Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commit75f386d

Browse files
committed
Fix two ancient bugs in GiST code to re-find a parent after page split:
First, when following a right-link, we incorrectly marked the current pageas the parent of the right sibling. In reality, the parent of the right pageis the same as the parent of the current page (or some page to the right ofit, gistFindCorrectParent() will sort that out).Secondly, when we follow a right-link, we must prepend, not append, the rightpage to our list of pages to visit. That's because we assume that once wehit a leaf page in the list, all the rest are leaf pages too, and give up.To hit these bugs, you need concurrent actions and several unlucky accidents.Another backend must split the root page, while you're in process ofsplitting a lower-level page. Furthermore, while you scan the internal nodesto re-find the parent, another backend needs to again split some more internalpages. Even then, the bugs don't necessarily manifest as user-visible errorsor index corruption.While we're at it, make the error reporting a bit better if gistFindPath()fails to re-find the parent. It used to be an assertion, but an elog() seemsmore appropriate.Backpatch to all supported branches.
1 parent0dd46a7 commit75f386d

File tree

1 file changed

+24
-9
lines changed

1 file changed

+24
-9
lines changed

‎src/backend/access/gist/gist.c

Lines changed: 24 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -676,24 +676,38 @@ gistFindPath(Relation r, BlockNumber child)
676676

677677
if (GistPageIsLeaf(page))
678678
{
679-
/* we can safety go away, follows only leaf pages */
679+
/*
680+
* Because we scan the index top-down, all the rest of the pages
681+
* in the queue must be leaf pages as well.
682+
*/
680683
UnlockReleaseBuffer(buffer);
681-
returnNULL;
684+
break;
682685
}
683686

684687
top->lsn=PageGetLSN(page);
685688

686689
if (top->parent&&XLByteLT(top->parent->lsn,GistPageGetOpaque(page)->nsn)&&
687690
GistPageGetOpaque(page)->rightlink!=InvalidBlockNumber/* sanity check */ )
688691
{
689-
/* page splited while we thinking of... */
692+
/*
693+
* Page was split while we looked elsewhere. We didn't see the
694+
* downlink to the right page when we scanned the parent, so
695+
* add it to the queue now.
696+
*
697+
* Put the right page ahead of the queue, so that we visit it
698+
* next. That's important, because if this is the lowest internal
699+
* level, just above leaves, we might already have queued up some
700+
* leaf pages, and we assume that there can't be any non-leaf
701+
* pages behind leaf pages.
702+
*/
690703
ptr= (GISTInsertStack*)palloc0(sizeof(GISTInsertStack));
691704
ptr->blkno=GistPageGetOpaque(page)->rightlink;
692705
ptr->childoffnum=InvalidOffsetNumber;
693-
ptr->parent=top;
694-
ptr->next=NULL;
695-
tail->next=ptr;
696-
tail=ptr;
706+
ptr->parent=top->parent;
707+
ptr->next=top->next;
708+
top->next=ptr;
709+
if (tail==top)
710+
tail=ptr;
697711
}
698712

699713
maxoff=PageGetMaxOffsetNumber(page);
@@ -751,7 +765,9 @@ gistFindPath(Relation r, BlockNumber child)
751765
top=top->next;
752766
}
753767

754-
returnNULL;
768+
elog(ERROR,"failed to re-find parent of a page in index \"%s\", block %u",
769+
RelationGetRelationName(r),child);
770+
returnNULL;/* keep compiler quiet */
755771
}
756772

757773

@@ -823,7 +839,6 @@ gistFindCorrectParent(Relation r, GISTInsertStack *child)
823839

824840
/* ok, find new path */
825841
ptr=parent=gistFindPath(r,child->blkno);
826-
Assert(ptr!=NULL);
827842

828843
/* read all buffers as expected by caller */
829844
/* note we don't lock them or gistcheckpage them here! */

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp