Re: cvs head initdb hangs on unixware

Hi Tom,
On Mon, 8 Dec 2008, Tom Lane wrote:

> Date: Mon, 08 Dec 2008 13:15:28 -0500
> From: Tom Lane <tgl@sss.pgh.pa.us>
> To: ohp@pyrenet.fr
> Cc: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>,
>     Zdenek Kotala <Zdenek.Kotala@Sun.COM>,
>     pgsql-hackers list <pgsql-hackers@postgresql.org>
> Subject: Re: [HACKERS] cvs head initdb hangs on unixware 
> 
> ohp@pyrenet.fr writes:
>> the infinite loop occurs in fsm_search_avail when called for the 32nd
>> time.
>
> ... which is the first time that the initial test doesn't make it fall
> out immediately.
>
> Would you add a couple more printouts, along the line of
>
>
> 	nodeno = target;
> 	while (nodeno > 0)
> 	{
> +		fprintf(stderr, "ascend at node %d value %d\n",
> +			nodeno, fsmpage->fp_nodes[nodeno]);
>
> 		if (fsmpage->fp_nodes[nodeno] >= minvalue)
> 			break;
>
> 		/*
> 		 * Move to the right, wrapping around on same level if necessary,
> 		 * then climb up.
> 		 */
> 		nodeno = parentof(rightneighbor(nodeno));
> 	}
>
> 	/*
> 	 * We're now at a node with enough free space, somewhere in the middle of
> 	 * the tree. Descend to the bottom, following a path with enough free
> 	 * space, preferring to move left if there's a choice.
> 	 */
> 	while (nodeno < NonLeafNodesPerPage)
> 	{
> 		int leftnodeno = leftchild(nodeno);
> 		int rightnodeno = leftnodeno + 1;
> 		bool leftok = (leftnodeno < NodesPerPage) &&
> 			(fsmpage->fp_nodes[leftnodeno] >= minvalue);
> 		bool rightok = (rightnodeno < NodesPerPage) &&
> 			(fsmpage->fp_nodes[rightnodeno] >= minvalue);
>
> +		fprintf(stderr, "descend at node %d value %d, leftnode %d value %d, rightnode %d value %d\n",
> +			nodeno, fsmpage->fp_nodes[nodeno],
> +			leftnodeno, fsmpage->fp_nodes[leftnodeno],
> +			rightnodeno, fsmpage->fp_nodes[rightnodeno]);
>
> 		if (leftok)
> 			nodeno = leftnodeno;
> 		else if (rightok)
> 			nodeno = rightnodeno;
> 		else
>
> (I'm assuming we can print possibly-off-the-end array elements without dumping
> core; which is bogus in general but I expect we can get away with it
> for this purpose.)
>
> Also, we don't really need 94MB of log to convince us it's an
> infinite loop ;-)
oops, sorry
>
> 			regards, tom lane
>
I first misread your mail, and added only the first fprintf , while I was 
uploading a 400M initdb.log, I went back to add the second one.

Guess what! with the fprintf .. descending node... in place, everything 
goes well. The optimizer definitly does something weird along the 
definition/assignement of leftok/rightok..


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