On Mon, Apr 19, 2021 at 8:04 PM Bharath Rupireddy
<bharath.rupireddyforpostg...@gmail.com> wrote:
>
> On Mon, Apr 19, 2021 at 1:57 PM Masahiko Sawada <sawada.m...@gmail.com> wrote:
> >
> > On Mon, Apr 19, 2021 at 5:04 PM Kyotaro Horiguchi
> > <horikyota....@gmail.com> wrote:
> > >
> > > At Mon, 19 Apr 2021 13:32:31 +0900, Masahiko Sawada
> > > <sawada.m...@gmail.com> wrote in
> > > > On Fri, Apr 16, 2021 at 12:16 PM Kyotaro Horiguchi
> > > > <horikyota....@gmail.com> wrote:
> > > > > AFAICS the page is always empty when RelationGetBufferForTuple
> > > > > returned a valid vmbuffer. So the "if" should be an "assert" instead.
> > > >
> > > > There is a chance that RelationGetBufferForTuple() returns a valid
> > > > vmbuffer but the page is not empty, since RelationGetBufferForTuple()
> > > > checks without a lock if the page is empty. But when it comes to
> > > > HEAP_INSERT_FROZEN cases it actually doesn’t happen at least for now
> > > > since only one process inserts tuples into the relation. Will fix.
> > >
> > > Yes. It seems to me that it is cleaner that RelationGetBufferForTuple
> > > returns vmbuffer only when the caller needs to change vm state.
> > > Thanks.
> > >
> > > > > And, the patch changes the value of all_frozen_set to false when the
> > > > > page was already all-frozen (thus not empty). It would be fine since
> > > > > we don't need to change the visibility of the page in that case but
> > > > > the variable name is no longer correct. set_all_visible or such?
> > > >
> > > > It seems to me that the variable name all_frozen_set corresponds to
> > > > XLH_INSERT_ALL_FROZEN_SET but I see your point. How about
> > > > set_all_frozen instead since we set all-frozen bits (also implying
> > > > setting all-visible)?
> > >
> > > Right. However, "if (set_all_frozen) then "set all_visible" looks like
> > > a bug^^;. all_frozen_set looks better in that context than
> > > set_all_frozen. So I withdraw the comment.
> > >
> > > > BTW I found the following description of XLH_INSERT_ALL_FROZEN_SET but
> > > > there is no all_visible_set anywhere:
> > > >
> > > > /* all_frozen_set always implies all_visible_set */
> > > > #define XLH_INSERT_ALL_FROZEN_SET (1<<5)
> > > >
> > > > I'll update those comments as well.
> > >
> > > FWIW, it seems like a shorthand of "ALL_FROZEN_SET implies ALL_VISIBLE
> > > to be set together". The current comment is working to me.
> > >
> >
> > Okay, I've updated the patch accordingly. Please review it.
>
> I was reading the patch, just found some typos: it should be "a frozen
> tuple" not "an frozen tuple".
>
> + * Also pin visibility map page if we're inserting an frozen tuple into
> + * If we're inserting an frozen entry into empty page, pin
> the
Thank you for the comment.
I’ve updated the patch including the above comment.
Regards,
--
Masahiko Sawada
EDB: https://www.enterprisedb.com/
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 13396eb7f2..65ec6118b9 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -2065,7 +2065,6 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
Buffer buffer;
Page page = NULL;
Buffer vmbuffer = InvalidBuffer;
- bool starting_with_empty_page;
bool all_visible_cleared = false;
bool all_frozen_set = false;
uint8 vmstatus = 0;
@@ -2082,8 +2081,8 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
* Find buffer to insert this tuple into. If the page is all visible,
* this will also pin the requisite visibility map page.
*
- * Also pin visibility map page if COPY FREEZE inserts tuples into an
- * empty page. See all_frozen_set below.
+ * Also pin visibility map page if we're inserting a frozen tuple into
+ * an empty page. See all_frozen_set below.
*/
buffer = RelationGetBufferForTuple(relation, heaptup->t_len,
InvalidBuffer, options, bistate,
@@ -2093,22 +2092,23 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
/*
* If we're inserting frozen entry into an empty page,
* set visibility map bits and PageAllVisible() hint.
- *
- * If we're inserting frozen entry into already all_frozen page,
- * preserve this state.
*/
- if (options & HEAP_INSERT_FROZEN)
+ if (options & HEAP_INSERT_FROZEN && BufferIsValid(vmbuffer))
{
- page = BufferGetPage(buffer);
+ Assert(visibilitymap_pin_ok(BufferGetBlockNumber(buffer), vmbuffer));
- starting_with_empty_page = PageGetMaxOffsetNumber(page) == 0;
+ page = BufferGetPage(buffer);
+ vmstatus = visibilitymap_get_status(relation,
+ BufferGetBlockNumber(buffer), &vmbuffer);
- if (visibilitymap_pin_ok(BufferGetBlockNumber(buffer), vmbuffer))
- vmstatus = visibilitymap_get_status(relation,
- BufferGetBlockNumber(buffer), &vmbuffer);
+ /* The page must be empty */
+ Assert(PageGetMaxOffsetNumber(page) == 0);
- if ((starting_with_empty_page || vmstatus & VISIBILITYMAP_ALL_FROZEN))
- all_frozen_set = true;
+ /*
+ * If we're inserting frozen entry into empty page, we will set
+ * all-visible to page and all-frozen on visibility map.
