Re: [Virtuoso-users] SPARQL processor sensitive to text length of queries.

[David B. <d.b...@au...>]

Hi Hugh,

I had this as two curl commands, one that returned an empty result set, 
the other good, then tried using trace_on() to see if anything showed. 
Nothing apparent in the log files so restarted Virtuoso in the 
foreground and of course the problem went away. I did try your query 
(before the restart) and that was fine.

I will keep an eye on things and if something similar occurs I'll 
investigate without restarting the server.

Are there any options, possibly compiled in, that will log all 
translated SPARQL? And execution plans?? I'm happy to have a diagnostic 
build running in case whatever it was reoccurs.


Thanks,
Dave


On 5/10/12 4:11 PM, Hugh Williams wrote:
> Hi David,
>
> You can use the Virtuoso explain() function to obtain the query 
> execution plan:
>
> http://docs.openlinksw.com/virtuoso/fn_explain.html
>
> There is also a sparql_to_sql_text function:
>
> http://docs.openlinksw.com/virtuoso/fn_sparql_to_sql_text.html
>
> As well as the trace_on() function which can log various server 
> operations specified when enabling it:
>
> http://docs.openlinksw.com/virtuoso/fn_trace_on.html
>
> Have you tried running my query on your system to see if it has a 
> similar problem ?
>
> Best Regards
> Hugh Williams
> Professional Services
> OpenLink Software, Inc.      // http://www.openlinksw.com/
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>
> On 4 Oct 2012, at 22:23, David Brooks wrote:
>
>> Hi Hugh,
>>
>> I noticed things weren't right using the SPARQL endpoint so cut and 
>> pasted the query into Conductor's interface. It behaves properly with 
>> isql.
>>
>> I have had issues (using /sparql) with textually long queries that 
>> returned empty result sets, so tried adding newlines at appropriate 
>> places as I constructed the query and all was well.
>>
>> Back to this particular query, and in Conductor, it can be made to 
>> work by adding/removing whitespace anywhere, even at the end. At also 
>> works if the "100" is changed to "101" with the whitespace unchanged.
>>
>> The failing query (enclosed in brackets) is:
>>
>> [select distinct ?g where { graph 
>> <http://demo.biosignalml.org/provenance> {
>>                               ?g dct:subject 
>> <http://demo.biosignalml.org/resource/physiobank/mitdb/100>
>>                               } } order by ?g]
>>
>> I see (by Javascript debugging) that Conductor encodes the query and 
>> sends it to /sparql -- I now have the body which is POSTed, so will 
>> carry on investigating later. Are there debugging options that can be 
>> enabled for queries submitted to /sparql ? Is it possible to log the 
>> generated SQL ??
>>
>>
>> Thanks,
>> Dave
>>
>>
>>
>> On 5/10/12 2:25 AM, Hugh Williams wrote:
>>> Hi David,
>>>
>>> I am unable to recreate this issue, as with one, two or no space a 
>>> query of a similar form works for me. Actually try it on your 
>>> instance as it is against one of the system graphs:
>>>
>>> SELECT distinct ?s where { graph 
>>> <http://www.openlinksw.com/schemas/virtrdf#> {?s virtrdf:item 
>>> <http://www.openlinksw.com/virtrdf-data-formats#default-iid> }} 
>>> order by ?s
>>>
>>> Also, I note you are using the internal sparql query interface of 
>>> the conductor, does the problem occur when you run the same query 
>>> against the SPARQL endpoint (/sparql) or via the isql interface 
>>> (either from commandline or conductor) ?
>>>
>>> Best Regards
>>> Hugh Williams
>>> Professional Services
>>> OpenLink Software, Inc.  // http://www.openlinksw.com/
>>> Weblog   -- http://www.openlinksw.com/blogs/
>>> LinkedIn -- http://www.linkedin.com/company/openlink-software/
>>> Twitter  -- http://twitter.com/OpenLink
>>> Google+  -- http://plus.google.com/100570109519069333827/
>>> Facebook -- http://www.facebook.com/OpenLinkSoftware
>>> Universal Data Access, Integration, and Management Technology Providers
>>>
>>> On 4 Oct 2012, at 04:29, David Brooks wrote:
>>>
>>>> Hi,
>>>>
>>>> Following are two screen shots showing queries and their result 
>>>> sets -- the only difference between the first and the second is an 
>>>> extra space before the word "graph". The second query has the 
>>>> correct result set. This is from 32-bit Virtuoso under Centos. (And 
>>>> in relation to my other issue, the "doc" package is not installed).
>>>>
>>>>
>>>> Thanks,
>>>> Dave
>>>>
>>>>
>>>> <Screen shot 2012-10-04 at 3.55.10 PM.png>
>>>>
>>>> <Screen shot 2012-10-04 at 3.55.36 PM.png>
>>>>
>>>>
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>>
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