Re: Small patch for GiST: move childoffnum to child

From: Alexander Korotkov <aekorotkov(at)gmail(dot)com>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
Subject: Re: Small patch for GiST: move childoffnum to child
Date: 2011-07-14 10:29:36
Message-ID: CAPpHfdtYR9DW+P+Pbh6X8BrNWs2sEwEzc+nAeC1D9wZ8Fnzkgg@mail.gmail.com
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On Thu, Jul 14, 2011 at 12:56 PM, Heikki Linnakangas <
heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:

> First, notice that we're setting "ptr->parent = top". 'top' is the current
> node we're processing, and ptr represents the node to the right of the
> current node. The current node is *not* the parent of the node to the right.
> I believe that line should be "ptr->parent = top->parent".
>
I think same.

> Second, we're adding the entry for the right sibling to the end of the list
> of nodes to visit. But when we process entries from the list, we exit
> immediately when we see a leaf page. That means that the right sibling can
> get queued up behind leaf pages, and thus never visited.

I think possible solution is to save right sibling immediatly after current
page . Thus, this code fragment should looks like this:

> if (top->parent && XLByteLT(top->parent->lsn,
> GistPageGetOpaque(page)->nsn) &&
> GistPageGetOpaque(page)->**rightlink !=
> InvalidBlockNumber /* sanity check */ )
> {
> /* page splited while we thinking of... */
> ptr = (GISTInsertStack *) palloc0(sizeof(**
> GISTInsertStack));
> ptr->blkno = GistPageGetOpaque(page)->**rightlink;
> ptr->childoffnum = InvalidOffsetNumber;
> ptr->parent = top->parent;
> ptr->next = top->next;
> top->next = ptr;
> if (tail == top);
> tail = ptr;

}
>

------
With best regards,
Alexander Korotkov.

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