Source Code Cross Referenced for SortExpression.java in  » XML » saxonb » net » sf » saxon » sort » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » XML » saxonb » net.sf.saxon.sort 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        package net.sf.saxon.sort;
002:
003:        import net.sf.saxon.expr.*;
004:        import net.sf.saxon.om.EmptyIterator;
005:        import net.sf.saxon.om.NamePool;
006:        import net.sf.saxon.om.SequenceIterator;
007:        import net.sf.saxon.trans.XPathException;
008:        import net.sf.saxon.type.ItemType;
009:        import net.sf.saxon.type.TypeHierarchy;
010:        import net.sf.saxon.value.Cardinality;
011:        import net.sf.saxon.value.Value;
012:
013:        import java.io.PrintStream;
014:        import java.util.ArrayList;
015:        import java.util.Iterator;
016:        import java.util.List;
017:
018:        /**
019:         * Expression equivalent to the imaginary syntax
020:         * expr sortby (sort-key)+
021:         */
022:
023:        public class SortExpression extends ComputedExpression {
024:
025:            private Expression select = null;
026:            private SortKeyDefinition[] sortKeys = null;
027:            private FixedSortKeyDefinition[] fixedSortKeys = null;
028:
029:            public SortExpression(Expression select,
030:                    SortKeyDefinition[] sortKeys) {
031:                this .select = select;
032:                this .sortKeys = sortKeys;
033:                boolean fixed = true;
034:                for (int i = 0; i < sortKeys.length; i++) {
035:                    if (!(sortKeys[i] instanceof  FixedSortKeyDefinition)) {
036:                        fixed = false;
037:                        break;
038:                    }
039:                    ;
040:                    sortKeys[i].setParentExpression(this );
041:                }
042:                if (fixed) {
043:                    fixedSortKeys = new FixedSortKeyDefinition[sortKeys.length];
044:                    System.arraycopy(sortKeys, 0, fixedSortKeys, 0,
045:                            sortKeys.length);
046:                }
047:                Iterator children = iterateSubExpressions();
048:                while (children.hasNext()) {
049:                    Expression exp = (Expression) children.next();
050:                    adoptChildExpression(exp);
051:                }
052:            }
053:
054:            /**
055:             * Get the immediate sub-expressions of this expression. Default implementation
056:             * returns a zero-length array, appropriate for an expression that has no
057:             * sub-expressions.
058:             * @return an iterator containing the sub-expressions of this expression
059:             */
060:
061:            public Iterator iterateSubExpressions() {
062:                List list = new ArrayList(8);
063:                list.add(select);
064:                for (int i = 0; i < sortKeys.length; i++) {
065:                    list.add(sortKeys[i].getSortKey());
066:                    Expression e = sortKeys[i].order;
067:                    if (e != null && !(e instanceof  Value)) {
068:                        list.add(e);
069:                    }
070:                    e = sortKeys[i].caseOrder;
071:                    if (e != null && !(e instanceof  Value)) {
072:                        list.add(e);
073:                    }
074:                    e = sortKeys[i].dataTypeExpression;
075:                    if (e != null && !(e instanceof  Value)) {
076:                        list.add(e);
077:                    }
078:                    e = sortKeys[i].language;
079:                    if (e != null && !(e instanceof  Value)) {
080:                        list.add(e);
081:                    }
082:                    e = sortKeys[i].collationName;
083:                    if (e != null && !(e instanceof  Value)) {
084:                        list.add(e);
085:                    }
086:                }
087:                return list.iterator();
088:            }
089:
090:            /**
091:             * Simplify an expression
092:             */
093:
094:            public Expression simplify(StaticContext env) throws XPathException {
095:                select = select.simplify(env);
096:                return this ;
097:            }
098:
099:            /**
100:             * Type-check the expression
101:             */
102:
103:            public Expression typeCheck(StaticContext env,
104:                    ItemType contextItemType) throws XPathException {
105:                select = select.typeCheck(env, contextItemType);
106:                return this ;
107:            }
108:
109:            /**
110:             * Perform optimisation of an expression and its subexpressions.
111:             * <p/>
112:             * <p>This method is called after all references to functions and variables have been resolved
113:             * to the declaration of the function or variable, and after all type checking has been done.</p>
114:             *
115:             * @param opt             the optimizer in use. This provides access to supporting functions; it also allows
116:             *                        different optimization strategies to be used in different circumstances.
117:             * @param env             the static context of the expression
118:             * @param contextItemType the static type of "." at the point where this expression is invoked.
119:             *                        The parameter is set to null if it is known statically that the context item will be undefined.
120:             *                        If the type of the context item is not known statically, the argument is set to
121:             *                        {@link net.sf.saxon.type.Type#ITEM_TYPE}
122:             * @return the original expression, rewritten if appropriate to optimize execution
123:             * @throws net.sf.saxon.trans.StaticError if an error is discovered during this phase
124:             *                                        (typically a type error)
125:             */
126:
127:            public Expression optimize(Optimizer opt, StaticContext env,
128:                    ItemType contextItemType) throws XPathException {
129:                if (Cardinality.allowsMany(select.getCardinality())) {
130:                    return this ;
131:                } else {
132:                    return select;
133:                }
134:            }
135:
136:            /**
137:             * Offer promotion for this subexpression. The offer will be accepted if the subexpression
138:             * is not dependent on the factors (e.g. the context item) identified in the PromotionOffer.
