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Fix wrong validation of top-parent pointer during page deletion in Btree.

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After introducing usage of t_tid of inner or page high key for storing
number of attributes of tuple, validation of tuple's ItemPointer with
ItemPointerIsValid becomes incorrect, it's need to validate only blocknumber of
ItemPointer. Missing this causes a incorrect page deletion, fix that. Test is
added.

BTW, current contrib/amcheck doesn't fail on index corrupted by this way.

Also introduce BTreeTupleGetTopParent/BTreeTupleSetTopParent macroses to improve
code readability and to avoid possible confusion with page high key: high key
is used to store top-parent link for branch to remove.

Bug found by Michael Paquier, but bug doesn't exist in previous versions because
t_tid was set to P_HIKEY.

Author: Teodor Sigaev
Reviewer: Peter Geoghegan
Discussion: https://www.postgresql.org/message-id/flat/20180419052436.GA16000%40paquier.xyz
This commit is contained in:
Teodor Sigaev
2018-04-23 15:55:10 +03:00
parent 6a7b2ce2bd
commit 6db4b49986
6 changed files with 46 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

21
src/backend/access/nbtree/nbtpage.c
View File

@@ -1602,10 +1602,9 @@ _bt_mark_page_halfdead(Relation rel, Buffer leafbuf, BTStack stack)
MemSet(&trunctuple, 0, sizeof(IndexTupleData));
trunctuple.t_info = sizeof(IndexTupleData);
if (target != leafblkno)
ItemPointerSetBlockNumber(&trunctuple.t_tid, target);
BTreeTupleSetTopParent(&trunctuple, target);
else
ItemPointerSetInvalid(&trunctuple.t_tid);
BTreeTupleSetNAtts(&trunctuple, 0);
BTreeTupleSetTopParent(&trunctuple, InvalidBlockNumber);
if (PageAddItem(page, (Item) &trunctuple, sizeof(IndexTupleData), P_HIKEY,
false, false) == InvalidOffsetNumber)
@@ -1690,7 +1689,7 @@ _bt_unlink_halfdead_page(Relation rel, Buffer leafbuf, bool *rightsib_empty)
BTPageOpaque opaque;
bool rightsib_is_rightmost;
int targetlevel;
ItemPointer leafhikey;
IndexTuple leafhikey;
BlockNumber nextchild;
page = BufferGetPage(leafbuf);
@@ -1702,7 +1701,7 @@ _bt_unlink_halfdead_page(Relation rel, Buffer leafbuf, bool *rightsib_empty)
* Remember some information about the leaf page.
*/
itemid = PageGetItemId(page, P_HIKEY);
leafhikey = &((IndexTuple) PageGetItem(page, itemid))->t_tid;
leafhikey = (IndexTuple) PageGetItem(page, itemid);
leafleftsib = opaque->btpo_prev;
leafrightsib = opaque->btpo_next;
@@ -1714,9 +1713,10 @@ _bt_unlink_halfdead_page(Relation rel, Buffer leafbuf, bool *rightsib_empty)
* parent in the branch. Set 'target' and 'buf' to reference the page
* actually being unlinked.
*/
if (ItemPointerIsValid(leafhikey))
target = BTreeTupleGetTopParent(leafhikey);
if (target != InvalidBlockNumber)
{
target = ItemPointerGetBlockNumberNoCheck(leafhikey);
Assert(target != leafblkno);
/* fetch the block number of the topmost parent's left sibling */
@@ -1919,12 +1919,7 @@ _bt_unlink_halfdead_page(Relation rel, Buffer leafbuf, bool *rightsib_empty)
* branch.
*/
if (target != leafblkno)
{
if (nextchild == InvalidBlockNumber)
ItemPointerSetInvalid(leafhikey);
else
ItemPointerSetBlockNumber(leafhikey, nextchild);
}
BTreeTupleSetTopParent(leafhikey, nextchild);
/*
* Mark the page itself deleted. It can be recycled when all current

12
src/backend/access/nbtree/nbtxlog.c
View File

@@ -800,11 +800,7 @@ btree_xlog_mark_page_halfdead(uint8 info, XLogReaderState *record)
*/
MemSet(&trunctuple, 0, sizeof(IndexTupleData));
trunctuple.t_info = sizeof(IndexTupleData);
if (xlrec->topparent != InvalidBlockNumber)
ItemPointerSetBlockNumber(&trunctuple.t_tid, xlrec->topparent);
else
ItemPointerSetInvalid(&trunctuple.t_tid);
BTreeTupleSetNAtts(&trunctuple, 0);
BTreeTupleSetTopParent(&trunctuple, xlrec->topparent);
if (PageAddItem(page, (Item) &trunctuple, sizeof(IndexTupleData), P_HIKEY,
false, false) == InvalidOffsetNumber)
@@ -912,11 +908,7 @@ btree_xlog_unlink_page(uint8 info, XLogReaderState *record)
/* Add a dummy hikey item */
MemSet(&trunctuple, 0, sizeof(IndexTupleData));
trunctuple.t_info = sizeof(IndexTupleData);
if (xlrec->topparent != InvalidBlockNumber)
ItemPointerSetBlockNumber(&trunctuple.t_tid, xlrec->topparent);
else
ItemPointerSetInvalid(&trunctuple.t_tid);
BTreeTupleSetNAtts(&trunctuple, 0);
BTreeTupleSetTopParent(&trunctuple, xlrec->topparent);
if (PageAddItem(page, (Item) &trunctuple, sizeof(IndexTupleData), P_HIKEY,
false, false) == InvalidOffsetNumber)