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1
21 package com.db4o.nativequery.optimization;
22
23 import com.db4o.foundation.*;
24 import com.db4o.nativequery.expr.*;
25 import com.db4o.nativequery.expr.cmp.*;
26 import com.db4o.query.*;
27
28 public class SODAQueryBuilder {
29 private static class SODAQueryVisitor implements ExpressionVisitor {
30 private Object  _predicate;
31 private Query _query;
32 private Constraint _constraint;
33
34 SODAQueryVisitor(Query query, Object predicate) {
35 _query=query;
36 _predicate = predicate;
37 }
38
39 public void visit(AndExpression expression) {
40 expression.left().accept(this);
41 Constraint left=_constraint;
42 expression.right().accept(this);
43 left.and(_constraint);
44 _constraint=left;
45 }
46
47 public void visit(BoolConstExpression expression) {
48 }
49
50 public void visit(OrExpression expression) {
51 expression.left().accept(this);
52 Constraint left=_constraint;
53 expression.right().accept(this);
54 left.or(_constraint);
55 _constraint=left;
56 }
57
58 public void visit(ComparisonExpression expression) {
59 Query subQuery=_query;
60 Iterator4 fieldNameIterator = fieldNames(expression.left());
61 while(fieldNameIterator.moveNext()) {
62 subQuery=subQuery.descend((String )fieldNameIterator.current());
63 }
64 ComparisonQueryGeneratingVisitor visitor = new ComparisonQueryGeneratingVisitor(_predicate);
65 expression.right().accept(visitor);
66 _constraint=subQuery.constrain(visitor.value());
67 if(!expression.op().equals(ComparisonOperator.EQUALS)) {
68 if(expression.op().equals(ComparisonOperator.GREATER)) {
69 _constraint.greater();
70 }
71 else if(expression.op().equals(ComparisonOperator.SMALLER)) {
72 _constraint.smaller();
73 }
74 else if(expression.op().equals(ComparisonOperator.CONTAINS)) {
75 _constraint.contains();
76 }
77 else if(expression.op().equals(ComparisonOperator.STARTSWITH)) {
78 _constraint.startsWith(true);
79 }
80 else if(expression.op().equals(ComparisonOperator.ENDSWITH)) {
81 _constraint.endsWith(true);
82 }
83 else {
84 throw new RuntimeException ("Can't handle constraint: "+expression.op());
85 }
86 }
87 }
88
89 public void visit(NotExpression expression) {
90 expression.expr().accept(this);
91 _constraint.not();
92 }
93
94 private Iterator4 fieldNames(FieldValue fieldValue) {
95 Collection4 coll=new Collection4();
96 ComparisonOperand curOp=fieldValue;
97 while(curOp instanceof FieldValue) {
98 FieldValue curField=(FieldValue)curOp;
99 coll.prepend(curField.fieldName());
100 curOp=curField.parent();
101 }
102 return coll.iterator();
103 }
104 }
105
106 public void optimizeQuery(Expression expr, Query query, Object predicate) {
107 expr.accept(new SODAQueryVisitor(query, predicate));
108 }
109 }
110 |
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