/*
* Remove 'node' from the heap. O(log n) amortized.
*/
void
pairingheap_remove(pairingheap *heap, pairingheap_node *node)
{
pairingheap_node *children;
pairingheap_node *replacement;
pairingheap_node *next_sibling;
pairingheap_node **prev_ptr;
/*
* If the removed node happens to be the root node, do it with
* pairingheap_remove_first().
*/
if (node == heap->ph_root)
{
(void) pairingheap_remove_first(heap);
return;
}
/*
* Before we modify anything, remember the removed node's first_child and
* next_sibling pointers.
*/
children = node->first_child;
next_sibling = node->next_sibling;
/*
* Also find the pointer to the removed node in its previous sibling, or
* if this is the first child of its parent, in its parent.
*/
if (node->prev_or_parent->first_child == node)
prev_ptr = &node->prev_or_parent->first_child;
else
prev_ptr = &node->prev_or_parent->next_sibling;
Assert(*prev_ptr == node);
/*
* If this node has children, make a new subheap of the children and link
* the subheap in place of the removed node. Otherwise just unlink this
* node.
*/
if (children)
{
replacement = merge_children(heap, children);
replacement->prev_or_parent = node->prev_or_parent;
replacement->next_sibling = node->next_sibling;
*prev_ptr = replacement;
if (next_sibling)
next_sibling->prev_or_parent = replacement;
}
else
{
*prev_ptr = next_sibling;
if (next_sibling)
next_sibling->prev_or_parent = node->prev_or_parent;
}
}
/*
* Extract next item (in order) from search queue
*
* Returns a GISTSearchItem or NULL. Caller must pfree item when done with it.
*/
static GISTSearchItem *
getNextGISTSearchItem(GISTScanOpaque so)
{
GISTSearchItem *item;
if (!pairingheap_is_empty(so->queue))
{
item = (GISTSearchItem *) pairingheap_remove_first(so->queue);
}
else
{
/* Done when both heaps are empty */
item = NULL;
}
/* Return item; caller is responsible to pfree it */
return item;
}