CREATE EXTENSION pg_visibility;
+CREATE EXTENSION pageinspect;
--
-- recently-dropped table
--
(1 row)
+-- test the case where vacuum phase I does not need to modify the heap buffer
+-- and only needs to set the VM
+create table test_vac_unmodified_heap(a int);
+insert into test_vac_unmodified_heap values (1);
+vacuum (freeze) test_vac_unmodified_heap;
+select pg_visibility_map_summary('test_vac_unmodified_heap');
+ pg_visibility_map_summary
+---------------------------
+ (1,1)
+(1 row)
+
+-- the checkpoint cleans the buffer dirtied by freezing the sole tuple
+checkpoint;
+-- truncating the VM ensures that the next vacuum will need to set it
+select pg_truncate_visibility_map('test_vac_unmodified_heap');
+ pg_truncate_visibility_map
+----------------------------
+
+(1 row)
+
+select pg_visibility_map_summary('test_vac_unmodified_heap');
+ pg_visibility_map_summary
+---------------------------
+ (0,0)
+(1 row)
+
+-- though the VM is truncated, the heap page-level visibility hint,
+-- PD_ALL_VISIBLE should still be set
+SELECT (flags & x'0004'::int) <> 0
+ FROM page_header(get_raw_page('test_vac_unmodified_heap', 0));
+ ?column?
+----------
+ t
+(1 row)
+
+-- vacuum sets the VM
+vacuum test_vac_unmodified_heap;
+select pg_visibility_map_summary('test_vac_unmodified_heap');
+ pg_visibility_map_summary
+---------------------------
+ (1,1)
+(1 row)
+
-- test copy freeze
create table copyfreeze (a int, b char(1500));
-- load all rows via COPY FREEZE and ensure that all pages are set all-visible
CREATE EXTENSION pg_visibility;
+CREATE EXTENSION pageinspect;
--
-- recently-dropped table
select * from pg_check_frozen('test_partition'); -- hopefully none
select pg_truncate_visibility_map('test_partition');
+-- test the case where vacuum phase I does not need to modify the heap buffer
+-- and only needs to set the VM
+create table test_vac_unmodified_heap(a int);
+insert into test_vac_unmodified_heap values (1);
+vacuum (freeze) test_vac_unmodified_heap;
+select pg_visibility_map_summary('test_vac_unmodified_heap');
+-- the checkpoint cleans the buffer dirtied by freezing the sole tuple
+checkpoint;
+-- truncating the VM ensures that the next vacuum will need to set it
+select pg_truncate_visibility_map('test_vac_unmodified_heap');
+select pg_visibility_map_summary('test_vac_unmodified_heap');
+-- though the VM is truncated, the heap page-level visibility hint,
+-- PD_ALL_VISIBLE should still be set
+SELECT (flags & x'0004'::int) <> 0
+ FROM page_header(get_raw_page('test_vac_unmodified_heap', 0));
+-- vacuum sets the VM
+vacuum test_vac_unmodified_heap;
+select pg_visibility_map_summary('test_vac_unmodified_heap');
+
-- test copy freeze
create table copyfreeze (a int, b char(1500));
* of last heap_vac_scan_next_block() call), and from all_visible and
* all_frozen variables
*/
- if (!all_visible_according_to_vm && presult.all_visible)
+ if ((presult.all_visible && !all_visible_according_to_vm) ||
+ (presult.all_frozen && !VM_ALL_FROZEN(rel, blkno, &vmbuffer)))
{
uint8 old_vmbits;
uint8 flags = VISIBILITYMAP_ALL_VISIBLE;
if (presult.all_frozen)
- {
- Assert(!TransactionIdIsValid(presult.vm_conflict_horizon));
flags |= VISIBILITYMAP_ALL_FROZEN;
- }
/*
* It should never be the case that the visibility map page is set
* checksums are not enabled). Regardless, set 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.
+ * Even if PD_ALL_VISIBLE is already set, we don't need to worry about
+ * unnecessarily dirtying the heap buffer. Nearly the only scenario
+ * where PD_ALL_VISIBLE is set but the VM is not is if the VM was
+ * removed -- and that isn't worth optimizing for. And if we add the
+ * heap buffer to the WAL chain (without passing REGBUF_NO_CHANGES),
+ * it must be marked dirty.
*/
PageSetAllVisible(page);
MarkBufferDirty(buf);
+
+ /*
+ * If the page is being set all-frozen, we pass InvalidTransactionId
+ * as the cutoff_xid, since a snapshot conflict horizon sufficient to
+ * make everything safe for REDO was logged when the page's tuples
+ * were frozen.
+ */
+ Assert(!presult.all_frozen ||
+ !TransactionIdIsValid(presult.vm_conflict_horizon));
+
old_vmbits = visibilitymap_set(vacrel->rel, blkno, buf,
InvalidXLogRecPtr,
vmbuffer, presult.vm_conflict_horizon,
VISIBILITYMAP_VALID_BITS);
}
- /*
- * If the all-visible page is all-frozen but not marked as such yet, mark
- * it as all-frozen.
- */
- else if (all_visible_according_to_vm && presult.all_frozen &&
- !VM_ALL_FROZEN(vacrel->rel, blkno, &vmbuffer))
- {
- uint8 old_vmbits;
-
- /*
- * Avoid relying on all_visible_according_to_vm as a proxy for the
- * page-level PD_ALL_VISIBLE bit being set, since it might have become
- * stale -- even when all_visible is set
- */
- if (!PageIsAllVisible(page))
- {
- PageSetAllVisible(page);
- MarkBufferDirty(buf);
- }
-
- /*
- * Set the page all-frozen (and all-visible) in the VM.
- *
- * We can pass InvalidTransactionId as our cutoff_xid, since a
- * snapshotConflictHorizon sufficient to make everything safe for REDO
- * was logged when the page's tuples were frozen.
- */
- Assert(!TransactionIdIsValid(presult.vm_conflict_horizon));
- old_vmbits = visibilitymap_set(vacrel->rel, blkno, buf,
- InvalidXLogRecPtr,
- vmbuffer, InvalidTransactionId,
- VISIBILITYMAP_ALL_VISIBLE |
- VISIBILITYMAP_ALL_FROZEN);
-
- /*
- * The page was likely already set all-visible in the VM. However,
- * there is a small chance that it was modified sometime between
- * setting all_visible_according_to_vm and checking the visibility
- * during pruning. Check the return value of old_vmbits anyway to
- * ensure the visibility map counters used for logging are accurate.
- */
- if ((old_vmbits & VISIBILITYMAP_ALL_VISIBLE) == 0)
- {
- vacrel->vm_new_visible_pages++;
- vacrel->vm_new_visible_frozen_pages++;
- *vm_page_frozen = true;
- }
-
- /*
- * We already checked that the page was not set all-frozen in the VM
- * above, so we don't need to test the value of old_vmbits.
- */
- else
- {
- vacrel->vm_new_frozen_pages++;
- *vm_page_frozen = true;
- }
- }
-
return presult.ndeleted;
}
projects / thirdparty / postgresql.git / commitdiff
