Hi Patrick,

Internally the representation of collections and documents is almost identical. All documents of a collection are stored in a single table. With respect to updates there should be no big difference.

The only benefit of a collection of documents is the direct access to the documents by their name. If you don't access the documents by name but by their molecule-id attribute then one big document might be an alternative.

Jan

On Jun 17, 2010, at 10:34, Patrick Schäfer wrote:

Hi Jan,

thank you for your response. I thought that all documents within a collection are stored within one (or several) relational tables?

I am not sure, if merging all documents into one big document is an option. The documents are supposed to be updateable ... does that give a good performance for one large document?

Patrick



Message: 7
Date: Tue, 15 Jun 2010 21:58:44 +0200
From: Jan Rittinger <jan.rittinger@uni-tuebingen.de>
Subject: Re: [MonetDB-users] MonetDB XML - slow execution of query
	with test	on attribute
To: Communication channel for MonetDB users
	<monetdb-users@lists.sourceforge.net>
Message-ID: <702CE627-774E-47C5-B3B7-34A5431F20CF@uni-tuebingen.de>
Content-Type: text/plain; charset="windows-1252"

Hi Patrick,

the evaluation plan of your query looks quite bad -- with respect to what could be possible...

If you could use 'doc("tu")' (with a single big document containing all small documents), you would get the result in *no* time, as then the attribute index is used. Unfortunately I'm not aware of the difference in the attribute index with respect to collections...

Regards,
Jan

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Jan Rittinger
Lehrstuhl Datenbanken und Informationssysteme
Wilhelm-Schickard-Institut für Informatik
Eberhard-Karls-Universität Tübingen