Identifying the existence of a document

, ,
1

Hi,

Is there an efficient way to identify the existence of a document.

I have tried something like


HttpURLConnection req = (HttpURLConnection) new URL().openConnection();
req.setRequestMethod(“HEAD”);
…
req.connect();
exist = req.getResponseCode == 200;


but that only works if you request a document via its document id, e.g. http://hostname/tamino/mydb/mycoll/mydoc/@1.


Another approach I have tried was to use _admin=ino:DisplayIndex(…) on a data index and requesting only one value (and checking if the start value equals the outcome), but during my performance tests I noticed that the performance is worser then using a plain “GET”.

Actually I would like to use a HEAD HTTP request using an _xql request and I want Tamino to respond with HTTP response code 200 indicating that something has been found (that is all I want!).

This will eliminate the overhead of InputStreams that need to be read in order to determine if something exists.

Kind regards,
Rudolf de Grijs

2

Hi Rudolf,

What are you asking for is not possible with HTTP HEAD because you get back 404. Can I suggest the following. Assume the query is something like a[@name=“a”] in the ino:etc collection and you just want to know if document(s) exist or not, then you could issue something like:

_xql(0,1)=a[@name=“a”]/@ino:id

This will return a body (the tamino response) with the ‘a’ element in this case and the ino:id attribute and non of its descendant children. So if a was a very large document, none of it is returned. So the response from Tamino is small and you can test the existance of the xql:result element. If this exists document(s) exist otherwise the query was negative and there are no documents.

Does this help?

Stuart Fyffe-Collins
Software AG (UK) Ltd.

3

Thanks Stuart! Your answer is clear.

BTW I thought that the _xql(0,1) would be deprecated in the future (so I guess that the new cursoring mechanism will be more appropriate).

I think that it might be worthwhile to have something like an _exist X-machine command (which could e.g. only be combined with HTTP HEAD request).

Regards,
Rudolf

4

Hello Guys.

An alternative is to use this query:

  _xql=boolean(a[@name="a"])


This will always return a result of TRUE (if there is a document matching the filter) or FALSE (if there is no match).

Greetings,
Trevor.