139:             * By default the offer is not accepted - this is appropriate in the case of simple expressions
140:             * such as constant values and variable references where promotion would give no performance
141:             * advantage. This method is always called at compile time.
142:             *
143:             * @param offer details of the offer, for example the offer to move
144:             *              expressions that don't depend on the context to an outer level in
145:             *              the containing expression
146:             * @return if the offer is not accepted, return this expression unchanged.
147:             *         Otherwise return the result of rewriting the expression to promote
148:             *         this subexpression
149:             * @throws net.sf.saxon.trans.XPathException
150:             *          if any error is detected
151:             */
152:
153:            public Expression promote(PromotionOffer offer)
154:                    throws XPathException {
155:                Expression exp = offer.accept(this );
156:                if (exp != null) {
157:                    return exp;
158:                } else {
159:                    select = doPromotion(select, offer);
160:                    for (int i = 0; i < sortKeys.length; i++) {
161:                        sortKeys[i].setSortKey((sortKeys[i].getSortKey()
162:                                .promote(offer)));
163:                        if (sortKeys[i].caseOrder != null) {
164:                            sortKeys[i].caseOrder = sortKeys[i].caseOrder
165:                                    .promote(offer);
166:                        }
167:                        if (sortKeys[i].dataTypeExpression != null) {
168:                            sortKeys[i].dataTypeExpression = sortKeys[i].dataTypeExpression
169:                                    .promote(offer);
170:                        }
171:                        if (sortKeys[i].language != null) {
172:                            sortKeys[i].language = sortKeys[i].language
173:                                    .promote(offer);
174:                        }
175:                        if (sortKeys[i].collationName != null) {
176:                            sortKeys[i].collationName = sortKeys[i].collationName
177:                                    .promote(offer);
178:                        }
179:                    }
180:                    return this ;
181:                }
182:            }
183:
184:            /**
185:             * Test whether a given expression is one of the sort keys
186:             */
187:
188:            public boolean isSortKey(Expression child) {
189:                for (int i = 0; i < sortKeys.length; i++) {
190:                    Expression exp = sortKeys[i].getSortKey();
191:                    if (exp == child) {
192:                        return true;
193:                    }
194:                }
195:                return false;
196:            }
197:
198:            /**
199:             * Determine the static cardinality
200:             */
201:
202:            public int computeCardinality() {
203:                return select.getCardinality();
204:            }
205:
206:            /**
207:             * Determine the data type of the items returned by the expression, if possible
208:             * @return a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE,
209:             * or Type.ITEM (meaning not known in advance)
210:             * @param th
211:             */
212:
213:            public ItemType getItemType(TypeHierarchy th) {
214:                return select.getItemType(th);
215:            }
216:
217:            /**
218:             * Get the static properties of this expression (other than its type). The result is
219:             * bit-significant. These properties are used for optimizations. In general, if
220:             * property bit is set, it is true, but if it is unset, the value is unknown.
221:             */
222:
223:            public int computeSpecialProperties() {
224:                int props = 0;
225:                if ((select.getSpecialProperties() & StaticProperty.CONTEXT_DOCUMENT_NODESET) != 0) {
226:                    props |= StaticProperty.CONTEXT_DOCUMENT_NODESET;
227:                }
228:                if ((select.getSpecialProperties() & StaticProperty.SINGLE_DOCUMENT_NODESET) != 0) {
229:                    props |= StaticProperty.SINGLE_DOCUMENT_NODESET;
230:                }
231:                if ((select.getSpecialProperties() & StaticProperty.NON_CREATIVE) != 0) {
232:                    props |= StaticProperty.NON_CREATIVE;
233:                }
234:                return props;
235:            }
236:
237:            /**
238:             * Enumerate the results of the expression
239:             */
240:
241:            public SequenceIterator iterate(XPathContext context)
242:                    throws XPathException {
243:
244:                SequenceIterator iter = select.iterate(context);
245:                if (iter instanceof  EmptyIterator) {
246:                    return iter;
247:                }
248:                XPathContext xpc = context.newMinorContext();
249:                xpc.setOrigin(this );
250:
251:                FixedSortKeyDefinition[] reducedSortKeys;
252:                if (fixedSortKeys != null) {
253:                    reducedSortKeys = fixedSortKeys;
254:                } else {
255:                    reducedSortKeys = new FixedSortKeyDefinition[sortKeys.length];
256:                    for (int s = 0; s < sortKeys.length; s++) {
257:                        reducedSortKeys[s] = sortKeys[s].reduce(xpc);
258:                    }
259:                }
260:                iter = new SortedIterator(xpc, iter, reducedSortKeys);
261:                return iter;
262:            }
263:
264:            public void display(int level, NamePool pool, PrintStream out) {
265:                out.println(ExpressionTool.indent(level) + "sort");
266:                select.display(level + 1, pool, out);
267:            }
268:        }
269:
270:        //
271:        // The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
272:        // you may not use this file except in compliance with the License. You may obtain a copy of the
273:        // License at http://www.mozilla.org/MPL/
274:        //
275:        // Software distributed under the License is distributed on an "AS IS" basis,
276:        // WITHOUT WARRANTY OF ANY KIND, either express or implied.
277:        // See the License for the specific language governing rights and limitations under the License.
278:        //
279:        // The Original Code is: all this file.
280:        //
281:        // The Initial Developer of the Original Code is Michael H. Kay
282:        //
283:        // Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
284:        //
285:        // Contributor(s): none.
286:        //
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