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Try again to make the visibility map crash safe.

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My previous attempt was quite a bit less than half-baked with respect to
heap_update().
This commit is contained in:
Robert Haas 2011-06-27 13:55:55 -04:00
parent 66a36ef949
commit e16954f3d2
3 changed files with 100 additions and 44 deletions
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45
src/backend/access/heap/heapam.c
View File

@ -1941,7 +1941,7 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
*/
buffer = RelationGetBufferForTuple(relation, heaptup->t_len,
InvalidBuffer, options, bistate,
&vmbuffer);
&vmbuffer, NULL);
/*
* We're about to do the actual insert -- check for conflict at the
@ -2519,19 +2519,6 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
/*
* If we didn't pin the visibility map page and the page has become all
* visible while we were busy locking the buffer, we'll have to unlock and
* re-lock, to avoid holding the buffer lock across an I/O. That's a bit
* unfortunate, but hopefully shouldn't happen often.
*/
if (vmbuffer == InvalidBuffer && PageIsAllVisible(page))
{
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
visibilitymap_pin(relation, block, &vmbuffer);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
}
lp = PageGetItemId(page, ItemPointerGetOffsetNumber(otid));
Assert(ItemIdIsNormal(lp));
@ -2667,6 +2654,20 @@ l2:
return result;
}
/*
* If we didn't pin the visibility map page and the page has become all
* visible while we were busy locking the buffer, or during some subsequent
* window during which we had it unlocked, we'll have to unlock and
* re-lock, to avoid holding the buffer lock across an I/O. That's a bit
* unfortunate, but hopefully shouldn't happen often.
*/
if (vmbuffer == InvalidBuffer && PageIsAllVisible(page))
{
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
visibilitymap_pin(relation, block, &vmbuffer);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
}
/*
* We're about to do the actual update -- check for conflict first, to
* avoid possibly having to roll back work we've just done.
@ -2784,7 +2785,7 @@ l2:
/* Assume there's no chance to put heaptup on same page. */
newbuf = RelationGetBufferForTuple(relation, heaptup->t_len,
buffer, 0, NULL,
&vmbuffer_new);
&vmbuffer_new, &vmbuffer);
}
else
{
@ -2802,7 +2803,7 @@ l2:
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
newbuf = RelationGetBufferForTuple(relation, heaptup->t_len,
buffer, 0, NULL,
&vmbuffer_new);
&vmbuffer_new, &vmbuffer);
}
else
{
@ -2908,11 +2909,15 @@ l2:
{
all_visible_cleared = true;
PageClearAllVisible(BufferGetPage(buffer));
visibilitymap_clear(relation, BufferGetBlockNumber(buffer),
vmbuffer);
}
if (newbuf != buffer && PageIsAllVisible(BufferGetPage(newbuf)))
{
all_visible_cleared_new = true;
PageClearAllVisible(BufferGetPage(newbuf));
visibilitymap_clear(relation, BufferGetBlockNumber(newbuf),
vmbuffer_new);
}
if (newbuf != buffer)
@ -2949,14 +2954,6 @@ l2:
*/
CacheInvalidateHeapTuple(relation, &oldtup);
/* Clear bits in visibility map */
if (all_visible_cleared)
visibilitymap_clear(relation, BufferGetBlockNumber(buffer),
vmbuffer);
if (all_visible_cleared_new)
visibilitymap_clear(relation, BufferGetBlockNumber(newbuf),
vmbuffer_new);
/* Now we can release the buffer(s) */
if (newbuf != buffer)
ReleaseBuffer(newbuf);

97
src/backend/access/heap/hio.c
View File

@ -96,6 +96,64 @@ ReadBufferBI(Relation relation, BlockNumber targetBlock,
return buffer;
}
/*
* For each heap page which is all-visible, acquire a pin on the appropriate
* visibility map page, if we haven't already got one.
*
* buffer2 may be InvalidBuffer, if only one buffer is involved. buffer1
* must not be InvalidBuffer. If both buffers are specified, buffer1 must
* be less than buffer2.
*/
static void
GetVisibilityMapPins(Relation relation, Buffer buffer1, Buffer buffer2,
BlockNumber block1, BlockNumber block2,
Buffer *vmbuffer1, Buffer *vmbuffer2)
{
bool need_to_pin_buffer1;
bool need_to_pin_buffer2;
Assert(BufferIsValid(buffer1));
Assert(buffer2 == InvalidBuffer || buffer1 <= buffer2);
while (1)
{
/* Figure out which pins we need but don't have. */
need_to_pin_buffer1 = PageIsAllVisible(BufferGetPage(buffer1))
&& !visibilitymap_pin_ok(block1, *vmbuffer1);
need_to_pin_buffer2 = buffer2 != InvalidBuffer
&& PageIsAllVisible(BufferGetPage(buffer2))
&& !visibilitymap_pin_ok(block2, *vmbuffer2);
if (!need_to_pin_buffer1 && !need_to_pin_buffer2)
return;
/* We must unlock both buffers before doing any I/O. */
LockBuffer(buffer1, BUFFER_LOCK_UNLOCK);
if (buffer2 != InvalidBuffer && buffer2 != buffer1)
LockBuffer(buffer2, BUFFER_LOCK_UNLOCK);
/* Get pins. */
if (need_to_pin_buffer1)
visibilitymap_pin(relation, block1, vmbuffer1);
if (need_to_pin_buffer2)
visibilitymap_pin(relation, block2, vmbuffer2);
/* Relock buffers. */
LockBuffer(buffer1, BUFFER_LOCK_EXCLUSIVE);
if (buffer2 != InvalidBuffer && buffer2 != buffer1)
LockBuffer(buffer2, BUFFER_LOCK_EXCLUSIVE);
/*
* If there are two buffers involved and we pinned just one of them,
* it's possible that the second one became all-visible while we were
* busy pinning the first one. If it looks like that's a possible
* scenario, we'll need to make a second pass through this loop.
*/
if (buffer2 == InvalidBuffer || buffer1 == buffer2
|| (need_to_pin_buffer1 && need_to_pin_buffer2))
break;
}
}
/*
* RelationGetBufferForTuple
*
@ -152,7 +210,7 @@ Buffer
RelationGetBufferForTuple(Relation relation, Size len,
Buffer otherBuffer, int options,
struct BulkInsertStateData * bistate,
Buffer *vmbuffer)
Buffer *vmbuffer, Buffer *vmbuffer_other)
{
bool use_fsm = !(options & HEAP_INSERT_SKIP_FSM);
Buffer buffer = InvalidBuffer;
@ -284,11 +342,17 @@ RelationGetBufferForTuple(Relation relation, Size len,
}
/*
* If the page is all visible but we don't have the right visibility
* map page pinned, then give up our locks, go get the pin, and
* re-lock. This is pretty painful, but hopefully shouldn't happen
* often. Note that there's a small possibility that we didn't pin
* the page above but still have the correct page pinned anyway, either
* We now have the target page (and the other buffer, if any) pinned
* and locked. However, since our initial PageIsAllVisible checks
* were performed before acquiring the lock, the results might now
* be out of date, either for the selected victim buffer, or for the
* other buffer passed by the caller. In that case, we'll need to give
* up our locks, go get the pin(s) we failed to get earlier, and
* re-lock. That's pretty painful, but hopefully shouldn't happen
* often.
*
* Note that there's a small possibility that we didn't pin the
* page above but still have the correct page pinned anyway, either
* because we've already made a previous pass through this loop, or
* because caller passed us the right page anyway.
*
@ -297,19 +361,14 @@ RelationGetBufferForTuple(Relation relation, Size len,
* cleared by some other backend anyway. In that case, we'll have done
* a bit of extra work for no gain, but there's no real harm done.
*/
if (PageIsAllVisible(BufferGetPage(buffer))
&& !visibilitymap_pin_ok(targetBlock, *vmbuffer))
{
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
if (otherBlock != targetBlock)
LockBuffer(otherBuffer, BUFFER_LOCK_UNLOCK);
visibilitymap_pin(relation, targetBlock, vmbuffer);
if (otherBuffer != InvalidBuffer && otherBlock < targetBlock)
LockBuffer(otherBuffer, BUFFER_LOCK_EXCLUSIVE);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
if (otherBuffer != InvalidBuffer && otherBlock > targetBlock)
LockBuffer(otherBuffer, BUFFER_LOCK_EXCLUSIVE);
}
if (otherBuffer == InvalidBuffer || buffer <= otherBuffer)
GetVisibilityMapPins(relation, buffer, otherBuffer,
targetBlock, otherBlock, vmbuffer,
vmbuffer_other);
else
GetVisibilityMapPins(relation, otherBuffer, buffer,
otherBlock, targetBlock, vmbuffer_other,
vmbuffer);
/*
* Now we can check to see if there's enough free space here. If so,

2
src/include/access/hio.h
View File

@ -39,6 +39,6 @@ extern void RelationPutHeapTuple(Relation relation, Buffer buffer,
extern Buffer RelationGetBufferForTuple(Relation relation, Size len,
Buffer otherBuffer, int options,
struct BulkInsertStateData * bistate,
Buffer *vmbuffer);
Buffer *vmbuffer, Buffer *vmbuffer_other);
#endif /* HIO_H */