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1
6
7 package com.hp.hpl.jena.graph.query;
8
9 import java.util.*;
10
11 import com.hp.hpl.jena.graph.*;
12 import com.hp.hpl.jena.util.iterator.*;
13
14
19 public class SimpleQueryEngine
20 {
21 private ExpressionSet constraint;
22 private NamedTripleBunches triples;
23 private TripleSorter sortMethod;
24 private int variableCount;
25
26 public SimpleQueryEngine( NamedTripleBunches triples, TripleSorter ts, ExpressionSet constraint )
27 { this.constraint = constraint;
28 this.triples = triples;
29 this.sortMethod = ts; }
30
31 int getVariableCount()
32 { return variableCount; }
33
34 public ExtendedIterator executeBindings( List outStages, NamedGraphMap args, Node [] nodes )
35 {
36 Mapping map = new Mapping( nodes );
37 ArrayList stages = new ArrayList();
38 addStages( stages, args, map );
39 if (constraint.isComplex()) stages.add( new ConstraintStage( map, constraint ) );
40 outStages.addAll( stages );
41 variableCount = map.size();
42 return filter( connectStages( stages, variableCount ) );
43 }
44
45 private ExtendedIterator filter( final Stage allStages )
46 {
47 return new NiceIterator()
49 {
50 private Pipe complete;
51
52 private void ensurePipe()
53 { if (complete == null) complete = allStages.deliver( new BufferPipe() ); }
54
55 public void close() { allStages.close(); clearPipe(); }
56
57 public Object  next() { ensurePipe(); return complete.get(); }
58
59 public boolean hasNext() { ensurePipe(); return complete.hasNext(); }
60
61 private void clearPipe()
62 {
63 int count = 0;
64 while (hasNext()) { count += 1; next(); }
65 }
66 };
67 }
68
69 public static Cons cons( Triple pattern, Object cons )
70 { return new Cons( pattern, (Cons) cons ); }
71
72 private static class Cons
73 {
74 Triple head;
75 Cons tail;
76 Cons( Triple head, Cons tail ) { this.head = head; this.tail = tail; }
77 static int size( Cons L ) { int n = 0; while (L != null) { n += 1; L = L.tail; } return n; }
78 }
79
80 private void addStages( ArrayList stages, NamedGraphMap arguments, Mapping map )
81 {
82 Iterator it2 = triples.entrySetIterator();
83 while (it2.hasNext())
84 {
85 Map.Entry e = (Map.Entry) it2.next();
86 String name = (String ) e.getKey();
87 Cons nodeTriples = (Cons) e.getValue();
88 Graph g = arguments.get( name );
89 int nBlocks = Cons.size( nodeTriples ), i = nBlocks;
90 Triple [] nodes = new Triple[nBlocks];
91 while (nodeTriples != null)
92 {
93 nodes[--i] = nodeTriples.head;
94 nodeTriples = nodeTriples.tail;
95 }
96 nodes = sortTriples( nodes );
97 Stage next = g.queryHandler().patternStage( map, constraint, nodes );
98 stages.add( next );
99 }
100 }
101
102 private Triple [] sortTriples( Triple [] ts )
103 { return sortMethod.sort( ts ); }
104
105 private Stage connectStages( ArrayList stages, int count )
106 {
107 Stage current = Stage.initial( count );
108 for (int i = 0; i < stages.size(); i += 1)
109 current = ((Stage) stages.get( i )).connectFrom( current );
110 return current;
111 }
112 }
113
114 |
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