+ */
+ all_frozen_set = true;
}
/*
diff --git a/src/backend/access/heap/hio.c b/src/backend/access/heap/hio.c
index ffc89685bf..420503725c 100644
--- a/src/backend/access/heap/hio.c
+++ b/src/backend/access/heap/hio.c
@@ -301,6 +301,13 @@ RelationAddExtraBlocks(Relation relation, BulkInsertState bistate)
* Note that in some cases the caller might have already acquired such pins,
* which is indicated by these arguments not being InvalidBuffer on entry.
*
+ * In HEAP_INSERT_FROZEN cases, we handle the possibility that the caller will
+ * sets all-frozen bit on the visibility map page. We pin on the visibility
+ * map page so that the caller can set the bit later, only if the page is
+ * empty. If the page is all-visible, we skip getting a pin on the
+ * visibility map page while assuming the caller will neither clear nor set
+ * the bit on the page.
+ *
* We normally use FSM to help us find free space. However,
* if HEAP_INSERT_SKIP_FSM is specified, we just append a new empty page to
* the end of the relation if the tuple won't fit on the current target page.
@@ -425,6 +432,8 @@ RelationGetBufferForTuple(Relation relation, Size len,
loop:
while (targetBlock != InvalidBlockNumber)
{
+ bool skip_vmbuffer = false;
+
/*
* Read and exclusive-lock the target block, as well as the other
* block if one was given, taking suitable care with lock ordering and
@@ -442,14 +451,28 @@ loop:
{
/* easy case */
buffer = ReadBufferBI(relation, targetBlock, RBM_NORMAL, bistate);
- if (PageIsAllVisible(BufferGetPage(buffer)))
- visibilitymap_pin(relation, targetBlock, vmbuffer);
- /*
- * If the page is empty, pin vmbuffer to set all_frozen bit later.
- */
- if ((options & HEAP_INSERT_FROZEN) &&
- (PageGetMaxOffsetNumber(BufferGetPage(buffer)) == 0))
+ if (options & HEAP_INSERT_FROZEN)
+ {
+ /*
+ * If we're inserting a frozen entry into empty page, pin on the
+ * visibility map buffer to set all_frozen bit later. Note that
+ * we check without a buffer lock if the page is empty but the
+ * caller doesn't need to recheck that since we assume that in
+ * HEAP_INSERT_FROZEN case, only one process is inserting a
+ * frozen tuple into this relation.
+ *
+ * If the page already is non-empty and all-visible, we skip to
+ * pin on a visibility map buffer since we never clear and set
+ * all-frozen bit on visibility map during inserting a frozen
+ * tuple.
+ */
+ if (PageGetMaxOffsetNumber(BufferGetPage(buffer)) == 0)
+ visibilitymap_pin(relation, targetBlock, vmbuffer);
+ else if (PageIsAllVisible(BufferGetPage(buffer)))
+ skip_vmbuffer = true;
+ }
+ else if (PageIsAllVisible(BufferGetPage(buffer)))
visibilitymap_pin(relation, targetBlock, vmbuffer);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
@@ -502,7 +525,13 @@ loop:
* done a bit of extra work for no gain, but there's no real harm
* done.
*/
- if (otherBuffer == InvalidBuffer || targetBlock <= otherBlock)
+ if (skip_vmbuffer)
+ {
+ /* We must be inserting a frozen tuple into the all-visible page */
+ Assert(options & HEAP_INSERT_FROZEN);
+ Assert(PageIsAllVisible(BufferGetPage(buffer)));
+ }
+ else if (otherBuffer == InvalidBuffer || targetBlock <= otherBlock)
GetVisibilityMapPins(relation, buffer, otherBuffer,
targetBlock, otherBlock, vmbuffer,
vmbuffer_other);
@@ -517,6 +546,18 @@ loop:
*/
page = BufferGetPage(buffer);
+#ifdef USE_ASSERT_CHECKING
+ /*
+ * If we pin on the visibility map when inserting a frozen tuple,
+ * the page must still be empty.
+ */
+ if ((options & HEAP_INSERT_FROZEN) && BufferIsValid(*vmbuffer))
+ {
+ Assert(PageGetMaxOffsetNumber(page) == 0);
+ Assert(!BufferIsValid(*vmbuffer_other));
+ }
+#endif
+
/*
* If necessary initialize page, it'll be used soon. We could avoid
* dirtying the buffer here, and rely on the caller to do so whenever
