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Fix yet another crash in page split during GiST index creation. 

Commit a7ee7c8513 fixed a bug in GiST page split during index creation,
where we failed to re-find the position of a downlink after the page
containing it was split. However, that fix was incomplete; the other call
to gistinserttuples() in the same function needs to also clear
'downlinkoffnum'.

Fixes bug #16134 reported by Alexander Lakhin, for real this time. The
previous fix was enough to fix the crash with the reproducer script for
bug #16162, but the original script for #16134 was still crashing.

Backpatch to v12, like the previous incomplete fix.

Discussion: https://www.postgresql.org/message-id/d869f537-abe4-d2ea-0510-38cd053f5152%40gmail.com
This commit is contained in:
Heikki Linnakangas 2019-12-16 13:57:41 +02:00
parent 502423180a
commit 741b884353
1 changed files with 19 additions and 12 deletions
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31
src/backend/access/gist/gist.c
View File

@ -1325,10 +1325,9 @@ gistfinishsplit(GISTInsertState *state, GISTInsertStack *stack,
* downlink for the original page as one operation.
*/
LockBuffer(stack->parent->buffer, GIST_EXCLUSIVE);
gistFindCorrectParent(state->r, stack);
/*
* insert downlinks for the siblings from right to left, until there are
* Insert downlinks for the siblings from right to left, until there are
* only two siblings left.
*/
for (int pos = list_length(splitinfo) - 1; pos > 1; pos--)
@ -1336,17 +1335,17 @@ gistfinishsplit(GISTInsertState *state, GISTInsertStack *stack,
right = (GISTPageSplitInfo *) list_nth(splitinfo, pos);
left = (GISTPageSplitInfo *) list_nth(splitinfo, pos - 1);
gistFindCorrectParent(state->r, stack);
if (gistinserttuples(state, stack->parent, giststate,
&right->downlink, 1,
InvalidOffsetNumber,
left->buf, right->buf, false, false))
{
/*
* If the parent page was split, need to relocate the original
* parent pointer.
* If the parent page was split, the existing downlink might
* have moved.
*/
stack->downlinkoffnum = InvalidOffsetNumber;
gistFindCorrectParent(state->r, stack);
}
/* gistinserttuples() released the lock on right->buf. */
}
@ -1361,13 +1360,21 @@ gistfinishsplit(GISTInsertState *state, GISTInsertStack *stack,
*/
tuples[0] = left->downlink;
tuples[1] = right->downlink;
gistinserttuples(state, stack->parent, giststate,
tuples, 2,
stack->downlinkoffnum,
left->buf, right->buf,
true, /* Unlock parent */
unlockbuf /* Unlock stack->buffer if caller wants that */
);
gistFindCorrectParent(state->r, stack);
if (gistinserttuples(state, stack->parent, giststate,
tuples, 2,
stack->downlinkoffnum,
left->buf, right->buf,
true, /* Unlock parent */
unlockbuf /* Unlock stack->buffer if caller wants that */
))
{
/*
* If the parent page was split, the downlink might have moved.
*/
stack->downlinkoffnum = InvalidOffsetNumber;
}
Assert(left->buf == stack->buffer);
/*