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Date: Tue, 04 May 2010 22:56:42 +0200
From: Frank Wesemann <f.wesemann@fotofinder.net>
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To: solr-user@lucene.apache.org
Subject: inconsistency in SolrParams.get()
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Dear list,
I recently stumpled upon this:

modifiableParams = new ModifiableSolrParams( req.getParams() );

assert modifiableParams.get("key").equals( req.getParams().get("key") );

this test fails for requests built from a SimpleRequestParser or 
StandardRequestParser where the parameter "key" was given, but empty ( 
e.g. localhost:8393/select/?key=&para1=val1&parm2=val2 ).

The reason is that oas.request.ServletSolrParams returns null for values 
with length() == 0,
but all other SolrParams implementations return the empty String.

This behaviour has also side effects on search components:
Most, if not all, standard search components check for something like

if (reg.getParams().getBool(myTriggerParameter, false) ) {

    ...do what I am supposed to do...

}


In case of ServletSolrParams getBool() returns the desired and expected 
"false",
all other Implementations throw a "bad request" Exception.
One may argue that suppling a parameter with an empty value indeed is a 
malformed request,
but as an example, in our frontend servers we use a Perllib which always 
adds the "q" parameter to a SolrRequest
( and our Solr implementation allows  requests without a explicit query ).

Nonetheless I think, the above mentioned equality check should hold true 
for any request and any SolrParams.
Because I cannot oversee the implications, I currently don't have a 
better suggestion to achieve this, than
to make ServleSolrParams also return the empty String, which is in my 
opinion counter-intuitive and does not the right thing for the 
getBool(), getInt() etc. cases.
Any thoughts?

 btw:
is ModifiableSolrParams.set(key, null) removes key from the params 
really the desired and expected behaviour?

 
-- 
mit freundlichem Gruß,

Frank Wesemann
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