I ran the following query on Virtuoso:
[code]PREFIX rdf:<http://www.w3.org/1999/02/22-rdf-syntax-ns#>
SELECT DISTINCT ?X
WHERE
{?X rdf:type Musician .
?X rdf:plays <http://Music>}
[/code]
The output of "explain" of this query is:
[code]{
RDF_QUAD_POGS 4 rows(s_1_4_t1.S)
P = ##plays , O = #/Music
RDF_QUAD_POGS 0.8 rows(s_1_4_t0.S)
inlined P = ##type , O = ##Musician , S = s_1_4_t1.S
Distinct (s_1_4_t0.S)
After code:
0: X := := artm s_1_4_t0.S
4: BReturn 0
Subquery Select(X)
After code:
0: X := Call __ro2sq (X)
5: BReturn 0
Select (X)
}
[/code]
Now I am unable to decipher the output of explain command. What do
"ro2sq", "inlined" and "artm" mean? And which join algorithm (like
Hash Join, Merge Join, Nested loop join, etc.) is Virtuoso using for
this query? I need to understand Virtuoso's explain command in order
to understand the reason for Virtuoso taking a long time to execute?
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