/*
* Form a downlink pointer for the page in 'buf'.
*/
static IndexTuple
gistformdownlink(Relation rel, Buffer buf, GISTSTATE *giststate,
GISTInsertStack *stack)
{
Page page = BufferGetPage(buf);
OffsetNumber maxoff;
OffsetNumber offset;
IndexTuple downlink = NULL;
maxoff = PageGetMaxOffsetNumber(page);
for (offset = FirstOffsetNumber; offset <= maxoff; offset = OffsetNumberNext(offset))
{
IndexTuple ituple = (IndexTuple)
PageGetItem(page, PageGetItemId(page, offset));
if (downlink == NULL)
downlink = CopyIndexTuple(ituple);
else
{
IndexTuple newdownlink;
newdownlink = gistgetadjusted(rel, downlink, ituple,
giststate);
if (newdownlink)
downlink = newdownlink;
}
}
/*
* If the page is completely empty, we can't form a meaningful downlink
* for it. But we have to insert a downlink for the page. Any key will do,
* as long as its consistent with the downlink of parent page, so that we
* can legally insert it to the parent. A minimal one that matches as few
* scans as possible would be best, to keep scans from doing useless work,
* but we don't know how to construct that. So we just use the downlink of
* the original page that was split - that's as far from optimal as it can
* get but will do..
*/
if (!downlink)
{
ItemId iid;
LockBuffer(stack->parent->buffer, GIST_EXCLUSIVE);
gistFindCorrectParent(rel, stack);
iid = PageGetItemId(stack->parent->page, stack->downlinkoffnum);
downlink = (IndexTuple) PageGetItem(stack->parent->page, iid);
downlink = CopyIndexTuple(downlink);
LockBuffer(stack->parent->buffer, GIST_UNLOCK);
}
ItemPointerSetBlockNumber(&(downlink->t_tid), BufferGetBlockNumber(buf));
GistTupleSetValid(downlink);
return downlink;
}
/*
* Updates the stack so that child->parent is the correct parent of the
* child. child->parent must be exclusively locked on entry, and will
* remain so at exit, but it might not be the same page anymore.
*/
static void
gistFindCorrectParent(Relation r, GISTInsertStack *child)
{
GISTInsertStack *parent = child->parent;
gistcheckpage(r, parent->buffer);
parent->page = (Page) BufferGetPage(parent->buffer);
/* here we don't need to distinguish between split and page update */
if (child->downlinkoffnum == InvalidOffsetNumber ||
parent->lsn != PageGetLSN(parent->page))
{
/* parent is changed, look child in right links until found */
OffsetNumber i,
maxoff;
ItemId iid;
IndexTuple idxtuple;
GISTInsertStack *ptr;
while (true)
{
maxoff = PageGetMaxOffsetNumber(parent->page);
for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
{
iid = PageGetItemId(parent->page, i);
idxtuple = (IndexTuple) PageGetItem(parent->page, iid);
if (ItemPointerGetBlockNumber(&(idxtuple->t_tid)) == child->blkno)
{
/* yes!!, found */
child->downlinkoffnum = i;
return;
}
}
parent->blkno = GistPageGetOpaque(parent->page)->rightlink;
UnlockReleaseBuffer(parent->buffer);
if (parent->blkno == InvalidBlockNumber)
{
/*
* End of chain and still didn't find parent. It's a very-very
* rare situation when root splited.
*/
break;
}
parent->buffer = ReadBuffer(r, parent->blkno);
LockBuffer(parent->buffer, GIST_EXCLUSIVE);
gistcheckpage(r, parent->buffer);
parent->page = (Page) BufferGetPage(parent->buffer);
}
/*
* awful!!, we need search tree to find parent ... , but before we
* should release all old parent
*/
ptr = child->parent->parent; /* child->parent already released
* above */
while (ptr)
{
ReleaseBuffer(ptr->buffer);
ptr = ptr->parent;
}
/* ok, find new path */
ptr = parent = gistFindPath(r, child->blkno, &child->downlinkoffnum);
/* read all buffers as expected by caller */
/* note we don't lock them or gistcheckpage them here! */
while (ptr)
{
ptr->buffer = ReadBuffer(r, ptr->blkno);
ptr->page = (Page) BufferGetPage(ptr->buffer);
ptr = ptr->parent;
}
/* install new chain of parents to stack */
child->parent = parent;
/* make recursive call to normal processing */
LockBuffer(child->parent->buffer, GIST_EXCLUSIVE);
gistFindCorrectParent(r, child);
}
return;
}
void
gistmakedeal(GISTInsertState *state, GISTSTATE *giststate)
{
int is_splitted;
ItemId iid;
IndexTuple oldtup,
newtup;
MIRROREDLOCK_BUFMGR_MUST_ALREADY_BE_HELD;
/* walk up */
while (true)
{
/*
* After this call: 1. if child page was splited, then itup contains
* keys for each page 2. if child page wasn't splited, then itup
* contains additional for adjustment of current key
*/
if (state->stack->parent)
{
/*
* X-lock parent page before proceed child, gistFindCorrectParent
* should find and lock it
*/
gistFindCorrectParent(state->r, state->stack);
}
is_splitted = gistplacetopage(state, giststate);
/* parent locked above, so release child buffer */
UnlockReleaseBuffer(state->stack->buffer);
/* pop parent page from stack */
state->stack = state->stack->parent;
/* stack is void */
if (!state->stack)
break;
/*
* child did not split, so we can check is it needed to update parent
* tuple
*/
if (!is_splitted)
{
/* parent's tuple */
iid = PageGetItemId(state->stack->page, state->stack->childoffnum);
oldtup = (IndexTuple) PageGetItem(state->stack->page, iid);
newtup = gistgetadjusted(state->r, oldtup, state->itup[0], giststate);
if (!newtup)
{ /* not need to update key */
LockBuffer(state->stack->buffer, GIST_UNLOCK);
break;
}
state->itup[0] = newtup;
}
} /* while */
/* release all parent buffers */
while (state->stack)
{
ReleaseBuffer(state->stack->buffer);
state->stack = state->stack->parent;
}
/* say to xlog that insert is completed */
if (state->needInsertComplete && !state->r->rd_istemp)
gistxlogInsertCompletion(state->r->rd_node, &(state->key), 1);
}
