff_xid,
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* since a snapshotConflictHorizon sufficient to make everything
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* safe for REDO was logged when the page's tuples were frozen.
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*/
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Assert(!TransactionIdIsValid(prunestate.visibility_cutoff_xid));
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visibilitymap_set(vacrel->rel, blkno, buf, InvalidXLogRecPtr,
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vmbuffer, InvalidTransactionId,
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VISIBILITYMAP_ALL_VISIBLE |
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VISIBILITYMAP_ALL_FROZEN);
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}
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lazy_scan_prune(vacrel, buf, blkno, page,
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vmbuffer, all_visible_according_to_vm,
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&prunestate);
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/*
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* Final steps for block: drop cleanup lock, record free space in the
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@ -1496,6 +1389,8 @@ lazy_scan_prune(LVRelState *vacrel,
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Buffer buf,
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BlockNumber blkno,
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Page page,
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Buffer vmbuffer,
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bool all_visible_according_to_vm,
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LVPagePruneState *prunestate)
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{
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Relation rel = vacrel->rel;
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@ -1880,6 +1775,115 @@ lazy_scan_prune(LVRelState *vacrel,
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/* Can't truncate this page */
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if (hastup)
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vacrel->nonempty_pages = blkno + 1;
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Assert(!prunestate->all_visible || !prunestate->has_lpdead_items);
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/*
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* Handle setting visibility map bit based on information from the VM (as
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* of last lazy_scan_skip() call), and from prunestate
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*/
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if (!all_visible_according_to_vm && prunestate->all_visible)
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{
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uint8 flags = VISIBILITYMAP_ALL_VISIBLE;
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if (prunestate->all_frozen)
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{
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Assert(!TransactionIdIsValid(prunestate->visibility_cutoff_xid));
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flags |= VISIBILITYMAP_ALL_FROZEN;
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}
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/*
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* It should never be the case that the visibility map page is set
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* while the page-level bit is clear, but the reverse is allowed (if
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* checksums are not enabled). Regardless, set both bits so that we
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* get back in sync.
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*
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* NB: If the heap page is all-visible but the VM bit is not set, we
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* don't need to dirty the heap page. However, if checksums are
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* enabled, we do need to make sure that the heap page is dirtied
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* before passing it to visibilitymap_set(), because it may be logged.
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* Given that this situation should only happen in rare cases after a
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* crash, it is not worth optimizing.
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*/
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PageSetAllVisible(page);
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MarkBufferDirty(buf);
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visibilitymap_set(vacrel->rel, blkno, buf, InvalidXLogRecPtr,
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vmbuffer, prunestate->visibility_cutoff_xid,
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flags);
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}
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/*
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* As of PostgreSQL 9.2, the visibility map bit should never be set if the
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* page-level bit is clear. However, it's possible that the bit got
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* cleared after lazy_scan_skip() was called, so we must recheck with
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* buffer lock before concluding that the VM is corrupt.
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*/
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else if (all_visible_according_to_vm && !PageIsAllVisible(page) &&
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visibilitymap_get_status(vacrel->rel, blkno, &vmbuffer) != 0)
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{
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elog(WARNING, "page is not marked all-visible but visibility map bit is set in relation \"%s\" page %u",
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vacrel->relname, blkno);
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visibilitymap_clear(vacrel->rel, blkno, vmbuffer,
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VISIBILITYMAP_VALID_BITS);
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}
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/*
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* It's possible for the value returned by
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* GetOldestNonRemovableTransactionId() to move backwards, so it's not
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* wrong for us to see tuples that appear to not be visible to everyone
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* yet, while PD_ALL_VISIBLE is already set. The real safe xmin value
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* never moves backwards, but GetOldestNonRemovableTransactionId() is
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* conservative and sometimes returns a value that's unnecessarily small,
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* so if we see that contradiction it just means that the tuples that we
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* think are not visible to everyone yet actually are, and the
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* PD_ALL_VISIBLE flag is correct.
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*
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* There should never be LP_DEAD items on a page with PD_ALL_VISIBLE set,
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* however.
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*/
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else if (prunestate->has_lpdead_items && PageIsAllVisible(page))
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{
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elog(WARNING, "page containing LP_DEAD items is marked as all-visible in relation \"%s\" page %u",
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vacrel->relname, blkno);
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PageClearAllVisible(page);
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MarkBufferDirty(buf);
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visibilitymap_clear(vacrel->rel, blkno, vmbuffer,
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VISIBILITYMAP_VALID_BITS);
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}
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/*
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* If the all-visible page is all-frozen but not marked as such yet, mark
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* it as all-frozen. Note that all_frozen is only valid if all_visible is
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* true, so we must check both prunestate fields.
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*/
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else if (all_visible_according_to_vm && prunestate->all_visible &&
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prunestate->all_frozen &&
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!VM_ALL_FROZEN(vacrel->rel, blkno, &vmbuffer))
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{
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/*
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* Avoid relying on all_visible_according_to_vm as a proxy for the
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* page-level PD_ALL_VISIBLE bit being set, since it might have become
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* stale -- even when all_visible is set in prunestate
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*/
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if (!PageIsAllVisible(page))
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{
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PageSetAllVisible(page);
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MarkBufferDirty(buf);
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}
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/*
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* Set the page all-frozen (and all-visible) in the VM.
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*
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* We can pass InvalidTransactionId as our visibility_cutoff_xid,
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* since a snapshotConflictHorizon sufficient to make everything safe
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* for REDO was logged when the page's tuples were frozen.
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*/
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Assert(!TransactionIdIsValid(prunestate->visibility_cutoff_xid));
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visibilitymap_set(vacrel->rel, blkno, buf, InvalidXLogRecPtr,
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vmbuffer, InvalidTransactionId,
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VISIBILITYMAP_ALL_VISIBLE |
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VISIBILITYMAP_ALL_FROZEN);
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}
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}
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/*
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